rotating electrical machines

Abstract

To provide a rotary electric machine which decreases a back electromotive voltage generated in a stator coil, can make a maximal value in the vicinity of a wave height close to an amplitude of a dominant wave, effectively utilize a coil applied voltage upper limit to an inverter DC voltage and increase torque.SOLUTION: A rotary electric machine 10 comprises a stator 20 having a slot 21, and a rotor 30 having magnetic poles 33 constructed by burying a magnet 31 in a flux barrier 32. Each magnetic pole 33 of a magnetic pole pair neighboring in a circumferential direction of the rotor 30 has a bridge 35 at an extending tip region 34 of the flux barrier 32. The bridge 35 is any of an external bridge 35a arranged on the surface of the rotor 30 and a middle bridge 35b arranged in a further inner diameter side than the external bridge 35a. The number of the external bridge 35a and the middle bridge 35b in the magnetic pole pair are same. Arrangement of the external bridge 35a and the middle bridge 35b is symmetric to one of d-axis and q-axis and asymmetric to the other axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine having a rotor structure capable of reducing back electromotive force. [Background technology]

[0002] Rotating electric machines are used as electric motors for trains and automobiles. Typically, a rotating electric machine has a cylindrical stator and a rotor that is rotatably supported inside the stator. The rotor is formed by stacking electromagnetic steel sheets in the direction of the rotation axis. Multiple magnets are embedded in these electromagnetic steel sheets, and magnetic poles of different magnetic properties are arranged alternately in the circumferential direction of rotation.

[0003] In a rotating electric machine consisting of a rotor, stator, etc., a back electromotive force (line voltage) is generated in the stator coil due to magnetic changes caused by the rotation of the rotor. If the maximum value of the back electromotive force becomes large, it becomes necessary to limit the upper limit of the voltage applied to the coil, which poses the problem of a decrease in motor torque.

[0004] Patent Document 1 describes a permanent magnet rotating electric machine in which deep recesses are provided on the surface on the q-axis at the outer periphery of the rotor in order to reduce the maximum value of the line voltage without reducing the torque constant. Patent Document 2 describes a rotating electric machine in which recesses are provided on the surface of a rotor core surrounded by magnets at each of the south and north poles of the rotor surface in order to reduce torque ripple. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-16189 [Patent Document 2] Patent No. 2017-70040 Summary of the Invention [Problem to be solved by the invention]

[0006] The technique in Patent Document 1 provides a magnetic resistance on the q-axis between the magnetic poles, which is difficult to apply to rotating electrical machines that utilize reluctance torque.The technique in Patent Document 2 provides a magnetic resistance separate from the flux barrier, which raises concerns about an average decrease in torque. [Means for solving the problem]

[0007] A rotating electric machine according to the present invention includes a stator having slots, and a rotor having magnetic poles formed by magnets embedded in a flux barrier. the black barrier extends along the circumferential direction of the rotor around the d-axis and has tip regions on both sides thereof that face the outer circumferential surface of the rotor, the magnets are embedded in portions of the rotor that are along the circumferential direction, and the tip regions are formed as spaces in which the magnets are not embedded, The magnetic poles of the magnetic pole pairs adjacent to each other in the circumferential direction of the rotor are Address The bridge has a bridge at the end region, the bridge having: formed on the outer peripheral surface of the rotor in the tip region The outer bridge and the inner diameter side of the outer bridge The intermediate portion of the tip region The number of outer bridges and middle bridges in a magnetic pole pair is the same, and the arrangement of the outer bridges and middle bridges is symmetrical with respect to one of the d-axis and q-axis, and asymmetrical with respect to the other axis.

[0008] Here, it is preferable that the arrangement of the outer bridge and the center bridge at one pole of the magnetic pole pair is asymmetric with respect to the d-axis, and that the arrangement of the outer bridge and the center bridge at the other pole of the magnetic pole pair is symmetric with respect to the q-axis as the arrangement at one pole of the magnetic pole pair.

[0009] Also ,before At one of the poles of the pole pair, Only the outer bridge Arranged symmetrically with respect to the d axis ,before At the other pole of the pole pair, Only the middle bridge It is preferable that they are arranged symmetrically with respect to the d axis.

[0010] Here, the rotor of the rotating electric machine has a plurality of flux barriers in the radial direction, and the above-mentioned arrangement of the outer bridge and middle bridge is preferably applied to the flux barrier arranged on the inner, outermost side of the flux barrier.

[0011] Furthermore, when the open angle between adjacent teeth is α and the angle formed by a line connecting the circumferential center of two bridges sandwiching the d-axis at the magnetic pole and the center of the rotation axis is β, it is preferable that the rotating electric machine satisfy α×N≦β≦α×(N+1), where N is an integer greater than or equal to 1.

