Rotary electric machine
The rotating electric machine's innovative coil material selection reduces weight and maintains performance by using a high-resistivity, low-density second coil, enhancing efficiency in both high torque and high rotation operations.
Patent Information
- Application Number
- JP2024010874
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-01-29
- Publication Date
- 2025-08-08
AI Technical Summary
Rotating electric machines with winding switching functions face an increase in weight due to the inclusion of a switching switch, necessitating a reduction in weight while maintaining performance.
A rotating electric machine design featuring a first coil and a second coil made of different materials, where the second coil has higher electrical resistivity and lower weight density, allowing for weight reduction without compromising performance.
The design achieves a reduction in weight and power consumption while maintaining efficiency across varying operational ranges, particularly in high torque and high rotation conditions.
Smart Images
Figure 2025116448000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a rotating electric machine having a winding switching function. [Background technology]
[0002] Conventionally, rotating electric machines have been known that have a winding switching function that allows the number of winding turns to be changed depending on the operating range, with the aim of increasing torque in the low rotation range or increasing output in the high rotation range (see, for example, non-patent document 1). [Prior art documents] [Patent documents]
[0003] [Non-Patent Document 1] Takayuki Sato, Masakatsu Shintomi, Nobuhide Seo: "Development of Electronic Winding Switching Motor Drive for Demio EV," Mazda Technical Review No. 30 (2012) Summary of the Invention [Problem to be solved by the invention]
[0004] In rotating electric machines with this type of winding switching function, the weight of the rotating electric machine increases due to the provision of a switching switch, so there is a demand for reducing the weight of the rotating electric machine while suppressing a decrease in performance.
[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a rotating electric machine having a winding switching function that can reduce weight while suppressing performance degradation. [Means for solving the problem]
[0006] A rotating electric machine according to one aspect includes a rotor, a stator around which a first coil and a second coil are wound for each phase, and a changeover switch that switches the connection between the first coil and the second coil between a first mode in which the first coil is energized and a second mode in which the first coil and the second coil are connected in series. The second coil is made of a material that has a higher electrical resistivity and a lower weight density than the first coil.
[0007] In the above embodiment, the stator may have a plurality of teeth in the circumferential direction, and the first coil and the second coil may be wound around the same teeth. Also, the rotor may be disposed on the inner circumferential side of the stator, and the second coil may be wound more inward than the first coil.
[0008] In the above aspect, the stator may have a plurality of teeth in the circumferential direction, and the first coil and the second coil may be wound around different teeth.
[0009] In one embodiment of the above, the material of the first coil may be copper, and the material of the second coil may be aluminum. [Effects of the Invention]
[0010] According to one aspect, it is possible to provide a rotating electric machine having a winding switching function that can reduce weight while suppressing performance degradation. [Brief explanation of the drawings]
[0011] [Figure 1] 1 is a schematic diagram showing a first configuration example of a rotating electric machine according to an embodiment of the present invention; [Figure 2] FIG. 4 is a schematic diagram showing a second configuration example of the rotating electric machine according to the present embodiment. [Figure 3] 10 is a diagram showing the circuit configuration of U-phase, V-phase, and W-phase coils in a first configuration example and a second configuration example. FIG. [Figure 4] 4 is a diagram illustrating an example of the operation of the U-phase circuit illustrated in FIG. 3. [Figure 5] 4A and 4B are diagrams showing examples of combinations of materials for the first coil and the second coil in this embodiment. [Figure 6] FIG. 10 is a diagram showing analysis results in an example. [Figure 7] FIG. 10 is a diagram showing analysis results in an example. DETAILED DESCRIPTION OF THE INVENTION
[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiments, in order to make the explanation easier to understand, the structures and elements other than the main parts of the present invention will be explained in a simplified or omitted manner. Furthermore, the same elements will be given the same reference numerals in the drawings. Note that the shapes, dimensions, etc. of the elements shown in the drawings are shown schematically and do not represent the actual shapes, dimensions, etc.
