Variable flux rotating electric machine

Abstract

This invention provides a variable flux rotating electric machine that, with a simple configuration, can vary the pressure applied to the reverse magnetostrictive member according to the rotational speed of the rotor. [Solution] The variable flux rotating electric machine 1 comprises a rotor 2 and a stator 3. The rotor 2 has a rotor core 4, a plurality of permanent magnets 5, a housing section 6 which is a region without the rotor core 4 formed between adjacent permanent magnets 5, and an inverse magnetostrictive member 7 housed in the housing section 6 under pressure. The permeability of the inverse magnetostrictive member 7 changes such that its permeability decreases as the pressure increases and increases as the pressure decreases. The housing section 6 has an outer peripheral wall 8 that closes the outer circumference of the rotor 2. The outer peripheral wall 8 is formed to be deformable outward when the rotor 2 rotates at high speed more than when it rotates at low speed, and the pressure applied to the inverse magnetostrictive member 7 can be changed by the deformation of the outer peripheral wall 8.

Description

Technical Field

[0001] The present invention relates to a variable magnetic flux type rotating electrical machine including a rotor and a stator that generates a rotating magnetic field with respect to the rotor, and having a plurality of permanent magnets embedded therein so as to be arranged along the circumferential direction of the rotor core.

Background Art

[0002] Patent Document 1 describes a rotor for a rotating electrical machine including a rotatable rotor core (rotor core), a plurality of permanent magnets respectively inserted into a plurality of magnet insertion holes formed in the rotor core, and a plurality of flux barriers formed between adjacent magnet insertion holes of the rotor core, and a flux short-circuit member disposed in each of the flux barriers to form a path of magnetic flux from one first pole of an adjacent permanent magnet to the other second pole. The flux short-circuit member is made of a giant magnetostrictive material (inverse magnetostrictive material), and when the rotor rotates at a high speed, the permeability of the giant magnetostrictive material is improved more than when it rotates at a low speed, and the short-circuit magnetic flux from the first pole to the second pole is increased.

[0003] In the rotor for a rotating electrical machine of the first embodiment described in the same document, the giant magnetostrictive material is pressurized by biasing a weight toward the giant magnetostrictive material with a compression spring. When the rotational speed of the rotor becomes a predetermined value or more, the pressing force by the compression spring decreases due to the centrifugal force applied to the weight and the flux short-circuit member. When the pressing force decreases, the permeability of the giant magnetostrictive material increases.

[0004] Also, in the rotor for a rotating electrical machine of the second embodiment described in the same document, a pressing mechanism for pressing a giant magnetostrictive plate piece is arranged beside the rotor. The pressing mechanism includes a linear solenoid and a small generator. As the rotational speed of the rotor increases, the power generation amount of the small generator increases, and the linear solenoid pulls the plunger portion in the direction of the small generator against the biasing force of the compression spring. As a result, the pressing force on the giant magnetostrictive plate piece decreases, and the permeability of the giant magnetostrictive plate piece increases.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-343842 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The rotor (rotor for a rotating electric machine) of the first embodiment described in Patent Document 1 has the problem of requiring a complex configuration in which a weight is biased against the reverse magnetostrictive member (magnetic flux short-circuiting member) by a compression spring. Furthermore, the rotor (rotor for a rotating electric machine) of the second embodiment described in the same document has the problem of requiring an even more complex configuration, such as a linear solenoid and a small generator, to adjust the pressure applied to the reverse magnetostrictive member (magnetic flux short-circuiting member).

[0007] The present invention was made to solve the aforementioned problems, and aims to provide a variable flux rotating electric machine that has a simple configuration while being able to vary the pressing force on the reverse magnetostrictive member according to the rotational speed of the rotor. [Means for solving the problem]

[0008] The variable flux rotating electric machine according to claim 1 is a variable flux rotating electric machine comprising a rotor and a stator that generates a rotating magnetic field for the rotor, wherein the rotor comprises a rotor core made of a soft magnetic material, a plurality of permanent magnets embedded inside the rotor core so as to be arranged alternately with alternating polarities along the circumferential direction of the rotor core, a housing portion which is a region without the rotor core formed between adjacent permanent magnets, and an inverse magnetostrictive member housed in the housing portion under pressure, wherein the permeability of the inverse magnetostrictive member changes such that the permeability decreases with increasing pressure and increases with decreasing pressure, the housing portion has an outer peripheral wall that closes the outer circumferential side of the rotor, the outer peripheral wall is formed to be deformable outward when the rotor rotates at high speed more than when it rotates at low speed, and the pressure applied to the inverse magnetostrictive member can be changed by the deformation of the outer peripheral wall.

[0009] The variable magnetic flux rotating electric machine described in claim 2 is the same as that described in claim 1, characterized in that the reverse magnetostrictive member is provided with a clamping allowance, and the reverse magnetostrictive member is housed in the housing portion with the clamping allowance compressed.

[0010] The variable magnetic flux rotating electric machine according to claim 3 is the same as that described in claim 1, characterized in that a sheet-like member having elasticity in a compressed state is disposed between the inverse magnetostrictive member and the inner wall of the housing.

[0011] The variable magnetic flux rotating electric machine according to claim 4 is the same as that according to any one of claims 1 to 3, characterized in that, when the inverse magnetostrictive member is shown in cross-section perpendicular to the rotation axis of the rotor, the width along the circumferential direction of the rotor core is wider on the outer circumference side than on the inner circumference side.

[0012] The variable magnetic flux rotating electric machine described in claim 5 is the same as that described in claim 4, wherein the inverse magnetostrictive member is formed in a substantially trapezoidal shape with an upper base and a lower base each formed by a straight line or a curve, and is arranged with the shorter upper base on the inner circumference side and the longer lower base on the outer circumference side of the rotor core.

[0013] The variable flux rotating electric machine according to claim 6 is the same as that according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed with a constant thickness.

[0014] The variable flux rotating electric machine according to claim 7 is the same as that according to any one of claims 1 to 3, characterized in that the inverse magnetostrictive member is formed with a density greater than that of the rotor core.

