Variable magnetic flux rotating electric machine

Abstract

To provide a variable magnetic flux rotary electric machine in which a rotor core can be formed into a simple shape and the magnetic characteristic of a variable magnetic flux region or the like can be easily set.SOLUTION: A variable magnetic flux rotary electric machine 1 includes a rotor 3, and a stator 2 that generates a rotation magnetic field with respect to the rotor 3. The rotor 3 includes a rotor core 4 formed of a soft magnetic material, and a plurality of permanent magnets 5 that are embedded along the circumferential direction of the rotor core 4 such that the different polarities are arranged alternately. A core absence region 7 where the rotor core 4 is absent is disposed between the adjacent permanent magnets 5. A magnetic member 6 having a lower magnetic permeability than the rotor core 4 and having a lower saturated magnetic flux density than the rotor core 4 is disposed in the core absence region 7.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a variable magnetic flux rotating electric machine that includes a rotor and a stator that generates a rotating magnetic field relative to the rotor, and has a plurality of permanent magnets embedded inside the rotor core so as to be aligned circumferentially. [Background technology]

[0002] Patent Document 1 describes a variable magnetic flux rotating electric machine in which a magnetic flux bypass path is formed in the rotor of an interior permanent magnet synchronous motor. Fig. 20 shows a configuration diagram of this variable magnetic flux rotating electric machine as seen from a cross section perpendicular to the rotational axis direction. The variable magnetic flux rotating electric machine 201 shown in the figure includes a circular stator 211, a rotor 212 that is concentric with the stator 211 and arranged so as to have an air gap between it and the stator 211, and a plurality of permanent magnets 213 fitted into the rotor 212. A stator winding 220 is wound around teeth 221 of the stator 211.

[0003] The rotor 212 has a rotor core 231. The rotor core 231 is cylindrical and has a laminated steel plate structure, which is made by laminating electromagnetic steel plates in the direction of the rotation axis. Near the periphery of the rotor core 231, a plurality of permanent magnets 213 are provided along the circumferential direction at equal intervals, with adjacent permanent magnets 213 having opposite polarities.

[0004] Rotor 212 has magnetic barriers (flux barriers) 234, 235, which are spaces formed by stamping the electromagnetic steel sheet that forms rotor core 231, between the magnetic poles formed by adjacent permanent magnets 213. As shown in the figure, magnetic barrier 234 is formed in a substantially triangular shape. Magnetic barrier 235 is formed in a substantially U-shape, closer to the rotation center than magnetic barrier 234, so as to cover magnetic barrier 234.

[0005] The magnetic barriers 234, 235 have a higher magnetic resistance than the magnetic steel sheets, and therefore act as magnetic flux barriers against the magnetic flux of the magnets. Therefore, a magnetic flux bypass path 236 is formed between the magnetic barriers 234 and 235, which serves as a path for the magnetic flux emitted from the permanent magnet 213 to leak to the magnetic pole side formed by the adjacent permanent magnet 213.

[0006] When no current is applied to the stator winding 220 of the stator 211, a portion of the magnetic flux from the permanent magnet 213 leaks to the adjacent opposite pole through the magnetic flux bypass path 236. This relatively reduces the amount of magnetic flux of the main magnetic flux component from the permanent magnet 213 toward the stator 211, i.e., the stator flux linkage, and the magnetic force of the permanent magnet 213 appears weaker. In other words, when the current applied to the stator winding 220 is small, such as under no load or low load, leakage magnetic flux is generated that flows through the magnetic flux bypass path 236. This reduces the back electromotive force generated by the magnetic flux from the permanent magnet 213 and the torque generated in the rotor 212. This also reduces iron loss caused by the stator flux linkage. This effect is particularly effective in improving the efficiency of a rotating electric machine under low load and high speed conditions.

[0007] On the other hand, if the current flowing through the stator winding 220 is increased, the magnetic flux bypass path 236 becomes magnetically saturated, reducing the leakage magnetic flux and relatively increasing the main magnetic flux component linking to the stator side, thereby increasing the torque.

[0008] In this way, the variable magnetic flux type rotating electric machine 201 can change the magnetic path of a portion of the magnetic flux (leakage magnetic flux) emanating from the permanent magnets 213 of the rotor 212 by the action of the load current (stator current) applied to the stator winding 220. Due to this feature, the rotating electric machine 201 can change the stator flux linkage by controlling the stator current, and therefore the magnetic force of the permanent magnets 213 of the rotor 212 can be made apparently variable by current control. Due to these characteristics, the rotating electric machine 201 is called a "variable magnetic flux type" rotating electric machine, and is also called a variable leakage magnetic flux motor. Furthermore, the control that makes the magnetic force of the permanent magnets 213 apparently variable by controlling the stator current is called variable magnetic flux control or field-weakening control. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2017-17783 Summary of the Invention [Problem to be solved by the invention]

[0010] The variable magnetic flux rotating electric machine described in Patent Document 1 has a complex shape in which two types of magnetic barriers are formed between adjacent permanent magnets in the rotor core, and therefore there is a need to realize a variable magnetic flux rotating electric machine with a simpler shape. Also, although the characteristics of the rotating electric machine, such as variable range characteristics, torque characteristics, magnetic characteristics, and mechanical characteristics, can be set depending on the structure of the two types of magnetic barriers, there is a need to realize a variable magnetic flux rotating electric machine in which the characteristics can be set more easily.