[0013] In addition, in the following description, the direction parallel to the extension direction of the rotation axis Ax of the rotating electric machine will be referred to as the axial direction, the circumferential direction centered on the rotation axis Ax will be simply referred to as the circumferential direction, and the radial direction centered on the rotation axis Ax will be simply referred to as the radial direction.
[0014] The rotating electric machine 1 of this embodiment is, for example, an inner rotor type motor for an electric vehicle, and has a winding switching function that enables the number of turns of the coil winding to be switched, as shown in the first and second configuration examples below.
[0015] Fig. 1 is a schematic diagram showing a first configuration example of a rotating electric machine 1 according to the present embodiment. Fig. 1(A) is a front view of the rotating electric machine 1 of the first configuration example, and Fig. 1(B) is a cross-sectional view taken along line II' in Fig. 1(A).
[0016] The rotating electric machine 1 of the first configuration example shown in FIG. 1 is a three-phase AC motor with four poles and six slots, and includes a rotor 2, a shaft 3, a stator 4, coils 5a and 5b, and a changeover switch 6.
[0017] The rotor 2 may be any of a magnet-embedded rotor, a surface magnet rotor, a squirrel-cage rotor, a wound rotor, etc. In Fig. 1, an example of the rotor 2 is an magnet-embedded rotor.
[0018] The rotor 2 has a cylindrical core made, for example, of stamped silicon steel plates laminated in the axial direction. A shaft 3 is fitted into the core of the rotor 2 along the rotation axis Ax, and the rotor 2 is rotatably supported by a bearing (not shown) centered on the shaft 3. A plurality of permanent magnets 2a are embedded in the rotor 2 in the circumferential direction, forming a predetermined number of magnetic poles. The permanent magnets 2a are arranged so that adjacent magnetic poles in the circumferential direction of the rotor 2 have opposite polarities.
[0019] The stator 4 is disposed on the outer periphery of the rotor 2 across an air gap. In the rotating electric machine 1, the magnetic field of the stator 4 is switched in sequence by controlling the current in coils 5a and 5b (described later), causing the rotor 2 and the shaft 3 to rotate around the rotation axis Ax due to the attractive or repulsive force with the magnetic field of the rotor 2.
[0020] The stator 4 is a cylindrical member with a central space, and houses the rotor 2 in the central space centered on the rotation axis Ax. On the inner periphery of the stator 4, multiple teeth 4a are arranged at equal intervals in the circumferential direction, each protruding radially inward toward the rotation axis Ax. Slots 4b are formed between adjacent teeth 4a of the stator 4. The stator 4 of the first configuration example has six teeth 4a and six slots 4b.
[0021] U-phase, V-phase, and W-phase coils 5a, 5b are wound around the teeth 4a of the stator 4 with a phase shift in the circumferential direction. Also, as shown in Fig. 1(B), a changeover switch 6 is disposed on one axial side of the stator 4 to switch the connection state of the coils 5a, 5b.
[0022] In this embodiment, the coils wound around the stator 4 include a first coil 5a that is energized in both the high torque region and the high rotation region, and a second coil 5b that is energized in the high torque region. In the first configuration example, the first coil 5a and the second coil 5b of the same phase are wound around each tooth 4a. In each tooth 4a in the first configuration example, the first coils 5a are wound more inwardly than the second coils 5b. In the following description, the first coil 5a or the wiring on the first coil 5a side may be referred to as A, and the second coil 5b or the wiring on the second coil 5b side may be referred to as B.
[0023] 2 is a schematic diagram showing a second configuration example of the rotating electric machine 1 in this embodiment. Fig. 2(A) is a front view of the rotating electric machine 1 of the second configuration example, and Fig. 2(B) is a cross-sectional view taken along line II-Ax-II' in Fig. 2(A). In the following description of the second configuration example, elements common to the first configuration example described above are given the same reference numerals, and redundant description will be omitted where appropriate.