[0015] The variable magnetic flux rotating electric machine according to claim 8 is the same as that according to any one of claims 1 to 3, characterized in that a weight with a density greater than that of the inverse magnetostrictive member is housed in the housing.

[0016] The variable flux rotating electric machine according to claim 9 is the same as that according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed of the rotor core.

[0017] The variable flux rotating electric machine according to claim 10 is the same as that according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed separately from the rotor core. [Effects of the Invention]

[0018] In the variable flux rotating electric machine to which the present invention is applied, an inverse magnetostrictive member is housed under pressure in a housing between adjacent permanent magnets, and when the rotor rotates at high speed, the outer circumferential wall of the housing deforms outward, and the pressure applied to the inverse magnetostrictive member can be changed by this deformation of the outer circumferential wall. As a result, it is not necessary to provide a complex structure for applying pressure to the inverse magnetostrictive member, and the pressure applied to the inverse magnetostrictive member can be varied according to the rotational speed of the rotor with a simple configuration.

[0019] If the reverse magnetostrictive member is provided with a clamping allowance, and the reverse magnetostrictive member is housed in the housing while the clamping allowance is compressed, then no other configuration is required for pressurizing the reverse magnetostrictive member, resulting in a simpler configuration.

[0020] When a compressed sheet-like member is placed between the inverse magnetostrictive member and the inner wall of the housing, the degree of pressure applied to the inverse magnetostrictive member can be easily set by adjusting the shape and material of the sheet-like member, such as its thickness, despite the simple configuration.

[0021] When represented by a cross-section perpendicular to the rotation axis of the rotor, if the width of the inverse magnetostrictive member along the circumferential direction of the rotor core is formed in a shape that is wider on the outer circumferential side than on the inner circumferential side, the shape of the inverse magnetostrictive member can be enlarged, and the magnetic flux passing through the inverse magnetostrictive member during high-speed rotation can be increased. Also, by making the outer circumferential side of the inverse magnetostrictive member wider, the weight on the outer circumferential side becomes larger, so the centrifugal force of the inverse magnetostrictive member acting on the outer circumferential wall becomes larger, and the outer circumferential wall can be easily deformed. Also, by making the outer circumferential side of the inverse magnetostrictive member wider, the circumferential length of the outer circumferential wall can be increased, and the outer circumferential wall becomes easier to deform. For this reason, the change in the compressive stress of the inverse magnetostrictive member due to the rotation speed becomes larger, and the change in the magnetic permeability of the inverse magnetostrictive member can be increased.

[0022] Furthermore, when the inverse magnetostrictive member is formed in a substantially trapezoidal shape with the upper base and the lower base each formed by a straight line or a curve, and is arranged with the short upper base on the inner circumferential side of the rotor core and the long lower base on the outer circumferential side, the shape of the inverse magnetostrictive member can be made even larger, and the magnetic flux passing through the inverse magnetostrictive member during high-speed rotation can be further increased. Also, when the inverse magnetostrictive member is in a substantially trapezoidal shape, since the legs connecting the upper base and the lower base are formed in a direction that linearly spreads outward, the centrifugal force of the inverse magnetostrictive member is likely to act smoothly on the outer circumferential wall.

[0023] When the outer circumferential wall is formed with a constant thickness, the outer circumferential wall is likely to be deformed by centrifugal force. When the inverse magnetostrictive member is formed with a density greater than the density of the rotor core, the centrifugal force of the inverse magnetostrictive member acting on the outer circumferential wall can be made larger, and the outer circumferential wall is more likely to be deformed outward. When a weight with a density greater than that of the inverse magnetostrictive member is accommodated in the accommodating portion, the centrifugal force acting on the outer circumferential wall can be further increased, and the outer circumferential wall is even more likely to be deformed outward.

[0024] When the outer circumferential wall is formed by the rotor core, a simple structure can be achieved. When the outer circumferential wall is formed separately from the rotor core, the ease of deformation and the magnitude of displacement of the outer circumferential wall can be appropriately set by the shape such as the material and thickness used for the outer circumferential wall.

Brief Description of the Drawings

[0025] [Figure 1] Cross-sectional view perpendicular to the rotation axis direction of the variable magnetic flux type rotating electrical machine of the first embodiment to which the present invention is applied. [Figure 2] Graph showing the relative permeability characteristics and DC magnetization characteristics of the Tb-Dy-Fe alloy. [Figure 3] Schematic diagram showing the operating principle of the variable magnetic flux type rotating electrical machine. [Figure 4] Cross-sectional view of a part of the rotor of the variable magnetic flux type rotating electrical machine, and further an enlarged cross-sectional view of its main part (inverse magnetostrictive member). [Figure 5] Cross-sectional view of a part of the rotor of the variable magnetic flux type rotating electrical machine, and further an enlarged cross-sectional view of its main part (outer peripheral wall). [Figure 6] Graph showing the displacement of the outer peripheral wall according to the rotational speed of the rotor by structural analysis. [Figure 7] Contour diagram of the compressive stress applied to the inverse magnetostrictive member by structural analysis. [Figure 8] Contour diagram of the magnetic flux density of the permanent magnet by magnetic flux density analysis. [Figure 9] Graph showing the variable characteristics of the d-axis magnetic flux density by magnetic flux density analysis. [Figure 10] Graph showing the N-T characteristics of the variable magnetic flux type rotating electrical machine by electromagnetic field analysis. [Figure 11] Graph showing the output characteristics of the variable magnetic flux type rotating electrical machine by electromagnetic field analysis. [Figure 12] Cross-sectional view of a part of the rotor of another variable magnetic flux type rotating electrical machine to which the present invention is applied, and further an enlarged cross-sectional view of its main part (inverse magnetostrictive member and weight). [Figure 13] Cross-sectional view of a part of the rotor of still another variable magnetic flux type rotating electrical machine to which the present invention is applied, and further an enlarged cross-sectional view of its main part (inverse magnetostrictive member and sheet-like member). [Figure 14] Cross-sectional view of a part of the rotor of still another variable magnetic flux type rotating electrical machine to which the present invention is applied, and further an enlarged cross-sectional view of its main part (outer peripheral wall).