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide a variable magnetic flux type rotating electric machine in which the rotor core can be made into a simple shape and the characteristics of the rotating electric machine can be easily set. [Means for solving the problem]

[0012] The variable magnetic flux rotating electric machine according to claim 1 is a variable magnetic flux rotating electric machine including a rotor and a stator that generates a rotating magnetic field for the rotor, wherein the rotor has a rotor core made of a soft magnetic material and a plurality of permanent magnets embedded inside the rotor core so that the polarities are alternately changed along the circumferential direction of the rotor core, and a coreless region where the rotor core is absent is provided between adjacent permanent magnets, and a magnetic member having a lower magnetic permeability and a lower saturation magnetic flux density than the rotor core is disposed in the coreless region. The magnetic member is a magnetic composite material in which magnetic powder, which is a powdered soft magnetic material, is mixed with resin, the coreless region is entirely surrounded by the rotor core, the magnetic member is disposed throughout the coreless region, the magnetic member can be magnetically saturated by applying the rotating magnetic field to rotate the rotor, when the rotating magnetic field is weak and the magnetic member is not magnetically saturated, part of the magnetic flux emitted from the permanent magnet becomes leakage flux that passes through the magnetic member and leaks to the adjacent permanent magnet, and the magnetic flux linking to the stator side is relatively reduced, and when the rotating magnetic field of a strength that causes magnetic saturation is applied to the magnetic member, the magnetic flux emitted from the permanent magnet does not pass through the magnetic member, and the magnetic flux linking to the stator side is relatively increased It is characterized by:

[0013] The variable magnetic flux rotating electric machine according to claim 2 is the one according to claim 1, The relative permeability of the magnetic member is 5 or more and 100 or less, and the saturation magnetic flux density of the magnetic member is 0.2 T or more and 0.8 T or less. It is characterized by the following.

[0015] Claim 3 The variable magnetic flux rotating electric machine according to claim 1 or 2 The present invention is characterized in that the core-free region is provided with a plurality of types of magnetic members having different properties, such as magnetic permeability and saturation magnetic flux density.

[0017] Claim 4 The variable magnetic flux rotating electric machine according to claim Any of 1 to 3 The magnetic powder is at least one of sendust, amorphous iron, and permalloy.

[0018] Claim 5 The variable magnetic flux rotating electric machine according to the present invention is 4 The rotor according to any one of the above, characterized in that the cross-sectional shape of the core-free region in a cross section perpendicular to the rotation axis direction of the rotor is a shape formed by curves without corners.

[0019] Claim 6 The variable magnetic flux rotating electric machine according to the present invention is 5The rotor core according to any one of the above, characterized in that the cross-sectional shape of the core-free region in a cross section perpendicular to the rotation axis direction of the rotor has a curve that bulges out toward the outer periphery of the rotor core. [Effects of the Invention]

[0020] A variable magnetic flux rotating electric machine to which the present invention is applied can have a simple shape because it only requires forming one coreless region between adjacent permanent magnets in the rotor core. Furthermore, the characteristics of the rotating electric machine can be set by changing the characteristics and shape of the magnetic material placed in the coreless region.

[0021] When magnetic members are arranged over the entire coreless region, the region of the magnetic members that serves as a magnetic flux bypass path for leakage magnetic flux can be increased, making it easier to set the characteristics of the rotating electric machine.

[0022] If the core-free region is provided with at least one of a gap and a non-magnetic material in addition to a magnetic material, it is easy to change the proportion of the magnetic material region, making it easy to set the characteristics of the rotating electric machine.

[0023] When a plurality of types of magnetic members having different properties, such as magnetic permeability and saturation magnetic flux density, are provided in the core-free region, it becomes easier to set the characteristics of the rotating electric machine.

[0024] When the magnetic member is a magnetic composite material in which magnetic powder is mixed with resin, the magnetic properties, mechanical strength, etc. can be easily adjusted by changing the types and compounding ratios of the magnetic powder and resin.

[0025] When the magnetic powder is at least one of sendust, amorphous iron, and permalloy, the material has high magnetic permeability and low core loss, and therefore the efficiency of the rotating electrical machine can be increased.

[0026] If the cross-sectional shape of the coreless region in a cross section perpendicular to the rotor's rotational axis direction is a shape composed of curves without corners, stress due to centrifugal force is less likely to be applied, thereby further improving mechanical strength.