[0012] Furthermore, the rotor of the rotating electrical machine may be formed by stacking partial rotors in the direction of the rotation axis, with the outer bridges and middle bridges interchanged with each other. [Effects of the Invention]

[0013] The rotating electric machine according to the present invention can suppress the back electromotive force that accompanies rotor rotation. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a partial cross-sectional view of a rotating electric machine according to the present invention; [Figure 2] 4 shows the relationship between the tooth opening angle and the bridge opening angle of the rotating electric machine of the present invention. [Figure 3] 4 is a cross-sectional view showing the arrangement of bridges in the magnetic pole pairs of the rotors of Examples 1 to 4. FIG. [Figure 4] 10 is a cross-sectional view showing the arrangement of bridges in the magnetic pole pairs of the rotors of Comparative Examples 1 to 3. FIG. [Figure 5] 10 is a cross-sectional view showing the arrangement of bridges in the magnetic pole pairs of the rotors of Comparative Examples 4 and 5. FIG. [Figure 6] 10A and 10B are diagrams showing back electromotive voltage waveforms in Comparative Examples 1 to 3, where (a) is a waveform diagram for one electrical angle cycle, and (b) is an enlarged diagram for an electrical angle of 60°±30°. [Figure 7] 6. The back electromotive voltage waveforms for Examples 1 and 4 and Comparative Examples 1 and 2 are similar to those in FIG. [Figure 8] 1A and 1B are diagrams comparing the counter electromotive force waveforms of Examples 1 to 4, where (a) is a diagram comparing Examples 1 and 2, and (b) is a diagram comparing Examples 3 and 4. FIG. [Figure 9] 10 is a graph comparing peak voltage / fundamental wave amplitude between an example and a comparative example. [Figure 10]6. The back electromotive voltage waveforms for Example 1 and Comparative Examples 4 and 5 are similar to those in FIG. [Figure 11] 1 is a diagram illustrating the positions where peak voltages occur in Example 1 and Comparative Examples 1 and 2. FIG. [Figure 12] 10 shows the analysis results of the magnetic flux density distribution in Example 1. [Figure 13] 10 shows the analysis results of the magnetic flux density distribution in Comparative Example 1. [Figure 14] 10 is an analysis result of the magnetic flux density distribution in Comparative Example 2. [Figure 15] 7 shows a back electromotive force waveform similar to that shown in FIG. 6 for a configuration in which Example 1 and the comparative example are alternately stacked. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating understanding of the present invention, and can be appropriately changed according to the application, purpose, specifications, etc. Furthermore, it is originally anticipated that the components of the embodiments and modifications described below can be selectively combined.

[0016] Fig. 1 shows a partial cross-sectional view of a rotating electric machine 10 of the present invention. The rotating electric machine 10 includes a stator 20 and a rotor 30. The rotating electric machine 10 is an electric motor that generates a rotating magnetic field in the stator 20 and rotates the rotor 30 about a rotation axis. Fig. 1 shows a cross-section of a sector-shaped portion of the stator 20 and rotor 30.

[0017] The stator 20 has a hollow cylindrical shape. The stator 20 is formed by stacking multiple electromagnetic steel plates along the rotation axis direction. The stator 20 has a structure in which multiple slots 21 and teeth 22 are arranged alternately at equal intervals in the circumferential direction. Coils are wound in the slots 21. The teeth 22 face the outer periphery of the rotor 30 and act as surfaces that receive magnetic flux from the rotor 30. A back yoke 23 is arranged on the outer periphery of the slots 21 and teeth 22. The back yoke 23 is an iron core that connects the magnetic flux between each tooth 22 and forms a magnetic circuit.

[0018] The rotor 30 has a cylindrical shape. The rotor 30 is arranged rotatably around the rotation axis inside the hollow cylindrical stator 20. The rotor 30 is arranged with a gap between its outer circumferential surface and the inner circumferential surface of the stator 20. The rotor 30 is formed by stacking multiple electromagnetic steel plates along the rotation axis direction.

[0019] The rotor 30 has a flux barrier 32 with the magnets 31 embedded therein. The flux barrier 32 is an area with a lower magnetic permeability than the electromagnetic steel sheets that make up the rotor 30, and is formed, for example, by a space provided inside the rotor 30. The flux barrier 32 prevents the magnetic flux from the magnets 31 from leaking out from the side surfaces of the rotor 30, thereby increasing the magnetic flux density on the outer circumferential surface of the rotor 30.

[0020] A plurality of flux barriers 32 may be provided for each magnetic pole. For example, a plurality of flux barriers 32 may be provided in the radial direction of the rotor 30. In this embodiment, the rotor 30 has two flux barriers, a first flux barrier 32a and a second flux barrier 32b, arranged along the radial direction.