Embodiments for Carrying Out the Invention

[0026] The following describes in detail the embodiments for carrying out the invention, but the scope of the present invention is not limited to these embodiments.

[0027] [First Embodiment] Figure 1 shows a cross-sectional view perpendicular to the rotation axis of a variable flux rotating electric machine 1 to which the present invention is applied. The variable flux rotating electric machine 1 is an electric motor or a generator.

[0028] The basic configuration of the variable flux rotating electric machine 1 to which the present invention is applied is described below. The variable flux rotating electric machine 1 comprises a rotor 2 and a stator 3 that generates a rotating magnetic field for the rotor 2. The rotor 2 has a rotor core 4 made of a soft magnetic material, a plurality of permanent magnets 5 embedded inside the rotor core 4 so as to be arranged alternately with alternating polarities along the circumferential direction (circumferential direction), a housing section 6 which is a region without the rotor core 4 formed between adjacent permanent magnets 5, and an inverse magnetostrictive member 7 housed in the housing section 6 under pressure. The permeability of the inverse magnetostrictive member 7 changes such that its permeability decreases with increasing pressure and increases with decreasing pressure. The housing section 6 has an outer peripheral wall 8 that closes the outer circumference of the rotor 2. The outer peripheral wall 8 is formed to be deformable outward when the rotor 2 rotates at high speed more than when it rotates at low speed. The deformation of this outer peripheral wall 8 allows the pressure pressing on the inverse magnetostrictive member 7 to be changed. The details will be explained below.

[0029] As shown in the figure, the variable flux rotating electric machine 1 has a rotor 2 rotatably supported inside the stator 3. The rotor 2 has a rotor core 4, a plurality of permanent magnets 5, a plurality of housings 6, a plurality of reverse magnetostrictive members 7, a rotating shaft 41, and a shaft fixing member 42.

[0030] The rotor core 4 is made of a soft magnetic material and is cylindrical in shape. For example, the rotor core 4 is cylindrical in shape using a so-called laminated steel sheet structure, which consists of numerous electrical steel sheets stacked axially. The electrical steel sheets are formed by punching out ring-shaped pieces of metal steel sheets with high magnetic permeability.

[0031] Inside the rotor core 4, multiple permanent magnets 5 are arranged circumferentially near the peripheral portion facing the stator 3, at equal intervals from each other, and with adjacent permanent magnets 5 having opposite polarities. In this embodiment, as an example, a rotor 2 (rotor core 4) having a 6-pole structure with 6 permanent magnets 5 arranged circumferentially is shown.

[0032] The permanent magnet 5 is fitted into a gap formed in the rotor core 4 and fixed inside the rotor core 4. The permanent magnet 5 is magnetized in the radial direction of the rotor 2, as shown by the "S" pole and "N" pole in the figure.

[0033] Inside the rotor core 4, a housing section 6 is formed between the magnetic poles of adjacent permanent magnets 5. As an example, the housing section 6 is formed by punching out a hole in the rotor core 4. Because the housing section 6 is formed inside the rotor core 4, a thin outer wall 8, formed by the rotor core 4, is formed outside the housing section 6 (on the outer circumference side of the rotor core 4). This outer wall 8 closes off the area of ​​the housing section 6 from the outside, making the housing section 6 a room-like structure. An inverse magnetostrictive member 7 is housed in the housing section 6.

[0034] The reverse magnetostrictive member 7 is housed in the housing 6 under pressure from the inner wall of the housing 6. The inner wall of the housing 6 includes the inner wall of the outer periphery wall 8. Since this embodiment is an example of a 6-pole structure, the rotor 2 is provided with 6 reverse magnetostrictive members 7 (housing 6), the same number as the number of poles.

[0035] The inverse magnetostrictive member 7 is made of an inverse magnetostrictive material and exhibits the so-called Villari effect, where its permeability changes such that it decreases as the applied pressure (stress) increases and increases as the pressure decreases. In other words, the inverse magnetostrictive member 7 makes it difficult for magnetic flux to pass through when the applied pressure is high, and easier for magnetic flux to pass through when the applied pressure is low.

[0036] Known materials can be used as such inverse magnetostrictive materials. Examples of inverse magnetostrictive materials include Tb-Dy-Fe alloys and Fe-Ga alloys. Tb-Dy-Fe alloys, which exhibit a large change in permeability with respect to stress changes, can be preferably used as the inverse magnetostrictive material.

[0037] Figure 2 shows the relative permeability and DC magnetization characteristics of Tb-Dy-Fe alloys. It can be seen that the magnetization characteristics of inverse magnetostrictive materials change significantly when stress is applied.

[0038] As shown in Figure 1, the rotation shaft 41 of the rod-shaped rotor 2 is fixed to the rotor core 4 by a shaft fixing member 42 in the center of the rotor core 4. The rotation shaft 41 and shaft fixing member 42 are the same as those of known rotating electric machines. The rotor 2 is supported so as to be rotatable with respect to the stator 3, with respect to the rotation shaft 41 as the axis.

[0039] The stator 3 has a structure similar to that of a known rotating electric machine and is formed in an annular shape that surrounds the rotor 2. The stator 3 has a ring-shaped stator core 31, a plurality of teeth 32 formed to protrude from the inner circumference of the stator core 31, slots 33 which are spaces between adjacent teeth 32, and stator windings 34 wound around the teeth 32 and housed in the slots 33. The stator core 31 (teeth 32) is formed of a soft magnetic material (soft magnetic body), such as electrical steel sheet. A specific illustration of the stator windings 34 is omitted. The stator windings 34 have windings corresponding to the number of poles of the rotor 2 in order to apply a rotating magnetic field to the rotor 2.

[0040] Figure 3 shows the operating principle of the variable flux rotating electric machine 1 to which the present invention is applied. The figure also shows a part of the variable flux rotating electric machine 1. The magnetic flux is schematically represented by a dashed line in the figure.