[0027] If the cross-sectional shape of the core-free region in a cross section perpendicular to the rotor's rotational axis has a curve that bulges toward the outer periphery of the rotor core, stress due to centrifugal force is less likely to be applied, thereby further improving mechanical strength. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a partial configuration diagram of a variable magnetic flux rotating electric machine to which the present invention is applied, as viewed from a plane perpendicular to the direction of the rotation axis; [Figure 2] 1A to 1C are schematic diagrams for explaining a method for manufacturing a magnetic composite material used in a variable magnetic flux rotating electric machine to which the present invention is applied. [Figure 3] FIG. 2 is a diagram showing a part of FIG. 1, and is a schematic diagram for explaining the operation of the variable magnetic flux rotating electric machine. [Figure 4] 1 is a partial configuration diagram of a variable magnetic flux rotating electric machine to which the present invention is applied, as viewed from a plane perpendicular to the direction of the rotation axis; [Figure 5] 1 is a graph showing a magnetic hysteresis curve of a magnetic composite material. [Figure 6] 1 is a graph showing iron loss of a magnetic composite material. [Figure 7] FIG. 10 is a diagram showing a magnetic flux density distribution of a comparative example obtained by electromagnetic field analysis. [Figure 8] FIG. 4 is a diagram showing the magnetic flux density distribution of Example 1 obtained by electromagnetic field analysis. [Figure 9] FIG. 10 is a diagram showing the magnetic flux density distribution of Example 2 obtained by electromagnetic field analysis. [Figure 10] 1 is a graph showing ideal torque characteristics of a variable magnetic flux rotating electric machine. [Figure 11] 10 is a graph showing torque characteristics of motors with currents of 0 to 40 A obtained by electromagnetic field analysis. [Figure 12]12 is a graph showing an enlarged view of the current range of 5 to 15 A in FIG. 11. [Figure 13] 12 is a graph showing an enlarged view of the current range of 30 to 40 A in FIG. 11. [Figure 14] FIG. 10 is a diagram showing an efficiency map of a motor of a comparative example obtained by electromagnetic field analysis. [Figure 15] FIG. 4 is a diagram showing an efficiency map of the motor according to the first embodiment obtained by electromagnetic field analysis. [Figure 16] FIG. 10 is a diagram showing an efficiency map of the motor according to the second embodiment obtained by electromagnetic field analysis. [Figure 17] FIG. 10 is a diagram showing stress distributions in Example 1 and Comparative Example by electromagnetic field analysis. [Figure 18] 10 is a graph showing torque characteristics with respect to the stator current phase in the first embodiment obtained by electromagnetic field analysis. [Figure 19] 10 is a graph showing torque characteristics with respect to the stator current phase in Example 2 obtained by electromagnetic field analysis. [Figure 20] 1 is a partial configuration diagram of a conventional variable magnetic flux rotating electric machine as viewed from a cross section perpendicular to the rotation axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the embodiments for carrying out the invention will be described in detail, but the scope of the present invention is not limited to these embodiments.

[0030] [First embodiment] Fig. 1 shows a partial cross-section of a variable magnetic flux rotating electric machine 1 to which the present invention is applied, taken along a plane perpendicular to the direction of the rotation axis. Although only a portion of the configuration is shown in the figure, the entire machine is formed in such a manner that such a configuration is continuously repeated to form a ring. The variable magnetic flux rotating electric machine 1 is an electric motor or a generator.

[0031] The variable magnetic flux rotating electric machine 1 includes a rotor 3 and a stator 2 that generates a rotating magnetic field relative to the rotor 3. The rotor 3 has a rotor core 4 made of a soft magnetic material and a plurality of permanent magnets 5 embedded inside the rotor core 4 so that they are arranged with alternating polarities along the circumferential direction of the rotor core 4. Coreless regions 7 where there is no rotor core 4 are provided between adjacent permanent magnets 5, and a magnetic member 6 that has a lower magnetic permeability and a lower saturation magnetic flux density than the rotor core 4 is disposed in the coreless regions 7. This will be explained in detail below.

[0032] The stator 2 is formed in an annular shape. The stator 2 is formed from a ring-shaped stator core 21, a plurality of teeth 22 protruding from the stator core 21 toward the inner periphery, and slots 23 which are spaces between adjacent teeth 22. A stator winding 25 is wound around the teeth 22. A specific illustration of the stator winding 25 is omitted. The stator core 21 is formed from a soft magnetic material (soft magnetic body), such as an electromagnetic steel plate.

[0033] The rotor 3 is concentric with the stator 2 and is arranged so as to have an air gap 11 between it and the stator 2. The rotor 3 has a rotor core 4. The rotor core 4 is made of a soft magnetic material and is formed into a cylindrical shape. As an example, the rotor core 4 is formed into a cylindrical shape using a so-called laminated steel plate structure, which is made by laminating a number of electromagnetic steel plates formed by punching a metal steel plate with high magnetic permeability into an annular shape in the axial direction.

[0034] Inside the rotor core 4, a plurality of permanent magnets 5 are arranged along the circumferential direction near the peripheral portion facing the stator 2, at equal intervals with the polarities of adjacent permanent magnets 5 being opposite to each other. In this embodiment, as an example, the rotor core 4 of the variable magnetic flux rotating electric machine 1 has a six-pole structure in which six permanent magnets are arranged along the circumferential direction.

[0035] The permanent magnets 5 are fitted into gaps formed in corresponding portions of the rotor core 4 and fixed inside the rotor core 4. The magnetization direction of the permanent magnets 5 is the radial direction of the rotor 3, as shown by the "S" and "N" poles in the figure.

[0036] Inside the rotor core 4, a coreless region 7 is formed between each magnetic pole formed by adjacent permanent magnets 5, which is a space formed within the rotor core 4. As an example, the coreless region 7 is formed by stamping the rotor core 4. By forming the coreless region 7 in the rotor core 4, a thin core wall 12, which is a thin wall of the rotor core 4, is formed outside the coreless region 7.

