JP2021151142A - Permanent magnet rotor and rotary electric machine - Google Patents

Abstract

To provide a permanent magnet rotor capable of suppressing an irreversible demagnetization in a structure where an arc-shaped permanent magnet is arranged in a multi layer, and provide a rotary electric machine having such as a permanent magnet rotor.SOLUTION: A permanent magnet rotor 10 has a rotor core 11; and a plurality of permanent magnets 15 and 16 embedded into the rotor core 11 and structuring a magnetic pole. In a cross section orthogonal to a rotational axis R of the rotor core 11, the plurality of permanent magnets 15 and 16 include a convexed arc shape toward an inner peripheral side of each rotor core 11, is arranged in two or more layers toward the inner peripheral side from an outer peripheral side of the rotor core 11. Each of thicknesses Lm1 and Lm2 of the permanent magnets 15 and 16 are larger than that of the permanent magnet 16 arranged on the inner peripheral side of the rotor core 11, and a difference of a permeance coefficient of the optional two permanent magnets 15 and 16, which are adjacent to a radial direction of the rotor core 11 is 15% or less of an average value of the permeance coefficient of the two permanent magnets 15 and 16.SELECTED DRAWING: Figure 2

Description

The present invention relates to a permanent magnet rotor and a rotating electric machine, and more particularly to a permanent magnet rotor in which a permanent magnet is embedded in a rotor core, and a rotating electric machine having such a permanent magnet rotor.

Rotating electric machines using permanent magnet rotors, such as permanent magnet embedded (IPM) motors, are being developed with the aim of increasing efficiency and miniaturization. The inventors are also developing a structure capable of increasing efficiency and miniaturization in a permanent magnet rotor in which an arc-shaped permanent magnet is embedded in a rotor core in multiple layers as in Patent Documents 1 to 4. ..

Japanese Unexamined Patent Publication No. 2019-187197 Japanese Unexamined Patent Publication No. 2019-187198 JP-A-2019-187199 Japanese Unexamined Patent Publication No. 2019-187200

In a rotating electric machine having a permanent magnet rotor, one of the factors that determines the performance limit is the irreversible demagnetization of the permanent magnet. For example, the magnetic field generated by the coil of the stator is applied to the permanent magnet in the direction opposite to the magnetization direction of the permanent magnet and acts as a reverse magnetic field, which may cause irreversible demagnetization of the permanent magnet. In addition, heat generated during operation of the rotating electric machine may also cause irreversible demagnetization of the permanent magnet.

In the permanent magnet rotor, one of the methods for suppressing the irreversible demagnetization of the permanent magnet is to use a material having a high coercive force, including a material containing a large amount of heavy rare earths such as Tb and Dy as a component of the permanent magnet. Can be mentioned. Further, by increasing the thickness of the permanent magnet, the influence of the reverse magnetic field on the permanent magnet can be reduced, and the irreversible demagnetization can be reduced. However, from the viewpoint of avoiding the high price of the rotating electric machine, it is preferable to keep the content of heavy rare earths in the permanent magnet as low as possible. Further, it is preferable that the amount of permanent magnets used is small.

Therefore, it is necessary to develop a permanent magnet rotor and a rotating electric machine that can suppress irreversible demagnetization by examining the shape and arrangement of the permanent magnets without relying on increasing the coercive magnetic force of the permanent magnets or increasing the amount used. Is desired. In the permanent magnet rotor, when the arc-shaped permanent magnets are arranged in multiple layers, the influence of the reverse magnetic field from the coil of the stator differs for each layer, and the entire permanent magnet rotor including the permanent magnets of multiple layers Therefore, it is important to develop a structure having high resistance to irreversible demagnetization.

The problem to be solved by the present invention is a permanent magnet rotor capable of suppressing irreversible demagnetization in a structure in which arc-shaped permanent magnets are arranged in multiple layers, and a rotating electric machine having such a permanent magnet rotor. To provide the machine.

In order to solve the above problems, the permanent magnet rotor according to the present invention is a permanent magnet rotor having a rotor core and a plurality of permanent magnets embedded in the rotor core and forming magnetic poles, and the rotation of the rotor core. In the cross section orthogonal to the axis, the plurality of permanent magnets each have a convex arc shape toward the inner peripheral side of the rotor core, and have two or more layers from the outer peripheral side to the inner peripheral side of the rotor core. The permanent magnets are thicker than the permanent magnets arranged on the inner peripheral side of the rotor core, and the permence of any two permanent magnets adjacent to each other in the radial direction of the rotor core. The difference between the coefficients is 15% or less of the average value of the permence coefficients of the two permanent magnets.

Here, the plurality of permanent magnets may be arranged in two layers, an outer magnet and an inner magnet, from the outer peripheral side to the inner peripheral side of the rotor core.

The plurality of permanent magnets are arranged in two layers of an outer magnet and an inner magnet from the outer peripheral side to the inner peripheral side of the rotor core, and the opening angle of the inner magnet is θ _M2 in terms of electric angle, and θ _opt −5 ° ≦ θ _M2 ≦ θ _opt + 5 °.
Here, the outer magnet and the thickness of the inner magnet, and each L _m1 and L _{m @ 2,} the average value of the permeance coefficient of the inner magnet and the outer magnet as Pc _a, the theta _opt, the unit of ° As,
^{_{θ opt = 260 (L m1 /}} L m2) 3 -380 (L m1 / L m2) 2 +260 (L m1 / L m2) is ₊ 14.5Pc a _+54.3.