[0041] At low rotation speeds as shown in Figure (a), the reverse magnetostrictive member 7 is subjected to compressive stress from its surroundings (thick arrow in the figure), resulting in a low magnetic permeability of the reverse magnetostrictive member 7. Therefore, the reverse magnetostrictive member 7 acts as a flux barrier, and much of the magnetic flux emanating from the permanent magnet 5 bypasses the reverse magnetostrictive member 7 and links to the stator 3.

[0042] On the other hand, at high rotational speeds as shown in Figure (b), the outer circumferential wall 8 of the rotor 2 deforms (displaces) outward due to the centrifugal force, and the area of ​​the housing 6 expands. As a result, the compressive stress on the inverse magnetostrictive member 7 decreases, and the permeability of the inverse magnetostrictive member 7 increases. Consequently, the magnetic flux that short-circuits within the rotor 2 through the inverse magnetostrictive member 7 increases. In this way, the variable flux rotating electric machine 1 becomes a 'variable flux' rotating electric machine in which the path of the magnetic flux is varied depending on the rotational speed (revolutions per unit time) of the rotor 2.

[0043] When the rotor 2 rotates at high speed, the magnetic flux of the permanent magnets 5 linked to the stator 3 decreases, which reduces the back electromotive force caused by the linked magnetic flux of the stator 3. As a result, the operating range of the variable flux rotating electric machine 1 can be extended to the high-speed region.

[0044] Figure 4 shows a cross-sectional view of a part of the rotor 2, and an enlarged view of its main components.

[0045] The inverse magnetostrictive member 7 needs to be housed in the housing 6 under pressure from its surroundings (under compressive stress). In this embodiment, the inverse magnetostrictive member 7 is provided with interference fits D1 to D4, and the inverse magnetostrictive member 7 is housed in the housing 6 with the interference fits D1 to D4 compressed.

[0046] The inverse magnetostrictive member 7 is formed to have a cross-sectional shape that is larger than the cross-sectional shape of the housing 6 by the amount of the interference fit D1 to D4. The shape shown by the dashed line around the inverse magnetostrictive member 7 in the enlarged view is the shape of the inverse magnetostrictive member 7 including the interference fit D1 to D4, that is, the shape before it is pressed into the housing 6. The interference fit of the inverse magnetostrictive member 7 is represented as interference fit D1 on the outer circumference side (upper side of the figure) of the rotor 2, interference fit D2 on the inner circumference side (lower side of the figure), interference fit D3 on the left side, and interference fit D4 on the right side.

[0047] By applying pressure to house (press-fit) the inverse magnetostrictive member 7, which is larger than the housing portion 6 by the amount of the overlap D1 to D4, the inverse magnetostrictive member 7 comes into contact with the inner wall of the housing portion 6 and is pressed against it, compressing it by the amount of the overlap D1 to D4, and pressurizing the inverse magnetostrictive member 7 from the inner wall of the housing portion 6.

[0048] The interference fit D1 to D4 should be set appropriately depending on the size and shape of the inverse magnetostrictive member 7, the inverse magnetostrictive material, and the compressive stress. When the outer peripheral wall 8 deforms outward, it is necessary to reduce the pressure (compressive stress) on the inverse magnetostrictive member 7. Therefore, the interference fit D1 and D2 in the radial direction (towards the outer peripheral wall 8) of the rotor 2 are important factors in stress change. Accordingly, it is preferable to make the interference fit D1 on the outer peripheral side and the interference fit D2 on the inner peripheral side larger than the left and right interference fit D3 and D4. In some cases, only the interference fit D1 on the outer peripheral side and the interference fit D2 on the inner peripheral side may be set, and the left and right interference fit D3 and D4 may be omitted. There are no limitations on the values ​​of the interference fit D1 to D4, but as an example, the interference fit D1 on the outer peripheral side and the interference fit D2 on the inner peripheral side may be set to 0.005 to 0.1 mm, and the left and right interference fit D3 and D4 may be set to 0 to 0.05 mm. Since the overlap D1 in contact with the outer perimeter wall 8 is particularly important as a factor in stress changes, the overlap D1 on the outer perimeter side may be set to be larger than the overlap D2 on the inner perimeter side.

[0049] The compressive stress applied to the inverse magnetostrictive member 7 housed in the housing section 6 can be appropriately set to correspond to the desired magnetic permeability. The compressive stress applied to the inverse magnetostrictive member 7 depends on the inverse magnetostrictive material, but when the rotor 2 is stationary, it is preferably at least 10 MPa, preferably at least 20 MPa, more preferably at least 30 MPa, and even more preferably at least 40 MPa.

[0050] As mentioned above, the reverse magnetostrictive member 7 is press-fitted into the housing section 6. A known press-fitting machine can be used for press-fitting. Alternatively, the reverse magnetostrictive member 7 may be cooled to shrink it before being housed in the housing section 6, or the housing section 6 may be heated to expand it before the reverse magnetostrictive member 7 is housed in the housing section 6. In this case, as it returns to room temperature, it will try to return to its original shape, so the reverse magnetostrictive member 7 will be under pressure from the inner wall of the housing section 6.

[0051] As shown in the figure, when the reverse magnetostrictive member 7 is represented in a cross-section perpendicular to the rotation axis of the rotor 2, it is preferable that the width of the reverse magnetostrictive member 7 (housing portion 6) along the circumferential direction of the rotor core 4 is wider on the outer circumference side than on the inner circumference side of the rotor core 4.

[0052] In this way, by widening the outer circumference of the reverse magnetostrictive member 7, the shape of the reverse magnetostrictive member 7 can be enlarged. By enlarging the shape of the reverse magnetostrictive member 7, the magnetic flux passing through the reverse magnetostrictive member 7 can be increased at high rotational speeds. In addition, by widening the outer circumference of the reverse magnetostrictive member 7, the weight of the reverse magnetostrictive member 7 becomes greater on the outer circumference, which increases the centrifugal force of the reverse magnetostrictive member 7 acting on the outer wall 8, making it easier to deform the outer wall 8.