[0037] A magnetic member 6 having a lower magnetic permeability and a lower saturation magnetic flux density than the rotor core 4 is fitted into and fixed to the coreless region 7. In this embodiment, an example is shown in which the magnetic member 6 is arranged without gaps throughout the coreless region 7. In other words, the magnetic member 6 formed with a cross-sectional shape similar to the cross-sectional shape of the coreless region 7 is arranged in the coreless region 7.

[0038] When the rotor core 4 is made of electromagnetic steel, the relative permeability is often several thousand or more. There are no restrictions on the relative permeability of the magnetic member 6 as long as it is smaller than that of the rotor core 4, but it is desirable that it be sufficiently small. As an example, the relative permeability is desirably 5 or more and 100 or less, and more desirably 10 or more and 50 or less.

[0039] When the rotor core 4 is made of electromagnetic steel, the saturation magnetic flux density is often 1 T or more. There are no restrictions on the saturation magnetic flux density of the magnetic member 6, as long as it is smaller than that of the rotor core 4. The saturation magnetic flux density of the magnetic member 6 has a significant effect on the variable magnetic flux characteristics, so it is desirable that it be sufficiently small. As an example, the saturation magnetic flux density is desirably 0.2 T or more and 0.8 T or less, and more desirably 0.3 T or more and 0.7 T or less.

[0040] The magnetic member 6 is not limited to any particular type as long as its characteristics meet the requirements, but is preferably a magnetic composite material in which magnetic powder is mixed with resin. By changing the types and compounding ratios of the magnetic powder and resin used, it is possible to adjust the magnetic characteristics and mechanical strength. By changing the magnetic characteristics, it is possible to change the characteristics of the rotating electric machine.

[0041] The magnetic powder is a soft magnetic material formed into a powder (fine particles). Examples of the material of the magnetic powder include sendust, iron-based amorphous, and permalloy. A material with high magnetic permeability and low iron loss is preferably used as the magnetic powder. In particular, sendust, which has high magnetic permeability and low iron loss, is preferably used. Multiple types of magnetic powder may be blended. The magnetic powder may be insulating coated.

[0042] Although there is no limitation on the size of the magnetic powder, smaller sizes are preferable because they reduce iron loss. As an example, the preferred size of the magnetic powder is a maximum particle size of 20 μm or more and 70 μm or less.

[0043] There are no limitations on the resin material, and for example, thermosetting resin or thermoplastic resin can be used. Examples of thermosetting resins include epoxy resin, phenolic resin, melamine resin, and silicone resin. Epoxy resin is preferably used because of its high dimensional stability, water resistance, chemical resistance, and electrical insulation. Examples of thermoplastic resins include acrylic resin, polytetrafluoroethylene, polyamide, polyacetal, ABS resin, and AS resin.

[0044] There are no limitations on the compounding ratio of magnetic powder to resin, and it can be determined appropriately depending on the desired characteristics. By changing the compounding ratio within the range that can be filled into the resin, the saturation magnetic flux density and magnetic permeability can be changed. As an example, the compounding ratio of magnetic powder is 10% by volume or more and 70% by volume or less.

[0045] An example of a method for manufacturing a magnetic composite material is shown in Figure 2. First, as shown in Figure 2(a), magnetic powder 41 and liquid resin material 42 are prepared. Next, as shown in Figure 2(b), the resin material 42 and magnetic powder 41 are mixed and stirred. Next, as shown in Figure 2(c), the mixture is heated and molded, and a magnetic member 6 of the desired shape is completed as shown in Figure 2(d).

[0046] The magnetic member 6 (see FIG. 1) disposed in the core-less region 7 may be a powder magnetic core. A powder magnetic core is formed by compressing and solidifying (molding) insulatingly coated magnetic powder (together with nonmagnetic or insulating materials as needed). The magnetic member 6 may also be a sintered magnetic core formed by compressing and molding magnetic powder (together with nonmagnetic or insulating materials as needed) and then sintering it. The magnetic member 6 may also have a nanogranular structure. A nanogranular structure is a structure in which magnetic metal particles of nm (nanometer) size are uniformly dispersed in an insulating matrix such as ceramics.

[0047] Furthermore, multiple types of magnetic members 6 differing in at least one of magnetic permeability and saturation magnetic flux density may be provided in the coreless region 7. For example, multiple types of magnetic members 6 may be provided in the coreless region 7 depending on the requirements of the rotating electric machine's characteristics, such as magnetic properties and mechanical strength. For example, multiple types of magnetic members 6 may be stacked and arranged in the coreless region 7 so that the stacking plane is aligned with the rotation direction of the rotor 3.

[0048] There are no limitations on the shape of the coreless region 7 (magnetic member 6), but as shown in Fig. 1, it is preferable that the cross-sectional shape of the coreless region 7 (magnetic member 6) be a shape formed by curves without corners, because the rotor core 4 is less likely to be distorted by centrifugal force even when the rotor 3 rotates at high speed. Also, it is preferable that the cross-sectional shape of the coreless region 7 (magnetic member 6) be a shape with a curve that bulges outward toward the outer periphery of the rotor core, because the rotor core 4 is less likely to be distorted by centrifugal force even when the rotor 3 rotates at high speed.