[0021] The magnets 31 embedded in the flux barriers 32 form magnetic poles 33 in the rotor 30. The magnets 31 are arranged so that the direction of magnetic flux in each magnetic pole 33 is oriented in the radial direction of the rotor 30. In other words, the center of magnetic flux in each magnetic pole 33 coincides with the d-axis. The magnets 31 are arranged so that the magnetization directions of adjacent magnetic poles 33 in the circumferential direction are different, and magnetic pole pairs, south magnetic poles 33S and north magnetic poles 33N, are formed alternately along the circumferential direction. In the rotor 30, the centers of the south magnetic poles 33S and north magnetic poles 33N coincide with the q-axis.

[0022] The flux barrier 32 extends circumferentially around the rotor 30, with both ends curved toward the outer circumferential surface of the rotor 30. A bridge 35 is formed in end regions 34 (first end region 34a, second end region 34b) on both ends of the first flux barrier 32a. The first end region 34a of the first flux barrier 32a in one magnetic pole 33 is adjacent to the second end region 34b of the first flux barrier 32a in another magnetic pole 33 adjacent to that magnetic pole 33.

[0023] In this embodiment, it is preferable that both ends of the first flux barrier 32a, which is provided on the outermost side of the rotor 30 among the flux barriers 32, be the tip regions 34 (first tip region 34a, second tip region 34b). However, both ends of other flux barriers, such as the second flux barrier 32b, may also be the tip regions 34 (first tip region 34a, second tip region 34b).

[0024] In this embodiment, two types of bridges 35 are used: an outer bridge 35a and a middle bridge 35b. The outer bridge 35a is a portion that connects the outer peripheral surface of the rotor 30 and the tip of the flux barrier 32 near the outer peripheral surface of the rotor 30 where no recesses or the like are provided. The middle bridge 35b is a portion that connects a recess provided on the outer peripheral surface of the rotor 30 or a gap provided inside the rotor 30 to the tip of the flux barrier 32. In other words, due to the recess provided on the outer peripheral surface of the rotor 30 or the gap provided inside the rotor 30, the middle bridge 35b is located more inward than the outer bridge 35a with respect to the outer peripheral surface of the rotor 30.

[0025] In each magnetic pole 33, the first tip region 34a and the second tip region 34b of the first flux barrier 32a are positioned symmetrically with respect to the d-axis. The structures of the magnetic poles 33 are symmetrical with respect to the q-axis, except for the configuration of the bridges 35. Either an outer bridge 35a or an inner bridge 35b is applied to the first tip region 34a and the second tip region 34b, respectively. In consideration of the rotational balance of the rotor 30, it is preferable to arrange the bridges 35 periodically along the circumferential direction.

[0026] FIG. 2 shows the relationship between the spacing angle of adjacent teeth 22 and the bridge spacing angle of bridges 35. Here, the angle formed by a line connecting the radial center lines of adjacent teeth 22 and the rotation axis is defined as the tooth spacing angle α. When outer bridges 35a are arranged in the first tip region 34a and the second tip region 34b, the angle formed by a line connecting the circumferential center of the outer bridge 35a and the center of the rotation axis is defined as the bridge spacing angle β. The bridge spacing angle β and tooth spacing angle α of the rotating electric machine 10 of the present invention are formed to satisfy α×N≦β≦α×(N+1), where N is an integer greater than or equal to 1. Although FIG. 2 shows that an intermediate bridge 35b is arranged in the second tip region 34b, the bridge spacing angle β is calculated assuming that the outer bridge 35a is arranged therein.

[0027] In this embodiment, the open angle α of the teeth 22 is set to 7.5°, and the coefficient N is set to 2. Therefore, the bridge open angle β of the bridge 35 is set to satisfy the condition 15°≦β≦22.5°. However, the relationship between the open angle α of the teeth 22 and the bridge open angle β of the bridge 35 is not limited to this, and it is sufficient if the above formula is satisfied.

[0028] The symmetry (symmetrical arrangement) in the arrangement of the bridges 35 is defined as follows. "Symmetrical with respect to the d-axis" means that the types of bridges 35 arranged in the first tip region 34a and the second tip region 34b of the flux barrier 32 are the same. "Asymmetric with respect to the d-axis" means that the types of bridges 35 arranged in the first tip region 34a and the second tip region 34b of the flux barrier 32 are different. "Symmetrical with respect to the q axis" means that in the magnetic pole pair, the same type of bridge 35 is arranged in the tip region 34 of each magnetic pole 33 at a position symmetrical with respect to the q axis. "Asymmetric with respect to the q axis" means that in a magnetic pole pair, different types of bridges 35 are arranged in the tip regions 34 of the magnetic poles 33 at positions symmetric with respect to the q axis.