[0053] Furthermore, by widening the outer circumference of the inverse magnetostrictive member 7, the circumferential length of the outer wall 8 can be increased. A longer outer wall 8 makes it easier for the outer wall 8 to deform outwards. Also, the amount of displacement of the outer wall 8 can be increased. When the outer wall 8 deforms outwards more easily, it can be deformed from a low rotational speed. In addition, if the amount of displacement of the outer wall 8 can be increased, the change in compressive stress of the inverse magnetostrictive member 7 with respect to rotational speed will be larger, and the change in the permeability of the inverse magnetostrictive member 7 can be increased.

[0054] The figure shows an example in which the inverse magnetostrictive member 7 is formed with a roughly trapezoidal shape, where the outer circumference of the rotor core 4 is wider than the inner circumference. The inverse magnetostrictive member 7 has a roughly trapezoidal shape with an upper base and a lower base formed by straight or curved lines, and is positioned with the shorter upper base on the inner circumference side and the longer lower base on the outer circumference side of the rotor core 4 (the enlarged view in the figure shows a portion where the roughly trapezoidal inverse magnetostrictive member 7 with a short upper base and a long lower base is positioned upside down).

[0055] When the reverse magnetostrictive member 7 is formed in such a roughly trapezoidal shape, the shape of the reverse magnetostrictive member 7 can be made larger, and the magnetic flux passing through the reverse magnetostrictive member 7 can be increased at high rotational speeds. In addition, when the reverse magnetostrictive member 7 is roughly trapezoidal, the legs connecting the upper and lower bases are formed to spread outwards in a straight line, so the centrifugal force of the reverse magnetostrictive member 7 can be applied smoothly to the outer wall 8.

[0056] The cross-sectional shape of the inverse magnetostrictive member 7 may be set as appropriate according to the need. For example, the cross-sectional shape of the inverse magnetostrictive member 7 may be rectangular, triangular, polygonal, circular, elliptical, or any other shape. Furthermore, each side of the cross-sectional shape of the inverse magnetostrictive member 7 may be curved, and the corners may be rounded.

[0057] The figure shows an example where the lower base (outer edge) of the roughly trapezoidal inverse magnetostrictive member 7 is formed with a curve so as to be parallel to the outer circumference of the rotor core 4, that is, an example where the thickness of the outer wall 8 is formed to be constant. When the thickness of the outer wall 8 is constant, it is preferable because the outer wall 8 is easily deformed by centrifugal force. If the lower base of the roughly trapezoidal inverse magnetostrictive member 7 is formed with a straight line, the thickness of the central part of the outer wall 8 will be thicker, so the strength of the outer wall 8 will increase and it will be less likely to deform by centrifugal force.

[0058] The greater the weight of the inverse magnetostrictive member 7, the greater the centrifugal force acting on the outer wall 8, which is preferable because it makes the outer wall 8 more likely to deform outward at high rotational speeds. Therefore, it is preferable that the inverse magnetostrictive member 7 is formed with a density greater than that of the rotor core 4. When the density of the inverse magnetostrictive member 7 is greater than that of the rotor core 4, the centrifugal force acting on the outer wall 8 can be increased, making the outer wall 8 more likely to deform outward. When the amount of outward displacement of the outer wall 8 increases, the change in compressive stress of the inverse magnetostrictive member 7 with respect to rotational speed increases, and the change in the permeability of the inverse magnetostrictive member 7 can be increased.

[0059] The thickness of the outer periphery wall 8 should be appropriately set such that it can press the inverse magnetostrictive member 7 when the rotor 2 is stationary or rotating at low speeds, and that when the rotor 2 is rotating at high speeds (above a predetermined high rotational speed), the outer periphery wall 8 deforms by centrifugal force to a predetermined displacement amount or more, causing the inverse magnetostrictive member 7 to have a magnetic permeability of a desired level or higher.

[0060] The thickness of the outer periphery wall 8 depends on the material and shape of the rotor core 4, the rotational speed of the rotor 2, and the material and shape of the reverse magnetostrictive member 7, but is, for example, 0.5 mm to 2 mm. The displacement of the outer periphery wall 8 when the rotor 2 is rotating at a predetermined high rotational speed is, for example, 0.01 mm to 0.1 mm.

[0061] [Analysis using computer simulation] [Displacement analysis of the outer wall] To investigate the displacement of the outer wall 8, a computer simulation was performed to analyze the relationship between the rotational speed of the rotor 2 and the displacement of the outer wall 8.

[0062] As analysis conditions, in the shape shown in Figures 1 and 4, the outer diameter of the stator 3 was 176.1 mm, the outer diameter of the rotor 2 was 109.2 mm, the length of the permanent magnet 5 was 3 mm, the width was 36 mm, and the upper base on the inner circumference side of the housing section 6 (reverse magnetostrictive member 7), which was formed in a roughly trapezoidal shape, was 6.95 mm, the lower base on the outer circumference side was 17.28 mm, the legs were 6.95 mm, and the thickness of the outer circumference wall 8 was 1.0 mm. Table 1 shows the specifications of the variable flux rotating electric machine 1 used in this analysis.

[0063] [Table 1]

[0064] Table 2 shows the mechanical properties of the materials used in this analysis. The mechanical properties of the stator core and rotor core (35H300) and the permanent magnet (N36Z) were taken from catalog values, while the mechanical properties of the inverse magnetostrictive material (Tb-Dy-Fe) were analyzed as shown in the table.

[0065] [Table 2]

[0066] Table 3 shows the analysis conditions used in this structural analysis.

[0067] [Table 3]

[0068] Figure 5 shows a partially enlarged cross-sectional view of the rotor 2. The coordinate system (x) of the displacement of the outer wall 8 due to centrifugal force is shown in the same figure. An example of the shape of the outer wall 8 deformed by centrifugal force is illustrated by a dashed line in the same figure. The displacement x at 0 rpm (revolutions per minute) was set to 0, and the radial displacement Δx was calculated. Figure 6 shows the change in the displacement of the outer wall 8 according to the rotational speed of the rotor 2. The displacement increases quadratically, and a displacement of approximately 0.028 mm was observed at 20,000 rpm.