[0049] Next, the operating principle of the variable magnetic flux rotating electric machine 1 to which the present invention is applied will be described. Here, it is assumed that the variable magnetic flux rotating electric machine 1 is an electric motor (variable leakage magnetic flux motor).

[0050] 3 shows a part of the configuration diagram shown in FIG. 1, and is a schematic diagram for explaining the operation of the variable magnetic flux rotating electric machine 1. (a) of the figure shows a state without load (no current), and (b) of the figure shows a state with load (current).

[0051] The magnetic member 6 has a lower magnetic permeability than the rotor core 4. In other words, the magnetic member 6 has a higher magnetic resistance than the rotor core 4, making it more difficult for magnetic flux to pass through. The magnetic member 6 also has a lower saturation magnetic flux density than the rotor core 4. In other words, the magnetic member 6 is more susceptible to magnetic saturation than the rotor core 4.

[0052] As shown in FIG. 3(a), when there is no load, of the magnetic flux emitted from the permanent magnet 5, the main magnetic flux M links with the stator 2. Furthermore, part of the magnetic flux emitted from the permanent magnet 5 becomes leakage flux L that passes through the magnetic member 6 and leaks to the opposite pole side of the adjacent permanent magnet 5. As a result, the amount of magnetic flux of the main magnetic flux component emitted from the permanent magnet 5 toward the stator 2, i.e., the stator flux linkage, is relatively reduced, and the magnetic force of the permanent magnet 5 appears weaker.

[0053] In other words, when the current flowing through the stator winding 25 is small, such as when there is no load or a low load, the magnetic member 6 acts as a magnetic flux bypass path (leakage magnetic flux path), generating leakage magnetic flux that flows via the magnetic member 6. This reduces the back electromotive force generated in the stator winding 25 by the magnetic flux from the permanent magnet 5, thereby reducing the field-weakening current during high-speed rotation. It also reduces iron loss caused by stator flux linkage. This effect improves the efficiency of the rotating electric machine, especially in the low-load and high-speed ranges.

[0054] On the other hand, as shown in FIG. 3(b), when current is flowing through the stator winding 25, the magnetic field generated by the stator winding 25 magnetically saturates the magnetic member 6. As a result, leakage magnetic flux from the permanent magnet 5 no longer passes through the magnetic member 6, and the main magnetic flux M component linking to the stator 2 increases relatively. In other words, the leakage magnetic flux L leaking within the rotor 3 when no current is flowing through the stator winding 25 can be efficiently converted into stator flux linkage. This allows the variable magnetic flux rotating electric machine 1 to output high torque equivalent to when there is no leakage of magnetic flux from the permanent magnet 5. When the stator current flows, the main magnetic flux M from the permanent magnet 5 is attracted toward the stator 2 in the direction of rotation of the rotor 3, as shown by the arrow.

[0055] In this way, the variable magnetic flux rotating electric machine 1 can change the magnetic path of a portion of the magnetic flux (leakage magnetic flux) emitted from the permanent magnets 5 of the rotor 3 by the action of the load current (stator current) applied to the stator winding 25. Due to this feature, the variable magnetic flux rotating electric machine 1 can change the stator flux linkage by controlling the stator current, and therefore the magnetic force of the permanent magnets 5 of the rotor 3 can be made variable by current control. For this reason, the variable magnetic flux rotating electric machine 1 can be used as a "variable magnetic flux" rotating electric machine.

[0056] [Second embodiment] Fig. 4 shows a partial configuration diagram of another variable magnetic flux rotating electric machine 1a to which the present invention is applied, shown in a cross section perpendicular to the rotation axis direction. Note that the same components as those already explained are given the same reference numerals, and detailed explanations will be omitted. Fig. 4 is a diagram corresponding to Fig. 3 showing the first embodiment, and Fig. 4(a) shows a state without load (no current), and Fig. 4(b) shows a state with load (current).

[0057] 4, the variable magnetic flux rotating electric machine 1a is provided with a magnetic member 6a in the coreless region 7, the magnetic member 6a having a lower magnetic permeability and a lower saturation magnetic flux density than the rotor core 4. In addition to the magnetic member 6a, the variable magnetic flux rotating electric machine 1a is also provided with a non-magnetic member 9 in the coreless region 7. The other configurations of the variable magnetic flux rotating electric machine 1a are the same as those of the variable magnetic flux rotating electric machine 1 described in the first embodiment.

[0058] As shown in the figure, in the coreless region 7, magnetic members 6a are arranged in approximately 60% of the region on the outer periphery of the rotor 3, which is closer to the stator winding 25, and non-magnetic members 9 are arranged in approximately 40% of the region on the central side of the rotor 3. The coreless region 7 is filled with the magnetic members 6a and the non-magnetic members 9 without any gaps. By changing the ratio of the magnetic members 6a to the non-magnetic members 9, it is possible to adjust the characteristics of the rotating electric machine, such as the magnetic characteristics, torque characteristics, and mechanical strength.

[0059] The magnetic member 6a is made of the same material as the magnetic member 6 already described.