[0029] The present invention was made with an eye on the fact that the outer bridge 35a and the center bridge 35b, which are arranged at the south magnetic pole 33S and the north magnetic pole 33N of the magnetic pole pair, have a specific arrangement symmetry with respect to the d-axis and q-axis, thereby suppressing back electromotive force.

[0030] 3(a) to 3(d), the arrangement of the bridges 35 in the rotor 30 will be described. Figures 3(a) to 3(d) show the arrangements of the outer bridges 35a and the middle bridges 35b in Examples 1 to 4, respectively.

[0031] Example 1 In Example 1, a center bridge 35b is disposed in the first tip region 34a of the south magnetic pole 33S. An outer bridge 35a is disposed in the second tip region 34b of the south magnetic pole 33S. An outer bridge 35a is disposed in the first tip region 34a of the north magnetic pole 33N. A center bridge 35b is disposed in the second tip region 34b of the north magnetic pole 33N.

[0032] In other words, different types of bridges 35 are arranged in the first tip region 34a of the S magnetic pole 33S and the first tip region 34a of the N magnetic pole 33N, and different types of bridges 35 are arranged in the second tip region 34b of the S magnetic pole 33S and the second tip region 34b of the N magnetic pole 33N.

[0033] Hereinafter, the arrangement of bridges 35 will be expressed by sequentially arranging the initial letters of the types of bridges 35 arranged in the first tip region 34a and second tip region 34b of the south magnetic pole 33S and the first tip region 34a and second tip region 34b of the north magnetic pole 33N of the magnetic pole pair. Specifically, the arrangement of bridges 35 in Example 1 will be expressed as "inside-outside-inside."

[0034] <Example 2> In Example 2, the outer bridge 35a and the inner bridge 35b in Example 1 are interchanged. That is, the arrangement of the bridges 35 in Example 2 is "outer-in-in-outer."

[0035] Example 3 In Example 3, a center bridge 35b is disposed between the first and second tip regions 34a, 34b of the south magnetic pole 33S. An outer bridge 35a is disposed between the first and second tip regions 34a, 34b of the north magnetic pole 33N.

[0036] In other words, the same type of bridges 35 are arranged in the first tip region 34a and the second tip region 34b of the S magnetic pole 33S, and a different type of bridge 35 is arranged in the tip region 34 of the N magnetic pole 33N than in the tip region 34 of the S magnetic pole 33S. The arrangement structure of the bridges 35 in Example 3 is "middle-middle-outside-outside".

[0037] Example 4 Example 4 has a configuration in which the outer bridge 35a and the center bridge 35b in Example 3 are interchanged. That is, the arrangement of the bridges 35 in Example 4 is "outside-outside-center-center."

[0038] <Conditions for bridge placement structure> The following two conditions are common to the magnetic pole pairs in Examples 1 to 4. Condition (1): The number of outer bridges 35a and the number of middle bridges 35b are the same. Condition (2): The arrangement of the outer bridges 35a and the center bridges 35b is symmetrical with respect to either the d axis or the q axis, and is asymmetrical with respect to the other axis. In the magnetic pole pair, by configuring the outer bridge 35a and the center bridge 35b in this way, it is possible to suppress the counter electromotive force.

[0039] Next, as comparative examples, arrangement structures of bridges 35 that do not satisfy the above condition (2) are shown in Figures 4 and 5. Figures 4(a), 4(b), 4(c), 5(a), and 5(b) show the arrangements of the outer bridges 35a and middle bridges 35b of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5, respectively.

[0040] <Comparative Example 1> Outer bridges 35a are arranged in the first and second tip regions 34a, 34b of the south magnetic pole 33S in comparative example 1. Outer bridges 35a are also arranged in the first and second tip regions 34a, 34b of the north magnetic pole 33N. In other words, the arrangement of the bridges 35 in comparative example 1 is "outside-outside-outside."

[0041] <Comparative Example 2> In Comparative Example 2, center bridges 35b are arranged in the first and second tip regions 34a, 34b of the south magnetic pole 33S. Center bridges 35b are also arranged in the first and second tip regions 34a, 34b of the north magnetic pole 33N. In other words, the arrangement of bridges 35 in Comparative Example 2 is "center-center-center-center."

[0042] <Comparative Example 3> Both outer bridges 35a and center bridges 35b are arranged in all tip regions 34 of the south magnetic pole 33S and north magnetic pole 33N of comparative example 3. In other words, comparative example 3 has the bridge 35 arrangement structures of both comparative examples 1 and 2. The bridge 35 arrangement structure of comparative example 3 is "outside-outside-outside / center-center-center-center."