[0069] [Pressure and stress analysis] From the displacement analysis described above, it was confirmed that the outer wall 8 deformed to nearly 0.03 mm. Therefore, the interference fit of the inverse magnetostrictive member 7 was set as follows so that the stress would be released at approximately 20,000 rpm, and a pressure stress analysis was performed. The upper interference fit D1 and lower interference fit D2 of the inverse magnetostrictive member 7 shown in Figure 4 were set to 0.015 mm each. The left side interference fit D3 and the right side interference fit D4 were set to 0.001 mm each. In addition, the change in compressive stress on the material due to centrifugal force was represented by subtracting the amount of displacement due to centrifugal force from the initial interference fit.

[0070] Figure 7 shows a contour map of the compressive stress applied to the inverse magnetostrictive member. At 0 rpm, it was confirmed that a compressive stress of 30 MPa or more was applied to the entire inverse magnetostrictive member, and it was confirmed that the compressive stress on the inverse magnetostrictive material was relieved as the rotational speed increased.

[0071] [Variable characteristic analysis of magnetic flux density in rotating electric machines] A magnetic flux density analysis was performed on a variable-flux rotating electric machine 1. Figure 8 shows a contour map of the magnetic flux density due to the permanent magnet. It was confirmed that at 0 rpm, the magnetic flux passing through the reverse magnetostrictive member was small, and as the rotational speed increased, the magnetic flux passing through the reverse magnetostrictive member and short-circuiting increased.

[0072] [Variable characteristic analysis of d-axis magnetic flux density] A magnetic flux density analysis was performed on the d-axis direction of a variable-flux rotating electric machine 1. Figure 9 shows the variable characteristics of the d-axis magnetic flux density. It was confirmed that the d-axis magnetic flux density decreases as the rotational speed increases. The d-axis refers to the direction of the main magnetic flux (the direction of the north pole of the permanent magnet) and is a rotating coordinate system synchronized with the rotor.

[0073] [NT characteristics analysis] An N (speed)-T (torque) characteristic analysis was performed on the variable flux rotating electric machine 1. The NT characteristics are shown in Figure 10. In the same figure, the variable flux rotating electric machine 1 of the present invention is shown as an example with a solid line. Also in the same figure, the analysis results of an IPM (Interior Permanent Magnet) motor are shown as a comparative example with a dashed line. The structure of the IPM motor is the same as the variable flux rotating electric machine 1 shown in Figure 1, but with the reverse magnetostrictive member removed. It was confirmed that the variable flux rotating electric machine 1 of the present invention expands the high-speed operating range compared to the IPM motor.

[0074] [Output Characteristics Analysis] The output characteristics of the variable flux rotating electric machine 1 were analyzed. Figure 11 shows the output characteristics. In the figure, the variable flux rotating electric machine 1 of the present invention is shown as an example with a solid line. In the figure, the analysis results of an IPM motor are shown as a comparative example with a dashed line. In the example, the output drops at 10,000 rpm, but it was confirmed that the output in the high-speed rotation region of 15,000 rpm or higher is higher compared to the comparative example.

[0075] From the above analysis results, it was confirmed that housing the inverse magnetostrictive member 7 in the housing 6 applies compressive stress that significantly changes its magnetic properties, and that this stress is relieved by centrifugal force, causing a change in permeability. As the compressive stress of the inverse magnetostrictive member 7 is relieved by centrifugal force, the short-circuit magnetic flux in the rotor 2 increases, and it was confirmed that the high-speed operating range is expanded compared to the IPM motor.

[0076] [Second Embodiment] Figure 12 shows a part of another variable flux rotating electric machine 1a to which the present invention is applied. The figure shows a part of the rotor 2a of the variable flux rotating electric machine 1a, and an enlarged cross-sectional view of its main part. The figure shows the part corresponding to Figure 4, which shows the rotor 2 of the variable flux rotating electric machine 1 of the first embodiment.

[0077] The variable flux rotating electric machine 1a shown in Figure 12 is characterized in that a weight 11 with a density greater than that of the reverse magnetostrictive member 7a is housed in the housing 6. Except for the fact that the reverse magnetostrictive member 7a and the weight 11 are housed in the housing 6, the configuration is the same as that of the variable flux rotating electric machine 1 of the first embodiment already described, so a description of the configuration that is the same as that already described will be omitted.

[0078] As shown in the figure, the rotor 2a of the variable flux rotating electric machine 1a has a rotor core 4, a plurality of permanent magnets 5, a plurality of housings 6, a plurality of inverse magnetostrictive members 7a, and a plurality of weights 11. The inverse magnetostrictive members 7a are made of the same material as the inverse magnetostrictive member 7 described in the first embodiment.

[0079] The reverse magnetostrictive member 7a is provided with a compression space as shown by the dashed line in the figure, and the reverse magnetostrictive member 7a is housed in the housing 6 with this compression space compressed. When the compression space is compressed, the reverse magnetostrictive member 7a is pressurized from the weight 11 and the inner wall of the housing 6. The reverse magnetostrictive member 7a is housed, for example, by being press-fitted into the housing 6 where the weight 11 is placed.

[0080] It is preferable that the weight 11 moves outward easily along with the outward deformation of the outer wall 8, so that the compressive stress on the reverse magnetostrictive member 7a decreases when the outer wall 8 deforms outward. For this reason, it is preferable that the weight 11 does not have a clamping allowance.

[0081] In this second embodiment, since the density of the weight 11 is greater than the density of the inverse magnetostrictive member 7a, the combined weight of the weight 11 and the inverse magnetostrictive member 7a housed in the housing 6 is greater than the weight of the inverse magnetostrictive member 7 housed in the housing 6 in the first embodiment. As a result, the centrifugal force acting on the outer periphery wall 8 during rotation is increased, making the outer periphery wall 8 more susceptible to deformation.

[0082] It is preferable to place the weight 11 on the outer circumference of the housing 6 rather than the inverse magnetostrictive member 7a, because the centrifugal force generated by the weight 11 will be greater, making the outer wall 8 more easily deformable.