[0060] The non-magnetic member 9 is formed of a material that exhibits almost no magnetism (a material that is not ferromagnetic). The non-magnetic member 9 has electrical insulation properties. The non-magnetic member 9 is a member with a low relative magnetic permeability, for example, a relative magnetic permeability of 2 or less. The material of the non-magnetic member 9 is not limited, and examples thereof include resin, ceramic, and non-magnetic metal. When the non-magnetic member 9 is a resin, for example, a thermosetting resin or a thermoplastic resin can be used. Examples of thermosetting resins include epoxy resin, phenolic resin, melamine resin, and silicone resin. Epoxy resin is preferably used because of its dimensional stability, water resistance, chemical resistance, and electrical insulation properties. Examples of thermoplastic resins include acrylic resin, polytetrafluoroethylene, polyamide, polyacetal, ABS resin, and AS resin.

[0061] It is also possible to provide a gap instead of the non-magnetic member 9 without disposing the non-magnetic member 9. Alternatively, the non-magnetic member 9 and the gap may be provided. That is, in addition to the magnetic member 6, at least one of the gap and the non-magnetic member 9 may be provided in the core-free region 7. The relative permeability of the gap is approximately 1.

[0062] The operation of the variable magnetic flux rotating electric machine 1a will be described.

[0063] The magnetic member 6a has a lower magnetic permeability than the rotor core 4. The non-magnetic member 9 has an even lower magnetic permeability than the magnetic member 6a. In other words, the magnetic member 6a has a higher magnetic resistance than the rotor core 4, making it more difficult for magnetic flux to pass through, and the non-magnetic member 9 has an even higher magnetic resistance than the magnetic member 6a, making it even more difficult for magnetic flux to pass through. In addition, the magnetic member 6a has a lower saturation magnetic flux density than the rotor core 4. In other words, the magnetic member 6a is more likely to become magnetically saturated than the rotor core 4. The non-magnetic member 9 does not become magnetically saturated.

[0064] As shown in FIG. 4(a), when there is no load, of the magnetic flux emitted from the permanent magnet 5, the main magnetic flux M interlinks with the stator 2. Furthermore, part of the magnetic flux emitted from the permanent magnet 5 becomes leakage flux L that passes through the magnetic member 6a and leaks to the opposite pole side of the adjacent permanent magnet 5. As a result, the amount of magnetic flux of the main magnetic flux component emitted from the permanent magnet 5 toward the stator 2, i.e., the stator flux linkage, is relatively reduced, and the magnetic force of the permanent magnet 5 appears weaker.

[0065] On the other hand, as shown in FIG. 4(b), when current is flowing through the stator winding 25, the magnetic field generated by the stator winding 25 does not magnetically saturate the rotor core 4, but does magnetically saturate the magnetic member 6a. As a result, leakage magnetic flux from the permanent magnet 5 does not pass through the magnetic member 6a, and the main magnetic flux M component linking to the stator 2 increases relatively. In other words, the leakage magnetic flux L leaking within the rotor 3 when no current is flowing through the stator winding 25 can be efficiently converted into stator flux linkage. This allows the variable magnetic flux rotating electric machine 1a to output high torque equivalent to that in a state in which magnetic flux from the permanent magnet 5 is not leaking. As the stator current flows, the main magnetic flux M from the permanent magnet 5 is attracted toward the stator 2 in the direction of rotation of the rotor 3, as indicated by the arrow.

[0066] In this way, the variable magnetic flux type rotating electric machine 1a, like the variable magnetic flux type rotating electric machine 1, can change the magnetic path of a portion of the magnetic flux (leakage magnetic flux) emitted from the permanent magnets 5 provided in the rotor 3 by the action of the load current (stator current) applied to the stator winding 25, and can be used as a ``variable magnetic flux type'' rotating electric machine.

[0067] In the above example, the magnetic member 6a and the non-magnetic member 9 (gap) are arranged in the core-free region 7 closer to the outer periphery of the rotor 3, and the non-magnetic member 9 (gap) is arranged closer to the center of the rotor 3. However, depending on the requirements of the characteristics of the rotating electric machine, such as magnetic properties and mechanical strength, the non-magnetic member 9 (gap) may be arranged closer to the outer periphery of the rotor 3, and the magnetic member 6a may be arranged closer to the center of the rotor 3. [Example]

[0068] [Magnetic properties of magnetic composite materials] Magnetic composite materials were prototyped as the magnetic members 6, 6a to be placed in the coreless region 7, and their magnetic properties were measured. Magnetic composite material A was prototyped using sendust as the magnetic powder and epoxy resin as the resin. The magnetic powder blend ratio was 69% by volume. Magnetic composite material B was prototyped using amorphous iron as the magnetic powder and epoxy resin as the resin. The magnetic powder blend ratio was 60% by volume. The manufacturing method was as explained in Figure 2. The magnetic properties of the electromagnetic steel plate (10JNHF600 manufactured by JFE Steel Corporation) were measured using the properties in the specifications published by the manufacturer.