[0043] <Comparative Example 4> An outer bridge 35a is arranged in the first tip region 34a of the S magnetic pole 33S of Comparative Example 4. A center bridge 35b is arranged in the second tip region 34b of the S magnetic pole 33S. An outer bridge 35a of the same type as the first tip region 34a of the S magnetic pole 33S is arranged in the first tip region 34a of the N magnetic pole 33N. A center bridge 35b of the same type as the second tip region 34b of the S magnetic pole 33S is arranged in the second tip region 34b of the N magnetic pole 33N. In other words, the arrangement structure of the bridges 35 in Comparative Example 4 is "outside-inside-outside-inside."

[0044] Comparative Example 5 has a configuration in which the outer bridge 35a and the inner bridge 35b in Comparative Example 4 are interchanged. That is, the arrangement of the bridges 35 in Comparative Example 5 is "inside-outside-inside-outside."

[0045] As described above, in Comparative Examples 1 to 5, the number of outer bridges 35a and the number of center bridges 35b in the magnetic pole pairs are the same, and thus condition (1) is satisfied. On the other hand, the outer bridges 35a and the center bridges 35b are both symmetrical or both asymmetrical with respect to the d-axis and the q-axis, and thus condition (2) is not satisfied.

[0046] Table 1 shows the arrangements of the outer bridges 35a and the center bridges 35b in the magnetic pole pairs of Examples 1 to 4 and Comparative Examples 1 to 5.

[0047] [Table 1]

[0048] Next, a description will be given of the difference in the generation of back electromotive force depending on the arrangement of the bridge 35. Figures 6 to 9 show simulation results of back electromotive force in the arrangements of the bridge 35 of the example and the comparative example.

[0049] Fig. 6 shows the simulation results of the back electromotive force in the UV line voltage for Comparative Examples 1 to 3. In Fig. 6, the horizontal axis represents the electrical angle, and the vertical axis represents the back electromotive force in pu units. Fig. 6(a) shows the back electromotive force waveform for one electrical angle cycle, and Fig. 6(b) is an enlarged view of an electrical angle of 60°±30°, showing the waveform near the maximum amplitude of the fundamental wave.

[0050] In all of Comparative Examples 1 to 3, the peak voltage value was greater than the maximum value of the fundamental voltage at an electrical angle of around 60°. Therefore, it was necessary to suppress the upper limit of the voltage applied to the coil, and the inverter DC voltage could not be effectively utilized.

[0051] In Comparative Example 2, the voltage increased near the electrical angle when the d-axis was parallel to the central axis of the teeth 22, i.e., near the electrical angle (60°) at which the fundamental wave voltage of the line voltage was at its maximum value. On the other hand, the voltage decreased near 15° before and after the electrical angle of 60°, i.e., near the electrical angle corresponding to the electrical angle when the d-axis rotates from the central axis of the teeth 22 to the central axis of the slot 21.

[0052] In Comparative Examples 1 and 3, the voltage increased at an electrical angle that was approximately 15° shifted from the electrical angle when the d-axis was parallel to the central axis of slot 21, i.e., the electrical angle of 60° at which the fundamental wave voltage was at its maximum value, which corresponds to the electrical angle when the d-axis rotates from the central axis of tooth 22 to the central axis of slot 21.

[0053] In Comparative Example 3, the maximum value of the fundamental wave voltage near an electrical angle of 60° was smaller. As a result, the torque of the rotating electric machine 10 in Comparative Example 3 was reduced. In Comparative Example 3, both outer bridges 35a and inner bridges 35b were arranged in all tip regions 34 of the south magnetic poles 33S and north magnetic poles 33N, and the total number of bridges 35 was large, so it is presumed that this was because the magnetic flux of the magnets 31 was confined within the rotor 30, reducing the amount of linkage with the stator 20. In Comparative Examples 2 and 1, which had fewer total numbers of bridges 35 than Comparative Example 3, the torque of the rotating electric machine 10 was greater than in Comparative Example 3. The torque ratio of Comparative Examples 1 to 3 was Comparative Example 2:Comparative Example 1:Comparative Example 3 = 100.0:98.5:96.2.

[0054] Fig. 7 shows the simulation results of the back electromotive force in the UV line voltage for Examples 1 and 4 and Comparative Examples 1 and 2. In Fig. 7, the horizontal axis represents the electrical angle, and the vertical axis represents the back electromotive force in pu units. Fig. 7(a) shows the back electromotive force waveform for one electrical angle cycle, and Fig. 7(b) is an enlarged view of an electrical angle of 60°±30°, showing the waveform near the maximum amplitude of the fundamental wave.

[0055] In Examples 1 and 4, the peak voltage near an electrical angle of 60° could be reduced compared to Comparative Example 1, and the peak voltage near an electrical angle of 60°±15° could be reduced compared to Comparative Example 2. That is, in Examples 1 and 4, the peak voltage could be reduced overall.