In this case, the opening angle of the outer magnet may be 50 ° ≤ θ _M1 ≤ 120 °, _{where θ M1 is the electrical angle.}

The plurality of permanent magnets may have a concentric arc shape.

The plurality of permanent magnets may be hot plastic working magnets.

The rotating electric machine according to the present invention has the above-mentioned permanent magnet rotor.

In the permanent magnet rotor according to the above invention, a high reluctance torque can be obtained by arranging a plurality of arc-shaped permanent magnets in a layer in a cross section orthogonal to the rotation axis of the rotor core. At the same time, the thickness of the plurality of permanent magnets is thicker as that of the permanent magnets arranged on the inner peripheral side of the rotor core, so that the inner peripheral side tends to cause irreversible demagnetization more than the permanent magnets on the outer peripheral side. It is easy to avoid irreversible demagnetization in the permanent magnets of. Further, the difference in the permeance coefficients of any two permanent magnets adjacent to each other in the radial direction of the rotor core is suppressed to 15% or less of the average value of the permeance coefficients of those permanent magnets. As an effect, in some of these permanent magnets, irreversible demagnetization is less likely to occur due to the extremely small permence coefficient of many parts, and the magnetic force of the permanent magnet rotor as a whole is maintained. High resistance to irreversible demagnetization can be obtained. As a result, it is possible to obtain a permanent magnet rotor that is less likely to cause irreversible demagnetization and can maintain magnetic force while suppressing the content of heavy rare earth in the permanent magnet and the amount of the permanent magnet used to be small.

Here, when a plurality of permanent magnets are arranged in two layers of an outer magnet and an inner magnet from the outer peripheral side to the inner peripheral side of the rotor core, the permanent magnets are simply provided in only two layers. In the configuration, the irreversible demagnetization of these two layers of permanent magnets can be effectively suppressed.

A plurality of permanent magnets are arranged in two layers, an outer magnet and an inner magnet, from the outer peripheral side to the inner peripheral side of the rotor core, and the opening angle of the inner magnet is θ _M2 in terms of electric angle, and θ _opt- 5. When ° ≤ θ _M2 ≤ θ _opt + 5 °, the difference in the permence coefficient between the outer magnet and the inner magnet is suppressed to a small value, and the permanent magnet rotor as a whole suppresses irreversible demagnetization, with respect to irreversible demagnetization. It can exert high resistance. The _{opening angle θ M2 where θ opt} is the smallest difference between the permeance coefficients of these two permanent magnets according to the ratio _{of the thickness L m1} of the outer magnet and the thickness L _{m2 of the inner magnet (L m1} / L _m2). This is because it indicates the optimum value of. For the optimum value θ _opt , parameters such as the material and total thickness of the two permanent magnets and the magnitude of the reverse magnetic field from the stator coil can be taken into consideration as the average value of the permeance coefficients of the two permanent magnets. can.

In this case, if the opening angle of the outer magnet is θ _M1 in terms of electric angle and 50 ° ≤ θ _M1 ≤ 120 °, the harmonic component of the magnetic flux density distribution formed on the outside of the permanent magnet rotor is reduced. At the same time, it is possible to obtain a high effect of improving the reluctance torque by arranging the permanent magnets in two layers. The permanent magnet rotor has these characteristics together with the effect of suppressing irreversible demagnetization by setting _{the opening angle θ M2 of the inner magnet as described above.}

When the plurality of permanent magnets have concentric arcuate shapes, a permanent magnet rotor having a relatively simple shape and arrangement is used to effectively suppress irreversible demagnetization. Obtainable.

When the plurality of permanent magnets are hot-plasticized magnets, the hot-plasticized magnets can easily form an arc-shaped permanent magnet, and the magnetization direction can be easily set to the radial direction, so that the plurality of arcs can be formed. Permanent magnets of a shape can be suitably used for forming a permanent magnet rotor in which the permanent magnets are arranged in layers.

Since the rotating electric machine according to the above invention has the above-mentioned permanent magnet rotor, irreversible demagnetization of the permanent magnet in the permanent magnet rotor can be effectively suppressed.

It is sectional drawing which shows the structure of the permanent magnet rotor and the rotating electric machine which concerns on one Embodiment of this invention. It is sectional drawing which extracted the part of the permanent magnet rotor which concerns on one Embodiment of this invention. Corresponds to the enlarged view of FIG. It is a figure which shows the distribution of the permeance coefficient in a permanent magnet in the case of L _m1 = 0.9 mm, L _m2 = 2.1 mm, θ _{M1 = 59.5 °.} (A) shows _{the case of θ M2} = 99.5 °, and (b) shows the case of _{θ M2 = 135.4 °.} It is a figure which shows the change of the permeance coefficient when the opening angle θ _M1 and the opening angle θ _M2 are changed in the case of L _m1 = 0.9 mm and L _{m2 = 2.1 mm.} It is a figure which shows the change of the permeance coefficient when the opening angle θ _M1 and the opening angle θ _M2 are changed in the case of L _m1 = 1.2 mm and L _{m2 = 1.8 mm.} It is a figure which shows the change of the permeance coefficient when the opening angle θ _M1 and the opening angle θ _M2 are changed in the case of L _m1 = 1.5 mm and L _{m2 = 1.5 mm.} It is a figure which plotted the optimum value of the opening angle θ _{M2 as a function of a thickness ratio L m2} / L _m1. The results are shown for each case where the magnitude of the reverse magnetic field is changed. It is a figure which plotted the value of the permeance coefficient corresponding to the optimum value of the opening angle θ _{M2 as a function of the thickness ratio L m2} / L _m1. The results are shown for each case where the magnitude of the reverse magnetic field is changed. It is a figure which plotted the optimum value of the opening angle θ _{M2 as a function of a thickness ratio L m1} / L _m2. The results are shown for each case where the magnitude of the inverse magnetic field is changed, and for the case where the magnitude of the inverse magnetic field is 100%, a curve based on an approximate expression that approximates the plot points with a cubic function is also shown. There is. It is a figure which shows the relationship between the permeance coefficient and the intercept value in the approximate expression about the case where the magnitude of a reverse magnetic field is changed. It is a figure which shows the behavior of the permeance coefficient when the total thickness of two layers of permanent magnets is changed. (A) is L _m1 = 0.6 mm, L _m2 = 1.4 mm, (b) is L _m1 = 0.8 mm, L _m2 = 1.2 mm, (c) is L _m1 = 1.8 mm, L _m2 = The case of 2.7 mm is shown. It is the figure which plotted _{the inclination of the opening angle θ M2} with respect to the permeance coefficient of an inner magnet _{as a function of the thickness ratio L m1} / L _m2. (A) shows _{the case where the opening angle θ M1} is about 60 °, and (b) shows the case where the _{opening angle θ M1 is about 75 °.}