[0083] If direct contact between the reverse magnetostrictive member 7a and the outer peripheral wall 8 results in a greater change in compressive stress on the reverse magnetostrictive member 7a, the reverse magnetostrictive member 7a may be placed on the outer peripheral side (outer peripheral wall 8 side) of the housing 6, and the weight 11 may be placed on the inner peripheral side. The shape and placement of the weight 11 are arbitrary.

[0084] In the second embodiment of the variable flux rotating electric machine 1a, similar to the first embodiment, when the rotor 2a rotates at high speed, the outer peripheral wall 8 deforms outward due to centrifugal force, reducing the compressive stress on the reverse magnetostrictive member 7a and increasing the permeability of the reverse magnetostrictive member 7a. As a result, the magnetic flux that short-circuits within the rotor 2a through the reverse magnetostrictive member 7a increases at high rotational speeds.

[0085] [Third Embodiment] Figure 13 shows a part of yet another variable flux rotating electric machine 1b to which the present invention is applied. The figure shows a part of the rotor 2b of the variable flux rotating electric machine 1b, and an enlarged cross-sectional view of its main part. This figure corresponds to the part shown in Figure 4, which shows the rotor 2 of the variable flux rotating electric machine 1 of the first embodiment.

[0086] The variable flux rotating electric machine 1b shown in Figure 13 is characterized by the placement of a sheet-like member 12, which has elasticity in a compressed state, between the reverse magnetostrictive member 7b and the inner wall of the housing 6. Except for the fact that the reverse magnetostrictive member 7b and the sheet-like member 12 are housed in the housing 6, the configuration is the same as that of the variable flux rotating electric machine 1 of the first embodiment already described, so the description of the same configuration as already described will be omitted.

[0087] As shown in the figure, the rotor 2b of the variable flux rotating electric machine 1b has a rotor core 4, a plurality of permanent magnets 5, a plurality of housings 6, a plurality of inverse magnetostrictive members 7b, and a plurality of sheet-like members 12. The inverse magnetostrictive members 7b are made of the same material as the inverse magnetostrictive member 7 described in the first embodiment. No interference fit is formed on the inverse magnetostrictive members 7b.

[0088] As shown in the figure, the inverse magnetostrictive member 7b is surrounded by a sheet-like (layered) sheet-like member 12. The sheet-like member 12 is elastic and is made of an elastic material such as metal or resin. Preferably, the sheet-like member 12 is made of a material that is more elastically deformable than the inverse magnetostrictive member 7b. For example, the sheet-like member 12 is made of a material with a smaller Young's modulus than the inverse magnetostrictive member 7b. Because the sheet-like member 12 is compressed, the inverse magnetostrictive member 7b is housed in the housing 6 under pressure from the sheet-like member 12.

[0089] The reverse magnetostrictive member 7b is housed in the housing section 6 by press-fitting it together with the sheet-like member 12, for example. Alternatively, the reverse magnetostrictive member 7b is housed in the housing section 6 by press-fitting the sheet-like member 12 first, and then press-fitting the reverse magnetostrictive member 7b into the housing section 6.

[0090] The sheet-like member 12 is preferably made of a material with high magnetic permeability so that magnetic flux can pass through easily (so as not to become a flux barrier). Examples of materials for the sheet-like member 12 include a resin containing magnetic powder or a soft magnetic metal.

[0091] Magnetic powder is a soft magnetic material formed into a powder (fine particle) form. Examples of materials for magnetic powder include Sendust, iron-based amorphous materials, and permalloy. Materials with high magnetic permeability and low iron loss are preferably used for magnetic powder. Sendust, in particular, which has high magnetic permeability and low iron loss, is preferably used. Multiple types of magnetic powder may be blended. Magnetic powder may also be coated with an insulating material.

[0092] There are no limitations on the size of the magnetic powder, but smaller sizes are preferable because they reduce iron loss. A preferred size for magnetic powder is, for example, a maximum particle size of 20 μm to 70 μm.

[0093] There are no limitations on the material of the resin; for example, an elastic 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 properties. Examples of thermoplastic resins include acrylic resin, polytetrafluoroethylene, polyamide, polyacetal, ABS resin, and AS resin.

[0094] Examples of elastic soft magnetic metals include iron-based metals, amorphous alloys, and permendur.

[0095] In the third embodiment of the variable flux rotating electric machine 1b, when the rotor 2b rotates at high speed, the centrifugal force deforms the outer peripheral wall 8 outward, expanding the area of ​​the housing 6. This reduces the compressive stress from the sheet-like member 12 on the inverse magnetostrictive member 7b, and increases the permeability of the inverse magnetostrictive member 7b. As a result, the magnetic flux that short-circuits within the rotor 2b through the inverse magnetostrictive member 7b increases at high rotational speeds.

[0096] [Fourth Embodiment] Figure 14 shows a part of yet another variable flux rotating electric machine 1c to which the present invention is applied. The figure shows a part of the rotor 2c of the variable flux rotating electric machine 1c, and an enlarged cross-sectional view of its main parts. The enlarged cross-sectional view in the figure shows, in particular, the structure of the outer periphery wall 8c.

[0097] The variable flux rotating electric machine 1c shown in Figure 14 is characterized in that the outer peripheral wall 8c of the housing 6c is formed separately from the rotor core 4c. The variable flux rotating electric machine 1c is configured the same as the variable flux rotating electric machine 1 of the first embodiment already described, except that the outer peripheral wall 8c of the housing 6c is separate from the rotor core 4c, so the configuration which is the same as that already described will not be explained.

[0098] In the first to third embodiments described above (variable magnetic flux type rotating electric machines 1 to 1b), the outer peripheral wall 8 was the outer periphery of the rotor core 4 and was therefore formed integrally with the rotor core 4. In other words, the outer peripheral wall 8 was part of the rotor core 4.

[0099] As shown in the figure, the rotor 2c of the variable flux rotating electric machine 1c has a rotor core 4c, a plurality of permanent magnets 5, a plurality of housings 6c, a plurality of reverse magnetostrictive members 7, and an outer wall member 15.