[0056] 8(a) shows the simulation results of the back electromotive force in the UV phase-line voltage in Examples 1 and 2, and FIG. 8(b) shows the simulation results of the back electromotive force in the UV phase-line voltage in Examples 3 and 4. The arrangement of the bridges 35 in Example 2 is the same as that of the bridges 35 in Example 1, rotated circumferentially by one magnetic pole, and therefore Example 2 produced substantially the same back electromotive force waveform as Example 1. Furthermore, the arrangement of the bridges 35 in Example 4 is the same as that of the bridges 35 in Example 3, rotated circumferentially by one magnetic pole, and therefore Example 3 produced substantially the same back electromotive force waveform as Example 4.

[0057] Examples 1 to 4 are characterized by having a counter electromotive force intermediate between that of Comparative Example 1 and Comparative Example 2. Specifically, by adjusting the harmonic voltage, it was possible to make the maximum value of the counter electromotive force close to the maximum value of the fundamental wave.

[0058] FIG. 9 shows the calculation results of the value obtained by dividing the peak voltage by the amplitude of the fundamental wave (peak voltage / fundamental wave amplitude). In the rotating electric machine 10, torque increases according to the amplitude of the fundamental wave voltage. Therefore, the smaller the value of the peak voltage / fundamental wave amplitude, the closer the fundamental wave voltage amplitude and the peak voltage value are, which means that the fundamental wave voltage can be increased under the constraints of the voltage applied to the coil. In other words, the smaller the value of the peak voltage / fundamental wave amplitude, the easier it is to generate torque under voltage constraints. In Examples 1 to 4, the value of the peak voltage / fundamental wave amplitude is smaller than in Comparative Examples 1 and 2, and it can be said that it is easier to generate torque under voltage constraints than in Comparative Examples 1 and 2. Furthermore, Examples 1 and 2 are slightly superior in torque output to Examples 3 and 4.

[0059] 10 shows simulation results of the back electromotive force in the UV line voltage for Example 1 and Comparative Examples 4 and 5. In Example 1 and Comparative Examples 4 and 5, the number of outer bridges 35a and the number of middle bridges 35b are equal for each magnetic pole 33. Also, the bridges 35 are similarly arranged asymmetrically with respect to the d axis. However, the difference is that the bridges 35 in Example 1 are arranged symmetrically with respect to the q axis, whereas the bridges 35 in Comparative Examples 4 and 5 are arranged asymmetrically with respect to the q axis.

[0060] In Comparative Example 4, the voltage increased and peaked near an electrical angle of 50°, exceeding the maximum amplitude of the fundamental wave voltage near an electrical angle of 60°. Furthermore, the voltage increased and peaked at an electrical angle slightly shifted from 60° and at an electrical angle of 80°. In Comparative Example 5, the voltage increased and peaked near an electrical angle of 72°, exceeding the maximum amplitude of the fundamental wave voltage near 60°. Furthermore, the voltage increased and peaked near an electrical angle of 60° and near an electrical angle of 42°. The voltage waveform of Comparative Example 5 resembled the voltage waveform of Comparative Example 4, inverted around an electrical angle of 60°. This is because the arrangement of the bridges 35 in Comparative Example 5 is equivalent to the arrangement of the bridges 35 in Comparative Example 4 inverted with respect to the d-axis.

[0061] As described above, the arrangement of the bridges 35 in Examples 1 to 4 was more effective in reducing the counter electromotive force than the arrangement of the bridges 35 in Comparative Examples 1 to 5.

[0062] <Qualitative explanation of the effects of the invention> The back electromotive force tends to increase when the d-axis is parallel to the central axis of the teeth 22 and when the d-axis is parallel to the central axis of the slots 21. When the d-axis is parallel to the central axis of the teeth 22, the voltage (referred to as voltage A) at the phase of the maximum fundamental wave value of the back electromotive force (line voltage) increases or decreases. When the d-axis is parallel to the central axis of the slots 21, the voltage (referred to as voltage B) at a position shifted in phase from the maximum fundamental wave value relative to the electrical angle when the rotor 30 rotates from the central axis of the teeth 22 to the central axis of the slots 21 increases or decreases significantly.

[0063] In the case of Comparative Example 2, only the center bridge 35b is arranged, and voltage A becomes large. In the case of Comparative Example 1, only the outer bridge 35a is arranged, and voltage B becomes large. The arrangements of the bridges 35 in Examples 1 to 4 are intermediate structures that use both the outer bridge 35a and the center bridge 35b, and can suppress increases in the peaks of the back electromotive force at voltages A and B.

[0064] 11 shows the back electromotive force waveforms of Comparative Example 1, Comparative Example 2, and Example 1, along with the phases of voltage A and voltage B. Voltage A is the back electromotive force at an electrical angle of 60°, and voltage B is the back electromotive force at electrical angles of 45° and 75°. In Example 1, voltage A and voltage B exhibited values ​​intermediate between those of Comparative Example 1 and Comparative Example 2, and the peak voltage was reduced overall.