Hereinafter, the permanent magnet rotor and the rotating electric machine according to the embodiment of the present invention will be described in detail with reference to the drawings. In this specification, the notation of the angle is based on the electric angle (°).

[Structure of rotating electric machine]
The outline of the rotary electric machine 1 according to the embodiment of the present invention is shown in FIG. 1 in a cross-sectional view orthogonal to the rotation axis. The rotating electric machine 1 has a permanent magnet rotor 10 according to an embodiment of the present invention. In this specification, the case where the rotary electric machine 1 is a motor will be mainly described, but the same configuration can be applied to the case where the rotary electric machine 1 is a generator.

The rotary electric machine 1 is configured as a permanent magnet embedded (IPM) motor. The motor 1 has a hollow cylindrical stator (stator) 30 and a rotor (permanent magnet rotor) 10 coaxially and axially rotatably supported in the hollow portion of the stator 30.

The stator 30 has a stator core 31 and a coil (not shown). The stator core 31 is formed by laminating a plurality of layers of electromagnetic steel plates, and integrally integrates a ring-shaped back yoke portion 31a and a plurality of teeth 31b protruding inward from the back yoke portion 31a. Be prepared for. A coil is wound around the outer circumference of each tooth 31b.

The rotor 10 has a rotor core 11 having a substantially columnar outer shape, and a plurality of permanent magnets M embedded in the rotor core 11. A hollow portion is formed in the center of the rotor core 11, and the shaft 40 is inserted therethrough. An air gap 50 is secured between the teeth 31b of the stator core 31 and the outer peripheral surface of the rotor core 11 in a state where the rotor 10 is coaxially housed in the hollow portion of the stator 30. The details of the configuration of the rotor 10 will be described below.

[Outline of the configuration of the permanent magnet rotor]
As described above, the rotor (permanent magnet rotor) 10 has a rotor core 11 and a plurality of permanent magnets M. The configuration of the rotor 10 is shown in FIGS. 1 and 2. FIG. 2 shows one magnetic pole of the rotor 10, and a plurality of (here, four) magnetic poles are continuously arranged rotationally symmetrically while alternately changing the polarity of the permanent magnet M for each magnetic pole. This is the overall structure of the rotor 10 as shown in FIG. In the following, terms indicating the direction in the rotating body, such as "diameter direction", "outer circumference", "inner circumference", "outer side", and "inner side", refer to the direction of the rotor core 11 unless otherwise specified. do.

The rotor core 11 is formed by laminating a plurality of electromagnetic steel sheets, and has a substantially cylindrical outer peripheral surface. A plurality of slots S are formed in the rotor core 11 as voids penetrating or sinking in the axial direction. The slot S has an arc shape that is convex toward the inner peripheral side (inward in the radial direction) of the rotor core 11. The specific shape of the slot S is not particularly limited, but here, each slot S has a substantially arc shape. That is, in each slot S, the inner peripheral side edge located on the inner peripheral side of the rotor core 11 and the outer peripheral side edge located on the outer peripheral side of the rotor core 11 are formed as arcs convex toward the inside of the rotor core 11, respectively. It is formed.

A permanent magnet M is embedded in each slot S. Corresponding to the slot S having a substantially arc shape, the permanent magnet M also has a substantially arc shape. The permanent magnet M occupies substantially the entire area of the slot S in the thickness direction connecting the outer peripheral side edge and the inner peripheral side edge of the slot S. The length of the region occupied by the permanent magnet M in the longitudinal direction (direction along the arc shape) of the slot S is not particularly limited, and may be appropriately selected according to required characteristics such as output. The permanent magnet M embedded in each slot S may be divided into a plurality of parts. In the illustrated form, the permanent magnet 16 embedded in the inner slot 14 is divided into two parts.

The permanent magnets M embedded in the slot S and the slot S have two or more layers from the outer peripheral side (diameter outer side) to the inner peripheral side (diameter inner side) of the rotor core 11 from the viewpoint of improving the reluctance torque. Have been placed. As long as there are two or more layers, the specific number and arrangement of the layers is not particularly limited, but in the present embodiment, the number of layers is two from the viewpoint of simplification of the structure and the like. That is, from the outer peripheral side to the inner peripheral side of the rotor core 11, two layers of an outer slot 13 in which the outer magnet 15 is embedded and an inner slot 14 in which the inner magnet 16 is embedded are arranged. Moreover, they are arranged in a concentric arc shape.