[0024] 2 is a three-phase AC motor with 10 poles and 12 slots, and like the first configuration example, includes a rotor 2, a shaft 3, a stator 4, coils 5a and 5b, and a changeover switch 6. The rotor 2 in the second configuration example has the same configuration as the first configuration example, except for the number of poles.
[0025] The stator 4 of the second configuration example has 12 teeth 4a and 12 slots 4b, and U-phase, V-phase, and W-phase coils 5a, 5b are wound around the teeth 4a with their phases shifted in the circumferential direction. In the second configuration example, as shown in Fig. 2(A), the first coil 5a and the second coil 5b of the same phase are wound separately around adjacent teeth 4a. Also, as shown in Fig. 2(B), a changeover switch 6 for switching the connection state of the coils 5a, 5b is disposed on one axial side of the stator 4.
[0026] Fig. 3 is a diagram showing the circuit configuration of the U-phase, V-phase, and W-phase coils 5a, 5b in the first and second configuration examples. Fig. 3 shows one side of the U-phase, V-phase, and W-phase coils 5a, 5b connected in parallel, and the circuit configuration of the other side is common to the one side and is therefore not shown.
[0027] In the circuit shown in Fig. 3, the U, V, and W phases are star-connected. Each of these phases is provided with a first coil 5a, a second coil 5b, and two switches SW1 and SW2 that function as changeover switches 6. Since the U, V, and W phases in Fig. 3 all have the same circuit configuration, the following description will focus on the U phase circuit (left side of Fig. 3), and redundant descriptions of the V and W phase circuits will be omitted.
[0028] One end of the first coil 5a receives a U-phase AC voltage from an inverter (not shown). The other end of the first coil 5a branches into two, one connected to one end of SW1 and the other connected to one end of SW2. One end of the second coil 5b is connected to the other end of SW1. The other end of the second coil 5b is connected to the neutral point N. Meanwhile, the other end of SW2 is connected to the neutral point N, bypassing the second coil 5b.
[0029] Figure 4 is a diagram showing an example of the operation of the U-phase circuit shown in Figure 3. Figure 4(A) shows the state of the U-phase circuit when the rotating electric machine 1 operates in a high torque region, and Figure 4(B) shows the state of the U-phase circuit when the rotating electric machine 1 operates in a high rotation region. The operation of the V-phase and W-phase circuits is similar to that of the U-phase.
[0030] In the high torque region shown in FIG. 4A, SW1 is turned on while SW2 is turned off. During operation in the high torque region, the first coil 5a and the second coil 5b are connected in series to the U-phase power supply line. In this way, during operation in the high torque region, both the first coil 5a and the second coil 5b are excited, and all windings of the stator 4 are used, allowing the rotating electric machine 1 to generate high torque. Note that operation in the high torque region is an example of the second mode.
[0031] Also, in the high rotation range shown in FIG. 4(B), SW1 is turned off while SW2 is turned on. During operation in the high rotation range, only the first coil 5a is connected to the U-phase power supply line, and the second coil 5b is not energized. In other words, during operation in the high rotation range, only the first coil 5a is excited, and the number of energized windings in the stator 4 is reduced compared to operation in the high torque range. Therefore, during operation in the high rotation range, the induced voltage with the rotor 2 is reduced compared to operation in the high torque range, and the high rotation characteristics of the rotating electric machine 1 are improved. Note that operation in the high rotation range is an example of the first mode.
[0032] In the rotating electric machine 1 of this embodiment, the first coil 5a and the second coil 5b are made of different materials. Specifically, the second coil 5b, which is used only in the high torque region, is made of a material with higher electrical resistivity and lower weight density than the first coil 5a, which is used in the high torque region and high rotation region.
[0033] Fig. 5 shows an example of a combination of materials for the first coil 5a and the second coil 5b in this embodiment. Note that the material combinations in Fig. 5 are merely examples, and are not necessarily limited to the following configuration.