[0100] The housing section 6c is a region formed between adjacent permanent magnets 5, where there are no rotor cores 4c. The outer periphery of the housing section 6c is open to the outside, as there are no rotor cores 4c there. The rotor core 4c is surrounded by an outer wall member 15 with an annular cross-section. The outer wall member 15 on the outer periphery of the housing section 6c forms the outer wall 8c of the housing section 6c. This outer wall 8c closes the housing section 6c in a room-like manner.

[0101] The reverse magnetostrictive member 7 is provided with a clamping allowance, similar to the first embodiment. The reverse magnetostrictive member 7 is housed in the housing section 6c under pressure as the clamping allowance is compressed. The outer wall member 15 (outer peripheral wall 8c) is configured to be able to pressurize the reverse magnetostrictive member 7 without deforming at low rotation speeds, and to deform outward due to centrifugal force at high rotation speeds, thereby reducing the compressive stress on the reverse magnetostrictive member 7.

[0102] The reverse magnetostrictive member 7 is housed in the housing section 6c by press-fitting it into the housing section 6c after fitting the outer wall member 15 onto the outer circumference of the rotor core 4c, for example. Alternatively, the reverse magnetostrictive member 7b may be placed in the housing section 6 of the rotor core 4c before fitting the outer wall member 15, and then the outer wall member 15 may be fitted onto the outer circumference of the rotor core 4c. The outer wall member 15 may be fixed to the rotor core 4c by fixing means (e.g., screwing, fitting with the rotor core 4c, etc.).

[0103] There are no limitations on the material of the exterior wall component 15, but examples include electrical steel sheets, ferrous metals, aluminum, amorphous alloys, and Permendur.

[0104] Thus, when the outer perimeter wall 8c is formed separately from the rotor core 4c, the ease of deformation and the magnitude of displacement of the outer perimeter wall 8c can be appropriately set by the material and thickness used for the outer perimeter wall 8c.

[0105] In the variable flux rotating electric machine 1c of the fourth embodiment, when the rotor 2c rotates at high speed, the outer peripheral wall 8c deforms outward due to centrifugal force, expanding the area of ​​the housing 6c. This reduces the compressive stress from the outer peripheral wall 8c on the reverse magnetostrictive member 7, and increases the permeability of the reverse magnetostrictive member 7. As a result, the magnetic flux that short-circuits within the rotor 2c through the reverse magnetostrictive member 7 increases at high rotational speeds.

[0106] Although an example has been described in which a single ring-shaped outer wall member 15 is arranged, it is also possible to form multiple outer wall members divided according to the number of poles (6 poles in this example) and arrange an outer wall member for each housing section 6c. For example, each outer wall member 15 (outer wall 8c) may be fixed to the rotor core 4c by fixing means (e.g., screwing, fitting with the rotor core 4c) on the outer circumference side of each housing section 6c. [Explanation of symbols]

[0107] 1·1a·1b·1c are variable flux rotating electric machines, 2·2a·2b·2c are rotors, 3 is a stator, 4·4c are rotor cores, 5 is a permanent magnet, 6·6c are housings, 7·7a·7b are reverse magnetostrictive members, 8·8c are outer walls, 11 is a weight, 12 is a sheet-like member, 15 is an outer wall member, 31 is a stator core, 32 is a tooth, 33 is a slot, 34 is a stator winding, 41 is a rotating shaft, 42 is a shaft fixing member, and D1·D2·D3·D4 are clamping allowances.

Claims

1. A variable flux rotating electric machine comprising a rotor and a stator that generates a rotating magnetic field for the rotor, The rotor comprises a rotor core made of a soft magnetic material, a plurality of permanent magnets embedded inside the rotor core so as to alternately change polarity along the circumferential direction of the rotor core, a housing portion which is a region without the rotor core formed between adjacent permanent magnets, and an inverse magnetostrictive member housed in the housing portion under pressure. The aforementioned inverse magnetostrictive member has a permeability that changes such that the permeability decreases as the applied pressure increases and increases as the pressure decreases. The housing has an outer peripheral wall that closes the outer peripheral side of the rotor, A variable flux rotating electric machine characterized in that the outer peripheral wall is formed to be deformable outward when the rotor rotates at high speed compared to when it rotates at low speed, and the pressure pressing on the reverse magnetostrictive member can be changed by the deformation of the outer peripheral wall.

2. The variable magnetic flux type rotating electric machine according to claim 1, characterized in that the reverse magnetostrictive member is provided with a clamping allowance, and the reverse magnetostrictive member is housed in the housing portion with the clamping allowance compressed.

3. The variable magnetic flux type rotating electric machine according to claim 1, characterized in that a sheet-like member having elasticity in a compressed state is arranged between the inverse magnetostrictive member and the inner wall of the housing.

4. The variable magnetic flux rotating electric machine according to any one of claims 1 to 3, characterized in that when the inverse magnetostrictive member is represented in a cross-section perpendicular to the rotation axis of the rotor, the width along the circumferential direction of the rotor core is wider on the outer circumference side than on the inner circumference side.

5. The variable magnetic flux rotating electric machine according to claim 4, characterized in that the inverse magnetostrictive member is formed in a substantially trapezoidal shape with its upper and lower bases each formed by straight lines or curves, and is arranged with the shorter upper base on the inner circumference side and the longer lower base on the outer circumference side of the rotor core.

6. The variable flux rotating electric machine according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed with a constant thickness.

7. The variable flux rotating electric machine according to any one of claims 1 to 3, characterized in that the inverse magnetostrictive member is formed with a density greater than that of the rotor core.

8. The variable flux type rotating electric machine according to any one of claims 1 to 3, characterized in that a weight with a density greater than that of the inverse magnetostrictive member is housed in the housing section.

9. The variable flux rotating electric machine according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed by the rotor core.

10. The variable flux rotating electric machine according to any one of claims 1 to 3, characterized in that the outer peripheral wall is formed separately from the rotor core.

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