As will be described in detail later, in the present embodiment, the relationship between _{the thickness L m1 of the outer magnet 15 and the thickness L m2} of the inner magnet 16 is specified. Further, suitable ranges are set as _{the opening angle θ M1} of the outer magnet 15 and the opening angle θ _{M2 of the inner magnet 16.} The thickness of each of the permanent magnets 15 and 16 refers to the distance between the outer peripheral side edge and the inner peripheral side edge of the permanent magnets 15 and 16. Further, the opening angles θ _M1 and θ _M2 of the permanent magnets 15 and 16 are the angles formed by both ends of the peripheral edges of the permanent magnets 15 and 16 in the longitudinal direction with respect to the rotation center R of the rotor core 11. Point to.

The magnetization direction of each permanent magnet M is not particularly limited, but is preferably a radial direction centered on the arc-shaped focal point. The type of permanent magnet M is not particularly limited, but is preferably a metal magnet. That is, it is preferable that the material is made of only a metal magnet material without containing a metal oxide or an organic compound intentionally added except in the vicinity of the surface. Further, it is preferably a hot plastically worked magnet composed of microcrystal grains of a metal magnet material. The hot plastic working magnet can be formed into an arc shape and magnetized in the radial direction relatively easily.

In the present embodiment, irreversible demagnetization is suppressed by defining the relationship between the thickness and the permeance coefficient among the plurality of permanent magnets M. If the wall thickness of the permanent magnet is thin, demagnetization is relatively likely to occur. However, in the present embodiment, by defining the relationship between the thickness of the permanent magnet M as follows, even if the permanent magnet M is relatively thin. , It is possible to effectively suppress demagnetization. Hereinafter, the relationship between the thickness of the permanent magnet M and the permeance coefficient, and the effects produced by them will be described in detail with reference mainly to FIG.

[Permanent magnet thickness and permeance coefficient]
In the present embodiment, as described above, the arc-shaped permanent magnets M are arranged in a plurality of layers, preferably two layers, from the outer peripheral side to the inner peripheral side along the radial direction of the rotor core 11. The thickness of the permanent magnets M arranged in these layers is thicker than that of the permanent magnets M arranged on the inner peripheral side of the rotor core 11. That is, when the number of layers of the permanent magnet M is two, _{the thickness L m2} of the inner magnet 16 is larger than _{the thickness L m1} of the outer magnet 15 (L _m1 <L _m2). ).

When the rotor 10 is rotated to operate the motor 1, heat is generated, and the heat generation may cause an irreversible demagnetization portion (a portion where irreversible demagnetization has occurred) in the permanent magnet M. Further, the magnetic field from the coil provided on the stator 30 is applied to the permanent magnet M in the direction opposite to the magnetization direction of the permanent magnet M and acts as a reverse magnetic field, which may cause an irreversible demagnetization portion. There is. The reverse magnetic field from the coil of the stator 30 is only the magnetic field from the coils installed on a small number of teeth 31b located in front of the outer peripheral side at the position of the permanent magnet M (outer magnet 15) located on the outer peripheral side. On the other hand, at the positions of the permanent magnets M (inner magnets 16) located on the inner peripheral side, not only the teeth 31b located on the front surface on the outer peripheral side but also a plurality of permanent magnets M (inner magnets 16) located in a wide range on both sides along the circumferential direction. The magnetic fields from the coils installed in the teeth 31b of the above are combined to form a reverse magnetic field. Therefore, the permanent magnet M (inner magnet 16) on the inner peripheral side is more susceptible to the influence of the reverse magnetic field. However, in the arc-shaped permanent magnet M, the larger the thickness, the less likely it is that irreversible demagnetization will occur due to the application of a reverse magnetic field. Therefore, if the thickness of the permanent magnet M (inner magnet 16) on the inner peripheral side is increased, the irreversible demagnetization of the permanent magnet M can be suppressed to be small as the entire rotor 10.

In each permanent magnet M, the specific degree of irreversible demagnetization depends on the permeance coefficient, and the larger the permeance coefficient, the less irreversible demagnetization is likely to occur. Irreversible demagnetization occurs with each crystal exhibiting magnetization (magnetic moment) as the smallest unit. Therefore, the permeance coefficient in the permanent magnet correlates with the inverse magnetic field in each crystal and is distributed in the permanent magnet. Here, the crystal in which irreversible demagnetization is generated loses magnetization, and the magnetic flux generated in the permanent magnet decreases in correlation with the volume in which irreversible demagnetization occurs in the permanent magnet. Thus, the magnitude of the permence coefficient and the likelihood of irreversible demagnetization have a spatial distribution within one permanent magnet (see FIG. 3), but in the present specification, unless otherwise specified, the permence coefficient is It shall refer to the average value in the entire area of one permanent magnet M, and the susceptibility to irreversible demagnetization shall also be referred to from the viewpoint of the average tendency of one permanent magnet M. Regarding the torque / output performance, which is an important performance of the motor, the higher the performance is, the less irreversible demagnetization occurs in the average behavior of each permanent magnet M as a whole.

When the rotor 10 is provided with a plurality of permanent magnets M having different environments, the closer the values of the permence coefficients of the permanent magnets M are and the smaller the difference between the values, the more a part of the plurality of permanent magnets M. In the permanent magnet M of the above, as compared with other permanent magnets M, it is possible to avoid a situation in which the number of irreversible demagnetization occurrence sites becomes extremely large, and the influence of the irreversible demagnetization can be suppressed low as a whole of the rotor 10. Therefore, in the rotor 10, it is preferable to make the difference in permeance coefficient as small as possible among the plurality of permanent magnets M arranged in layers along the radial direction of the rotor core 11.