[0034] FIG. 5(A) shows the case where the material of the first coil 5a is copper (A, electrical resistivity: 1.68×10 -8 Ω m, weight density: 8.96 g cm -3 ), and the material of the second coil 5b is aluminum (B, electrical resistivity: 2.65 × 10 -8 Ω m, weight density: 2.70g cm -3 5(A) shows an example in which the ratio of the electrical resistivity of the second coil 5b to the first coil 5a (electrical resistivity B / A) is 158%, and the ratio of the weight density of the second coil 5b to the first coil 5a (weight density B / A) is 30%.
[0035] FIG. 5B shows the case where the material of the first coil 5a is silver (A, electrical resistivity: 1.59×10 -8 Ω m, weight density: 10.49g cm -3 ), and the material of the second coil 5b is copper (B, electrical resistivity: 1.68 × 10-8 Ω m, weight density: 8.96 g cm -3 5(B) shows an example in which the ratio of the electrical resistivity of the second coil 5b to the first coil 5a (electrical resistivity B / A) is 106%, and the ratio of the weight density of the second coil 5b to the first coil 5a (weight density B / A) is 85%.
[0036] FIG. 5C shows the case where the material of the first coil 5a is copper (A, electrical resistivity: 1.68×10 -8 Ω m, weight density: 8.96 g cm -3 ), and the material of the second coil 5b is a composite material of carbon nanotubes and copper (B_ electrical resistivity: 2.13 × 10 -8 Ω m, weight density: 5.50g cm -3 5(C) shows an example in which the ratio of the electrical resistivity of the second coil 5b to the first coil 5a (electrical resistivity B / A) is 127%, and the ratio of the weight density of the second coil 5b to the first coil 5a (weight density B / A) is 61%.
[0037] As described above, according to the configuration of this embodiment, the weight density of the second coil 5b, which is a part of the coils of the stator 4, is reduced. Therefore, the weight of the rotating electric machine 1 can be reduced and the power consumption can be improved compared to when the first coil 5a and the second coil 5b are formed from the same material. As a result, the rotating electric machine 1 of this embodiment can also reduce the increase in weight of the selector switch 6.
[0038] Furthermore, in the configuration of this embodiment, the second coil 5b, which is used only in the high torque region, is made of a material with a higher electrical resistivity and a lower weight density than the first coil 5a, which is used in the high torque region and the high rotational speed region. In other words, in the rotating electric machine 1 of this embodiment, the second coil 5b, which has a high electrical resistivity, is not used in the high rotational speed region where only one coil is energized. Therefore, with the configuration of this embodiment, it is possible to reduce the weight of the rotating electric machine 1 while suppressing a decrease in efficiency on the high rotational speed side, which has a large contribution to modal efficiency in electric vehicle applications.
[0039] Furthermore, in this embodiment, if copper is used as the material for the first coil 5a and aluminum is used as the material for the second coil 5b, it is advantageous in that material costs can be reduced compared to when all coils are made of copper.
[0040] In addition, in each tooth 4a in the first configuration example of the present embodiment, the first coil 5a is wound more inward than the second coil 5b. With this configuration, it is possible to reduce AC copper loss compared to when the second coil 5b is wound more inward than the first coil 5a.
[0041] (Example) In the example, a motor having a winding switching function was compared to see how the weight of magnetic circuit components and the difference in motor efficiency change depending on the material of the first coil and the second coil.
[0042] In the examples, the differences in magnetic circuit component weight and motor efficiency were calculated by numerical analysis for the following cases: (1) when both the first coil and the second coil are made of copper; (2) when the first coil is made of copper and the second coil is made of aluminum; and (3) when both the first coil and the second coil are made of aluminum.