[0069] Figure 5 shows the magnetic hysteresis curves of magnetic composite material A, magnetic composite material B, and electromagnetic steel sheet E. The horizontal axis is the magnetic field, and the vertical axis is the magnetic flux density. The relative permeability of magnetic composite material A was μr = 16, and that of magnetic composite material B was μr = 9. The relative permeability of electromagnetic steel sheet E was in the range of several thousand to 10,000. Magnetic composite material A saturated at a lower magnetic field strength than magnetic composite material B.

[0070] Figure 6 shows the iron loss of magnetic composite material A, magnetic composite material B, and electromagnetic steel plate E. The horizontal axis is magnetic flux density, and the vertical axis is iron loss. Magnetic composite material A had the smallest iron loss.

[0071] From this result, it was found that magnetic composite material A can be preferably used.

[0072] [Simulation using electromagnetic field analysis] Simulations were performed using electromagnetic field analysis on the motor model of embodiment 1 shown in Figures 1 and 3 as Example 1, and the motor model of embodiment 2 shown in Figure 4 as Example 2. Simulations were performed on magnetic flux density distribution, torque characteristics, efficiency maps, and stress distribution. As a comparative example, a similar simulation was performed on the motor model of the rotating electrical machine described in the background art shown in Figure 20. JMAG-Designer (x64) Ver. 19.0 was used as the electromagnetic field analysis software.

[0073] In Examples 1 and 2, the magnetic composite material A using sendust was used as the magnetic member, and simulations were carried out using the measured magnetic properties.

[0074] [Motor magnetic flux density distribution] First, Figure 7 shows the magnetic flux density distribution of the comparative example. Figure (a) shows the case with no load (no current), and Figure (b) shows the case with a load (current). As Figure (a) shows, when there is no load, the magnet flux is short-circuited and there is little magnetic flux linking to the stator. On the other hand, as Figure (b) shows, there is more magnetic flux linking to the stator when there is a load than when there is no load. In this way, it can be seen that the amount of magnetic flux of the permanent magnet linking to the stator can be controlled.

[0075] Figure 8 shows the magnetic flux density distribution in Example 1. Figure 8(a) shows the case with no load, and Figure 8(b) shows the case with a load. As Figure 8(a) shows, when there is no load, there is magnetic flux from the magnet that passes through the magnetic member, and there is little magnetic flux that interlinks with the stator. It can also be seen that there is magnetic flux from the magnet that short-circuits via the thin core wall 12 in the rotor (see Figure 1).

[0076] On the other hand, as shown in Figure 8(b), the magnetic composite material becomes magnetically saturated and more magnetic flux interlinks with the stator when there is a load than when there is no load. This shows that the amount of magnetic flux from the permanent magnet that interlinks with the stator can be controlled.

[0077] Figure 9 shows the magnetic flux density distribution in Example 2. Figure 9(a) shows the case with no load, and Figure 9(b) shows the case with a load. As Figure 9(a) shows, when there is no load, there is magnetic flux from the magnet that passes through the magnetic members, and there is little magnetic flux that interlinks with the stator. It can also be seen that almost no magnetic flux passes through the non-magnetic members. It can also be seen that there is magnetic flux from the magnet that short-circuits via the thin core wall 12 (see Figure 1) inside the rotor.

[0078] On the other hand, as shown in Figure 9(b), it can be seen that there is more magnetic flux linking the stator when there is a load than when there is no load. This shows that the amount of magnetic flux of the permanent magnet linking the stator can be controlled.

[0079] [Motor torque characteristics] Figure 10 shows the ideal torque characteristics of a variable magnetic flux rotating electric machine. When control is performed to reduce the magnetic flux of the permanent magnet, that is, when variable magnetic flux control (field-weakening control) is in effect, the torque constant (back electromotive force constant) decreases in proportion to the square of the current, as indicated by the arrow in the figure. Variable magnetic flux control is performed when the motor is unloaded or under a light load. Note that with a normal motor that does not use variable magnetic flux control, torque is proportional to the current, so the straight dashed line in the figure represents the torque characteristics when there is no load or a light load.

[0080] FIG. 11 shows the torque characteristics of each motor obtained by simulation for currents of 0 to 40 A. FIG. 12 shows the torque characteristics of each motor for an expanded current range of 5 to 15 A, and FIG. 13 shows the torque characteristics of each motor for an expanded current range of 30 to 40 A. As can be seen from FIG. 11, in the current range of 0 to 30 A, Examples 1 and 2 and the Comparative Example all have torques lower than the approximate straight line indicated by the dashed line. This indicates that variable magnetic flux control is possible. Note that the reference example shown in each figure is an example in which there is no core-free region 7 (magnetic member 6) between the permanent magnets 5, and only the rotor core 4 is present.

[0081] The current range of 5 to 15 A shown in Figure 12 falls within the variable magnetic flux region. From the figure, it can be seen that Example 1 has the smallest torque. Example 2 has torque that is almost the same as the comparative example. Example 1 can reduce the torque constant by up to 16% compared to the approximate straight line (see Figure 13), and is effective in reducing the field-weakening current during high-speed rotation.

[0082] The high torque region is in the current range of 30 to 40 A shown in Fig. 13. It can be seen from the figure that Examples 1 and 2 and the comparative example generate almost the same high torque.