Specifically, in a set of two permanent magnets M adjacent to each other along the radial direction of the rotor core 11, the permeance coefficient of the two permanent magnets is relative to the average of the permeance coefficients of the two permanent magnets M. The difference may be set to be equal to or less than a predetermined upper limit value A. As the upper limit value A, a value of 15% and further 8% can be mentioned. Here, in a set of two adjacent permanent magnets M, the difference in permeance coefficient is equal to or less than a predetermined upper limit value A. Even if the set of magnets M is taken, it means that the difference between the two permeance coefficients is equal to or less than a predetermined upper limit value. When the permanent magnets M are provided in two layers, the permeance coefficient of the outer magnet 15 is Pc ₁ and the permeance coefficient of the inner magnet 16 is Pc ₂ , and the difference between them is as shown in the following equation 1 with respect to the average value. Therefore, the upper limit value A or less may be set.
| Pc _{1- Pc 2} | / {(Pc ₁ + Pc ₂ ) / 2} x 100% ≤ A (1)

Alternatively, the value of the difference between the permeance coefficients of the two permanent magnets 15 and 16, that is, | Pc _{1 − Pc 2} | may be set to be equal to or less than a predetermined upper limit value B. The specific value of the upper limit value B _{depends on the size of the permeance coefficients Pc 1} and Pc ₂ of the two permanent magnets 15 and 16, but for example, the average value of the permeance coefficients Pc ₁ and Pc _{2 is 0.} When it is 6 or more and 0.8 or less, a value of 0.1 can be given as the upper limit value B of the difference. _{The magnitudes of the permeance coefficients Pc 1} and Pc ₂ of the two permanent magnets 15 and 16 are preferably about 0.3 or more, more preferably 0.4 or more on average.

In the arc-shaped permanent magnet M, the permeance coefficient depends not only on the material of the permanent magnet M but also on the specific shape, dimensions, and arrangement determined by the thickness and the opening angle. Therefore, in the rotor 10 in which a plurality of permanent magnets M are arranged in layers in the radial direction of the rotor core 11, the ratio of the difference between the permanent magnets M adjacent in the radial direction to the average of the permeance coefficients is equal to or less than the upper limit value A. The shape, size, and arrangement of each permanent magnet M may be set so as to be as small as possible. As described above, if the thickness of the permanent magnet M (inner magnet 16) arranged on the inner peripheral side is made larger, the permanent magnet M (outer magnet 15) on the outer peripheral side may be thicker, or each of them. The difference in permence coefficient between adjacent permanent magnets M can be reduced as compared with the case where the permanent magnets M have the same thickness.

Each permanent magnet M is formed thick by reducing the difference in permeance coefficient among the plurality of permanent magnets M embedded in the rotor 10 and suppressing the volume at which irreversible demagnetization occurs in each permanent magnet M. The need can be reduced. Then, the total amount of the permanent magnets M used for the rotor 10 can be suppressed to a small value. Further, permanent magnets containing a large amount of heavy rare earth elements such as Dy and Tb have a high coercive force and are unlikely to cause irreversible demagnetization. In the permanent magnet M, the volume at which irreversible demagnetization occurs can be suppressed to a small size, and irreversible demagnetization can be suppressed in the permanent magnet M as a whole. While suppressing the total amount of permanent magnets M used in the rotor 10 and the content of heavy rare earths to a small extent, irreversible demagnetization is suppressed, and the motor 1 can be operated at an operating point above the knick point.

Since the value of the permit coefficient of each permanent magnet M is determined by the configuration (shape, size, arrangement) of the permanent magnet M, other than increasing the thickness of the permanent magnet M (inner magnet 16) on the inner peripheral side, By examining the specific configuration of each permanent magnet M, the difference in the permence coefficient between the permanent magnets M can be reduced. The specific configuration of the permanent magnet M can be examined, for example, by a simulation using electromagnetic field analysis. For a specific configuration of the permanent magnet M, the permeance coefficient is estimated by simulation, and the difference between the permeance coefficients between layers is set to be equal to or less than the above upper limit value A or minimized with respect to the average value. , The configuration of the permanent magnet M may be selected. At this time, by paying attention to the relationship between the thicknesses of the permanent magnets M and the opening angle of each permanent magnet M and examining the configuration of the permanent magnets M, the difference in the permeance coefficient can be efficiently reduced. Can be searched. Hereinafter, as an example, when the permanent magnets M are provided in two layers, the relationship between the thicknesses of the suitable permanent magnets M and the opening angle will be described.

[Preferable configuration when the permanent magnet has two layers]
When the permanent magnet M is arranged in two layers of the outer magnet 15 and the inner magnet 16, in order to reduce the difference in the permeance coefficient between them, as described above, the thickness of the inner magnet 16 is L _{m2. May} be larger than the thickness L m1 of the outer magnet 15. Further, the permeance coefficient of each of the permanent magnets 15 and 16 is not limited to the thicknesses L _m1 and L _{m2 of the} permanent magnets 15 and 16, but also the opening angles θ _M1 and θ _{M2 of the} permanent magnets 15 and 16, especially the inner magnet 16. It also depends on the opening angle θ _{M2 of.} Generally, as the opening angle θ _M2 of the inner magnet 16 is increased, the permeance coefficient of the outer magnet 15 tends to be smaller, while the permeance coefficient of the inner magnet 16 tends to be larger. _{Then, there is an opening angle θ M2 in} which the permeance coefficients of the outer magnet 15 and the inner magnet 16 showing the opposite tendency with respect to the change in the opening angle θ _{M2 of the inner magnet 16 are equal to each other. The opening angle θ M2} when the permeance coefficients of the two permanent magnets 15 and 16 are equal can be estimated as the optimum opening angle θ _opt.