[0043] Fig. 6 shows the analysis results of the example. The axis and bar graph on the left side of Fig. 6 indicate the magnetic circuit component weight [pu]. The axis and line graph on the right side of Fig. 6 indicate the WLTC (Worldwide harmonized Light vehicle Test Cycles) mode motor efficiency difference [%]. Furthermore, the numerical values (2) and (3) in Example 1 indicate values normalized based on the analysis result of (1).
[0044] In the examples, when the weight of the magnetic circuit components in (1) is set to 1, the weight of the magnetic circuit components in (2) is 0.92, and the weight of the magnetic circuit components in (3) is 0.84. In other words, the weight of the magnetic circuit components is reduced by changing the coil winding from copper to aluminum in the case of (1).
[0045] On the other hand, in the example, when the motor efficiency difference in (1) was set to 0%, the motor efficiency difference in (2) was -0.2%, and the motor efficiency difference in (3) was -0.7%.
[0046] As shown in Figure 6, when comparing Examples (1) to (3), the slope of the line segment representing the difference in motor efficiency between (2) and (3) is more negative than the slope of the line segment representing the difference in motor efficiency between (1) and (2). In other words, when only the second coil is made of aluminum as in (2), compared to when both coils are made of aluminum as in (3), it is possible to reduce the weight of the magnetic circuit components without significantly reducing motor efficiency in WLTC mode compared to (1).
[0047] FIG. 7 is a graph showing the relationship between torque and rotation speed in the high torque region and the high rotation speed region in Example (2). The vertical axis of FIG. 7 represents torque [Nm], and the horizontal axis of FIG. 7 represents rotation speed [rpm]. FIG. 7 also shows the distribution of the operating points of the WLTC mode applied in the numerical analysis, mapped to the operating points. The motor efficiency difference in FIG. 6 (2) is calculated based on the distribution of the operating points shown in FIG. 7.
[0048] As shown in Fig. 7, when operating in the high torque region indicated by the solid line in the figure, higher torque can be obtained at lower rotation speeds compared to operation in the high rotation speed region, but the torque drops and cannot be maintained at higher rotation speeds. On the other hand, when operating in the high rotation speed region indicated by the dashed line in the figure, stable torque can be obtained even at higher rotation speeds compared to operation in the high torque region. It can be seen that by setting the switching rotation speed at the intersection of the graphs for the high torque region and the high rotation speed region, a motor that can be used in both the high torque region and the high rotation speed region can be achieved.
[0049] The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.
[0050] For example, in the above embodiment, the rotating electric machine is a motor, but the rotating electric machine may be a generator. Furthermore, the rotating electric machine of the above embodiment is not limited to use in an electric vehicle, and may be used in other applications.
[0051] The number of poles and the number of slots in the motors of the first and second configuration examples of the above embodiment can be changed as appropriate. Also, in the first configuration example of the above embodiment, the second coil 5b may be wound more inward than the first coil 5a.
[0052] Furthermore, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]
[0053] REFERENCE SIGNS LIST 1... rotating electric machine, 2... rotor, 3... shaft, 4... stator, 5a... first coil, 5b... second coil, 6... changeover switch
Claims
1. A rotor; a stator around which a first coil and a second coil are wound for each phase; a changeover switch that switches the connection between the first coil and the second coil between a first mode in which the first coil is energized and a second mode in which the first coil and the second coil are connected in series, The second coil is formed of a material having a higher electrical resistivity and a lower weight density than the first coil. Rotating electric motor.
2. the stator has a plurality of teeth in a circumferential direction, The first coil and the second coil are wound around the same teeth. The rotating electric machine according to claim 1 .
3. the rotor is disposed on the inner circumferential side of the stator, The first coil is wound more inwardly than the second coil. The rotating electric machine according to claim 2 .
4. the stator has a plurality of teeth in a circumferential direction, The first coil and the second coil are wound around different teeth. The rotating electric machine according to claim 1 .
5. the material of the first coil is copper; The material of the second coil is aluminum. The rotating electric machine according to any one of claims 1 to 4.