[0065] 12 to 14 show the analysis results of the magnetic flux density distribution for Example 1, Comparative Example 1, and Comparative Example 2, respectively. In Fig. 12 to Fig. 14, (a) shows the analysis results of the magnetic flux density distribution at an electrical angle of 45°, and (b) shows the analysis results of the magnetic flux density distribution at an electrical angle of 60°. As shown in Figs. 12 to 14, the teeth 22 are numbered #1 to #12, and the following description will use these numbers.

[0066] <Reason why magnetic flux fluctuations become large in the outer bridge 35a: electrical angle 45°> As shown in FIG. 12(a) , at an electrical angle of 45° in the first embodiment, the outer bridge 35a is located between two teeth 22 (#3 and #4, #7 and #8). At this time, the magnetic flux from the magnet 31 tends to flow directly into the teeth 22 via the outer bridge 35a, which tends to increase the fluctuation of the magnetic flux flowing into the teeth 22. Fluctuations in the magnetic flux are also likely to occur due to the effect of magnetic flux cancellation, where the magnetic flux flowing into the rotor 30 from the two teeth 22 is canceled out by the outer bridge 35a. Furthermore, the center bridge 35b is located farther from the teeth 22 than the outer bridge 35a. Therefore, the magnetic resistance change in the magnetic path when the magnetic flux passes to the teeth 22 via the center bridge 35b is smaller, and magnetic flux fluctuations are less likely to occur compared to the outer bridge 35a. Therefore, the outer bridge 35a tends to increase the back electromotive force around an electrical angle of 45°.

[0067] <Reason why magnetic flux fluctuations increase in the middle bridge 35b: electrical angle 60°> As shown in Figure 12(b) , at an electrical angle of 60° in the first embodiment, magnetic flux flows through the teeth 22 (#12, #10) adjacent to the teeth 22 (#1, #9), which tends to increase magnetic flux fluctuations in the teeth 22 (#1, #9) as the rotor 30 rotates. The outer bridge 35a allows magnetic flux to flow only through the opposing teeth 22 (#3, #7), making magnetic flux fluctuations less likely to occur. Therefore, at an electrical angle of around 60°, the middle bridge 35b tends to increase the back electromotive force.

[0068] As shown in FIG. 13(a), at an electrical angle of 45° in Comparative Example 1, outer bridges 35a are located between the teeth 22 (#1, #2), between the teeth 22 (#3, #4), between the teeth 22 (#7, #8), and between the teeth 22 (#9, #10). Therefore, compared to Example 1, in which the outer bridges 35a are located between the teeth 22 (#3, #4) and between the teeth 22 (#7, #8), the fluctuations in the magnetic flux flowing into the teeth 22 are likely to be even larger. Furthermore, because the center bridge 35b is not provided, magnetic flux fluctuations are unlikely to occur near an electrical angle of 60°. Therefore, in Comparative Example 1, a large back electromotive force is likely to be generated near an electrical angle of 45°.

[0069] As shown in FIG. 14(b), at an electrical angle of 60° in Comparative Example 2, magnetic flux flows through the teeth 22 (#12, #10) adjacent to the teeth 22 (#1, #9) and the teeth 22 (#4, #6) adjacent to the teeth 22 (#3, #7). Therefore, magnetic flux fluctuations associated with the rotation of the rotor 30 tend to be larger than in Example 1, in which magnetic flux flows through the teeth 22 (#12, #10) adjacent to the teeth 22 (#1, #9). Furthermore, because the outer bridge 35a is not provided, magnetic flux fluctuations are less likely to occur near an electrical angle of 45°. Therefore, in Comparative Example 2, a large back electromotive force tends to be generated near an electrical angle of 60°.

[0070] <Reference example: Alternate lamination of rotor core> In Example 1 and Example 2, the arrangement of the bridges 35 at the south magnetic pole 33S and the arrangement of the bridges 35 at the north magnetic pole 33N are interchanged. That is, in Example 1 and Example 2, the structure of the rotor 30 excluding the magnet 31 is the same when rotated by one magnetic pole. Therefore, by stacking the rotor 30 having the bridge 35 arrangement of Example 1 and the rotor 30 having the bridge 35 arrangement of Example 2 along the rotation axis as partial rotors, it is possible to improve the weight balance during rotation of the rotor 30. The same applies to Example 3 and Example 4.

[0071] 10, the arrangement of the bridges 35 in Comparative Examples 4 and 5 alone did not have the effect of suppressing the back electromotive force. However, by stacking them alternately in the axial direction as described below, the effect of reducing the back electromotive force can be obtained.