As shown in a later embodiment, the optimum opening angle θ _opt varies depending on the thickness ratio (thickness ratio; L _m1 / L _m2 ) of the two permanent magnets 15, 16 and the two permanent magnets 15, It can be expressed as a function of a thickness ratio of 16 L _m1 / L _m2. Then, even if the permeance coefficients of the two permanent magnets 15 and 16 are not completely equal, if it is allowed that a difference exists within a predetermined upper limit value between the two permanent magnets, the opening angle θ _M2 is set. A range can be set for the value centered on the optimum opening angle θ _opt.

As derived from the later examples, the optimum opening angle θ _opt can be expressed as the following equation 2 as a function of the thickness ratio L _m1 / L _m2. The unit is the electrical angle (°).
^{_{θ opt = 260 (L m1 /}} L m2) 3 -380 (L m1 / L m2) 2 +260 (L m1 / L m2) + 14.5Pc a +54.3 (2)
Here, Pc _a is an average value of the permeance coefficient _Pc 1, Pc ₂ of the two permanent magnets 15, 16. That is, Pc _a = (Pc ₁ + Pc ₂ ) / 2.

Then, if it is allowed that a difference exists between the values of the permeance coefficients of the two permanent magnets 15 and 16, with the upper limit value being B, the opening angle θ _M2 of the inner magnet 16 is set as in Equation 3. Can be expressed.
θ _opt −C ・ B / 2 ≦ θ _M2 ≦ θ _opt + C ・ B / 2 (3)
Here, C is a constant and corresponds to a constant proportional _{to the opening angle θ M2} with respect to the permeance coefficient of the inner magnet 16 _{(θ M2} = C · Pc ₂ ). As shown in later examples, C = 100 can be set. If B = 0.1, the range of the _{opening angle θ M2 is as follows.}
θ _opt -5 ° ≤ θ _M2 ≤ θ _opt + 5 ° (4)
Further, the difference between the permeance coefficient of the two permanent magnets 15 and 16, as described above, when expressed in the upper limit value A for the ratio of the mean value Pc _a, from equation 3, the opening angle theta _M2 The range can be expressed as in Equation 5 below.
_{θ opt -C · A · Pc a} / 2 ≦ θ M2 ≦ θ opt + C · A · Pc a / 2 (5)

The optimum opening angle θ _{opt is determined by the above equation 2 as a function of the ratio L m1} / L _m2 of the thicknesses of the two permanent magnets 15 and 16, and further, the optimum opening angle θ _opt is centered by the equation 3 or the equation 5. _{By setting the opening angle θ M2} of the inner magnet 16 within the permissible range, the difference between the permeance coefficients of the two permanent magnets 15 and 16 can be kept below a predetermined upper limit, and the irreversible demagnetization of the rotor 10 as a whole can be reduced. It becomes possible to suppress it. For example, when the total thickness of the two permanent magnets 15 and 16 is fixed, the distribution ratio of the _{thicknesses L m1} and L _{m2 that can keep the difference between the two permeance coefficients below a predetermined upper limit, and the inner magnet.} The combination with the opening angle θ _{M2 of} 16 can be set. Furthermore, in Formula _2, the zero-order term of _L m1 _/ L _m2, contribution of an average value Pc _a permeance coefficient of the two permanent magnets 15 and 16 are included. The values of the permeance coefficients of the two permanent magnets 15 and 16 vary depending on factors such as the amount of magnetic flux of the permanent magnets 15 and 16 and the magnitude of the inverse magnetic field, but the average value of the permeance coefficients of the two permanent magnets 15 and 16 the Pc _a, by substituting the equation 2, in consideration of those factors, it is possible to determine the relationship between the thickness ratio _L m1 _{/ L m2} opening angle theta _M2 and the permanent magnets 15, 16. For example, by changing the total thickness of the permanent magnets 15 and 16 used and the material, the amount of magnetic flux of the permanent magnets 15 and 16 can be changed, and the amount of current flowing through the coil of the stator 30 can be changed. , The magnitude of the reverse magnetic field changes, and these effects can be incorporated into Equation 2 in the form of a change in the magnitude of the permeance coefficient.

As described above, the opening angle theta _M2 of the inner magnet 16, the value of the difference in permeance coefficients of the two permanent magnets 15 and 16 is changed, and its opening angle theta _M2, the thickness ratio of the permanent magnets 15, 16 L _{Based on the relationship with m1} / L _m2 , it is possible to determine the _{opening angle θ M2 in} which the difference in permeance coefficient is equal to or less than a predetermined upper limit. On the other hand, the opening angle θ _M1 of the outer magnet 15 does not have a great influence on the value of the difference in the permeance coefficient, and the _{optimum opening angle θ opt} determined as the optimum value of _{the opening angle θ M2 of the inner magnet 16 by the above equation 2.} Does not depend on the opening angle θ _{M1 of the outer magnet 15.} Therefore, the opening angle θ _M1 of the outer magnet 15 is not particularly limited, and the outer magnet 15 having _{a predetermined thickness L m1} on the outer peripheral side of the rotor core 11 with _{respect to the inner magnet 16 having the opening angle θ M2 defined. The opening angle θ M1} may be arbitrarily set within the range in which the above can be accommodated. However, the opening angle θ _M1 of the outer magnet 15 is preferably 50 ° or more, more preferably 75 ° or more. Then, in the motor 1, the harmonic component of the magnetic flux density distribution formed in the air gap 50 is reduced, and the vibration and noise caused by the harmonics can be reduced. On the other hand, the opening angle θ _M1 of the outer magnet 15 is preferably 120 ° or less, more preferably 105 ° or less. Then, it is easy to secure a sufficient distance between the outer magnet 15 and the inner magnet 16, and the effect of improving the reluctance torque by arranging the permanent magnets 15 and 16 in a plurality of layers can be enhanced.