[0083] [Motor efficiency map] Figure 14 shows the efficiency map of the motor of the comparative example. The horizontal axis is rotation speed (rpm), the left vertical axis is torque (Nm), and the right vertical axis is efficiency (%). The maximum rotation speed in the high efficiency region, where the efficiency is 93% or more, was approximately 3200 rpm.

[0084] 15 shows an efficiency map of the motor of Example 1. The maximum rotation speed in the high efficiency region where the efficiency is 93% or more is approximately 3600 rpm.

[0085] 16 shows an efficiency map of the motor of Example 2. The maximum rotation speed in the high efficiency region where the efficiency is 93% or more is approximately 3400 rpm.

[0086] From the above simulation results, it was found that Example 1 could be used most efficiently up to the high rotation speed range, followed by Example 2 and the comparative example.

[0087] [Motor stress distribution] Figure 17 shows the simulation results of stress distribution for each motor. The figure shows the von Mises stress at a rotation speed of 5,000 rpm. In the comparative example shown in Figure 17(a), a stress of 12.1 MPa is applied to the thinnest part (thin core wall) near the outer periphery of the rotor core, and a stress of 38.1 MPa is applied to the wall between the permanent magnet and the core gap. In Example 1 shown in Figure 17(b), a stress of 8.1 MPa (28% reduction from the comparative example) is applied to the thinnest part (thin core wall) near the outer periphery of the rotor core, and a stress of 18.9 MPa (50% reduction from the comparative example) is applied to the wall between the permanent magnet and the coreless area. These results show that Example 1 can reduce the stress applied to the rotor core compared to the comparative example.

[0088] [Torque characteristics relative to the motor stator current phase] 18 and 19 show the simulation results of the torque characteristics versus the stator current phase for each motor. It can be seen that torque at high currents is less likely to drop with respect to phase changes in Example 2 than in Example 1. The fact that torque characteristics are less likely to drop at high torque has the advantage of reducing copper loss and increasing maximum generated torque at high currents (i.e., large torque). [Explanation of symbols]

[0089] 1 and 1a are variable magnetic flux type rotating electric motors, 2 is a stator, 3 is a rotor, 4 is a rotor core, 5 is a permanent magnet, 6 and 6a are magnetic materials, 7 is a core-free region, 9 is a non-magnetic material, 11 is an air gap, 12 is a thin-walled core, 21 is a stator core, 22 is a tooth, 23 is a slot, 25 is a stator winding, 41 is a magnetic powder, 42 is a resin material, 201 is a variable magnetic flux type rotating electric motor, 211 is a stator, 212 is a rotor, 213 is a permanent magnet, 220 is a stator winding, 221 is a tooth, 231 is a rotor core, 234 is a magnetic barrier, 235 is a magnetic barrier, 236 is a magnetic flux bypass path, A is a magnetic composite material using sendust, B is a magnetic composite material using amorphous iron, E is an electromagnetic steel plate, L is leakage flux, and M is main magnetic flux.

Claims

1. A variable magnetic flux type rotating electric machine including a rotor and a stator that generates a rotating magnetic field relative to the rotor, The rotor has a rotor core made of a soft magnetic material and a plurality of permanent magnets embedded therein so as to be arranged with their polarities alternated along the circumferential direction of the rotor core, a coreless region where the rotor core is not present is provided between adjacent permanent magnets, and a magnetic member having a lower magnetic permeability and a lower saturation magnetic flux density than the rotor core is disposed in the coreless region, the magnetic member is a magnetic composite material in which magnetic powder, which is a powder of a soft magnetic material, is mixed with resin; The coreless region is entirely surrounded by the rotor core, and the magnetic member is disposed throughout the coreless region, the magnetic member is capable of being magnetically saturated by application of the rotating magnetic field for rotating the rotor, When the rotating magnetic field is weak and the magnetic member is not magnetically saturated, part of the magnetic flux emitted from the permanent magnet becomes leakage flux that passes through the magnetic member and leaks to the adjacent permanent magnet, and the magnetic flux linking to the stator side is relatively reduced, A variable magnetic flux type rotating electric motor characterized in that when the rotating magnetic field of a strength that causes magnetic saturation is applied to the magnetic member, the magnetic flux emitted from the permanent magnet does not pass through the magnetic member, and the magnetic flux linking to the stator side increases relatively.

2. A variable flux type rotating electric motor as described in claim 1, characterized in that the relative permeability of the magnetic member is 5 or more and 100 or less, and the saturation magnetic flux density of the magnetic member is 0.2 T or more and 0.8 T or less.

3. 3. The variable magnetic flux rotating electric machine according to claim 1, wherein the coreless region is provided with a plurality of types of magnetic members each having different characteristics of at least one of magnetic permeability and saturation magnetic flux density.

4. 4. The variable magnetic flux rotating electric machine according to claim 1, wherein the magnetic powder is at least one of sendust, amorphous iron, and permalloy.

5. 5. A variable magnetic flux rotating electric machine according to claim 1, wherein the cross-sectional shape of the coreless region in a cross section perpendicular to the rotation axis direction of the rotor is a shape composed of curves without corners.

6. 6. A variable magnetic flux rotating electric motor according to claim 1, wherein the cross-sectional shape of the coreless region in a cross section perpendicular to the rotational axis direction of the rotor has a curve that bulges out toward the outer periphery of the rotor core.

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