[0072] The same effect as the structure of bridge 35 in Example 1 can also be achieved by "Structure X: axially alternately stacking the bridge-arranged electromagnetic steel sheets of Comparative Examples 1 and 2, which had significant issues with back electromotive force when used alone," or "Structure Y: axially alternately stacking the bridge-arranged electromagnetic steel sheets of Comparative Examples 4 and 5, which had significant issues with back electromotive force when used alone." Structures X and Y are based on alternate stacking, and the disadvantage is that two types of electromagnetic steel sheets must be prepared to make up rotor 30. Structure Y is mirror-symmetrical with respect to the q axis, and has a shape in which the front and back of the electromagnetic steel sheets are reversed, making it possible to manufacture using the same mold. Therefore, it is believed that Structure Y can reduce production costs compared to Structure X.

[0073] The bridge arrangement of Example 1 can reduce the back electromotive force even without alternately stacking the electromagnetic steel sheets with the bridge arrangement of Example 2. The same is true for Example 3. However, if the bridge arrangement of Example 1 and Example 2 requires alternate stacking of the electromagnetic steel sheets in the axial direction to achieve rotational balance (Structure Z), the difference with Structure Y becomes smaller when considering only the effect of suppressing the back electromotive force. However, Structure Z can stack the punched core by rotating it through an angle equivalent to one magnetic pole, whereas Structure Y requires stacking it upside down, so Structure Z is advantageous in terms of production man-hours. As a reference example, Figure 15 shows the back electromotive force waveforms of Example 1, Structure X, and Structure Y. Both Structure X and Structure Y are able to suppress the back electromotive force in the same way as Example 1.

[0074] It should be noted that the present invention is not limited to the above-described embodiment and its modifications, and various changes and modifications are possible within the scope of the claims of this application. [Explanation of symbols]

[0075] 10 rotating electric machine, 20 stator, 21 slot, 22 teeth, 23 back yoke, 30 rotor, 31 magnet, 32, 32a, 32b flux barrier, 33 magnetic pole, 33N N magnetic pole, 33S S magnetic pole, 34 tip region, 34a first tip region, 34b second tip region, 35 bridge, 35a outer bridge, 35b middle bridge

Claims

1. a stator; a rotor having magnetic poles formed by embedding magnets in a flux barrier; Equipped with the blacks barrier extends along the circumferential direction of the rotor with the d-axis as its center, and has tip regions on both sides thereof that extend toward the outer circumferential surface of the rotor; the magnets are embedded in a portion along the circumferential direction of the rotor, and the tip region is formed as a space in which the magnets are not embedded, Each magnetic pole of a magnetic pole pair adjacent to each other in the circumferential direction of the rotor has a bridge in the tip region, the bridge is one of two types: an outer bridge formed on the outer peripheral surface of the rotor in the tip region, and an intermediate bridge disposed in an intermediate portion of the tip region on the inner diameter side of the outer bridge, The number of the outer bridges and the number of the middle bridges in the magnetic pole pair are the same, A rotating electric machine characterized in that the outer bridges and the middle bridges are arranged symmetrically with respect to one of the d-axis and q-axis and asymmetrically with respect to the other axis.

2. 2. The rotating electric machine according to claim 1, In one of the magnetic poles of the magnetic pole pair, the arrangement of the outer bridge and the middle bridge is asymmetric with respect to the d axis, a rotating electric machine, characterized in that the arrangement of the outer bridge and the middle bridge at the other magnetic pole of the magnetic pole pair is symmetrical with respect to the q axis to the arrangement at the one magnetic pole of the magnetic pole pair.

3. 2. The rotating electric machine according to claim 1, In one of the magnetic poles of the magnetic pole pair, only the outer bridge is arranged symmetrically with respect to the d axis, A rotating electric machine, characterized in that, at the other magnetic pole of the magnetic pole pair, only the center bridge is arranged symmetrically with respect to the d axis.

4. A rotating electric machine according to any one of claims 1 to 3, the rotor has a plurality of the flux barriers in a radial direction, A rotating electric machine characterized in that the arrangement of the outer bridge and the middle bridge is applied to the flux barrier arranged on the inner, outermost radial side of the flux barrier.

5. A rotating electric machine according to any one of claims 1 to 3, The stator has a plurality of teeth arranged at equal intervals in the circumferential direction, When the open angle between the adjacent teeth is α and the angle formed by a line connecting the center of the rotation axis and the center of the circumferential direction of the two bridges sandwiching the d axis at the magnetic pole is β, α×N≦β≦α×(N+1), where N is an integer of 1 or more. A rotating electric machine characterized by satisfying the following:

6. A rotating electric machine according to any one of claims 1 to 3, The rotor is a rotating electric machine characterized in that it is formed by stacking partial rotors in the direction of the rotation axis, with the positions of the outer bridges and the middle bridges interchanged with each other.

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