Hereinafter, the present invention will be described in detail with reference to Examples. Here, for the form in which the permanent magnets are arranged in two layers, the permeance coefficient when the thickness and opening angle of each permanent magnet are changed is estimated by simulation, and then the difference between the permeance coefficients of the two permanent magnets is calculated. The configuration that can be made smaller is considered.

[analysis method]
As shown in FIGS. 1 and 2, a model was created in which two layers of arc-shaped permanent magnets were concentrically arranged on the rotor. At this time, a model was created in which the thickness of the two layers of permanent magnets and the opening angle of each were variously changed. Then, a simulation was performed for each model, and the permeance coefficient of each permanent magnet was evaluated. The simulation was performed by electromagnetic field analysis using the finite element method (FEM).

In the simulation, the total thickness of the two permanent magnets was based on 3.0 mm. In addition to the thickness and opening angle of the two permanent magnets, the parameters used in the simulation are summarized in Table 1 below. In the simulation, the magnitude of the reverse magnetic field was changed in three ways of 80%, 100%, and 120% based on the case of 100% reverse magnetic field shown in Table 1 by changing the winding current.

[Analysis result]
(1) Relationship between the thickness and opening angle of permanent magnets and the permeance coefficient First, the total thickness of the two layers of permanent magnets is fixed, the distribution ratio of the thickness is variously changed, and the two permanent magnets are used. It was confirmed how the permeance coefficient of each permanent magnet changes by changing the opening angles θ _M1 and θ _M2. Here, the thickness L _m1 of the outer magnet is changed in the range of 0.7 mm to 1.5 mm at 0.1 mm intervals, and the total thickness of the two layers of permanent magnets is always 3.0 mm. , The thickness L _m2 of the inner magnet was also changed. Then, for each set of thickness, the opening angle θ _M1 of the outer magnet is changed in four ways in the range of 50 ° to 110 °, and the opening angle θ _M2 of the inner magnet is also changed from 90 ° to 165 °. In the range of °, it was changed at intervals of about 5 °. The magnitude of the reverse magnetic field was set to 100%.

As an example of the simulation results, FIG. 3 shows the distribution of the obtained permeance coefficients in the cases of _{L m1} = 0.9 mm, L _m2 = 2.1 mm, and θ _{M1 = 59.5 °.} (A) shows _{the case of θ M2} = 99.5 °, and (b) shows the case of _{θ M2 = 135.4 °.} As a big difference between FIGS. 3 (a) and 3 (b), in FIG. 3 (a), the permeance coefficient of the outer magnet is a large value of 1.0 or more in the entire area, whereas the inner magnet is The permeance coefficient of is 0.6 or less, and there is a large difference in the permeance coefficient between the outer magnet and the inner magnet. On the other hand, in FIG. 3B, the permeance coefficient of both the outer magnet and the inner magnet is generally in the range of 0.7 to 0.9, and the permeance coefficient is large between the two permanent magnets. There is no difference. Further, in both of FIGS. 3A and 3B, the permeance coefficient has a distribution inside each of the outer magnet and the inner magnet, and a remarkable distribution of the permeance coefficient is particularly provided inside the inner magnet. However, the degree of distribution of the permeance coefficient inside each permanent magnet is smaller in the case of FIG. 3 (b) than in the case of FIG. 3 (a). From this, in the case of FIG. 3 (b), the difference in the permeance coefficient is larger in both the inside of each permanent magnet and between the two layers of permanent magnets than in the case of FIG. 3 (a). You can see that it is getting smaller. Hereinafter, the difference in the permeance coefficients of the two layers of permanent magnets will be discussed based on the average value of the permeance coefficients in each of the outer and inner magnets.

FIGS. 4 to 6 show the permeance coefficients of the outer magnet (PM1) and the inner magnet (PM2) obtained when _{the opening angles θ M1} and θ _M2 are changed for a typical set of permanent magnet thicknesses. show. The thickness L _m1 of the outer magnet and the thickness L _m2 of the inner magnet are shown in FIG. 4, L _m1 = 0.9 mm, L _m2 = 2.1 mm, and in FIG. 5, L _m1 = 1.2 mm, L _m2 = 1.8 mm. , In FIG. 6, L _m1 = 1.5 mm and L _m2 = 1.5 mm. _{In the graph of θ M1} = 59.5 ° in FIG. 4, the leftmost data point and the second data point from the right correspond to the distribution maps of FIGS. 3 (a) and 3 (b), respectively. be.

In each of the graphs of FIGS. 4 to 6, the outer magnet (PM1) _{generally has a larger opening angle θ M2 as the} inner magnet has a larger _{opening angle θ M1.} There is a tendency that the permeance coefficient decreases and the permeance coefficient of the inner magnet (PM2) increases. In the form in which _{L m1} = L _{m2 in} FIG. 6, the line of the permeance coefficient of the outer magnet and the line of the permeance coefficient of the inner magnet are shown in all four graphs having different _{opening angles θ M1 of the outer magnet.} , Not intersecting. _{That is, even if the opening angle θ M2} of the inner magnet is changed within the range shown in the figure, the permeance coefficients of the two layers of permanent magnets cannot be made uniform. On the other hand, when L _m1 <L _m2 in FIGS. 4 and 5, in all four graphs with different opening angles θ _M1 of the outer magnet, the line of the permeance coefficient of the outer magnet and the permeance coefficient of the inner magnet The polygonal lines intersect with the opening angle θ _M2 of the inner magnet within the range of 90 ° to 165 °. That is, by appropriately selecting the opening angle θ _M2 of the inner magnet, the permeance coefficients of the two layers of permanent magnets can be made uniform. This tendency was obtained in all the thickness sets where _{L m1} <L _m2 , including those not shown. The intersection of FIG. 4 corresponds to the condition of FIG. 3 (b), and at the intersection, the distribution of the permeance coefficient between the outer magnet and the inner magnet and inside each permanent magnet is small. Is confirmed.

From this, it can be seen that by making the thickness of the inner magnet thicker than that of the outer magnet, the permeance coefficients of the two layers of permanent magnets can be set to be equal to or close to each other. By reducing the difference in the permeance coefficient of the two-layer permanent magnets, it is possible to make both of the two-layer permanent magnets in a well-balanced state in which irreversible demagnetization is unlikely to occur, and to increase the resistance of the rotor as a whole to irreversible demagnetization. can.

In each graph of FIGS. 4 and 5, and the permeance coefficient of the outer magnet polygonal line, the value of the opening angle theta _M2 at the intersection of fold lines of permeance coefficient of the inner magnet opening angle when the permeance coefficient of the two permanent magnets are aligned theta It becomes _M2 , that is, the optimum opening angle θ _opt. In each of FIGS. 4 and 5, when _{the value of the optimum opening angle θ opt} is read from the four graphs having different _{opening angles θ M1} of the outer magnet, the optimum opening is performed regardless of the opening angle θ _{M1 of the outer magnet.} It can be seen that the angle θ _opt is constant within an error range of about 10 °. _{That is, it can be seen that if the opening angle θ M2} of the inner magnet can be optimized without limiting the opening angle θ _M1 of the outer magnet to a specific value, the permeance coefficients of the two layers of permanent magnets can be made uniform. Similar results were obtained for other thickness sets (not shown).

_{The value of the opening angle θ M2} at the intersection of the permeance lines of the two permanent magnets, that is, the value of the optimum opening angle θ _opt is read, and the values are averaged for four different cases of the opening angle θ _{M1 of the outer magnet.} In No. 4, it is about 128 °, and in FIG. 5, it is about 148 °. From this, it can be said that the _{smaller the thickness L m2} of the inner magnet, the larger the optimum value θ _{opt of the opening angle θ M2 of the inner magnet.}

In FIG. 7, for _{all the thickness sets where L m1} <L _m2 , the optimum value θ _{opt of the opening angle θ M2} of the inner magnet is similarly set as a function of the thickness ratio L _m2 / L _m1 . (Reverse magnetic field 100%). According to FIG. 7, the optimum value θ _{opt of the opening angle θ M2} decreases monotonically with respect to the thickness ratio L _m2 / L _{m1 in the entire region.} That is, it is confirmed in the entire region that the optimum value θ _{opt of the opening angle θ M2 becomes larger when the thickness L m2} of the inner magnet is smaller, which is obtained by comparing FIGS. 4 and 5. FIG. 7 shows the results when the magnitude of the reverse magnetic field is changed, and the same monotonous decrease tendency is observed for all the reverse magnetic fields. The larger the reverse magnetic field, the smaller the optimum value of _{the opening angle θ M2.} It has become the one that was made to do.

As described above, in each of FIGS. 4 and 5, _{even if the value of the opening angle θ M1 of the outer magnet is changed, the opening angle θ M2} of the inner magnet at the intersection where the permeance coefficient break lines of the two permanent magnets intersect. The value of, that is, the value of the optimum opening angle θ _opt is constant with an error of about 10 °, but the value of the permeance coefficient at the intersection is also almost constant. Moreover, the value of the permeance coefficient at the intersection is about 0.76 in both FIGS. 4 and 5, and even if the thickness ratio of the permanent magnet is changed, the optimum value θ of _{the opening angle θ M2 of the inner magnet is θ.} It can be said that the permeance coefficient corresponding to _{opt does not change.}

In FIG. 8, for all the thickness sets, the permeance coefficient corresponding to the optimum value θ _{opt of the opening angle θ M2} of the inner magnet, that is, the value obtained by averaging the permeance coefficient at the above intersection with four opening angles θ _{M1. Is} displayed as a function of the thickness ratio L _m2 / L m1 (reverse magnetic field 100%). According to this, even if the thickness ratio L _m2 / L _m1 was changed, the value of the permeance coefficient was almost unchanged, and the optimum value of the _{opening angle θ M2 obtained by comparing FIGS. 4 and 5 was obtained.} It is confirmed that the permeance coefficient corresponding to θ _opt tends to be invariant regardless _{of the thickness ratio L m2} / L _{m1 of the permanent magnets in the entire region.} The average value of the displayed permeance coefficients in the entire region is 0.76 (100% demagnetizing field). FIG. 8 shows the results when the magnitude of the reverse magnetic field is changed. Similarly, in any of the reverse magnetic fields, the permeance coefficient is determined by _{the thickness ratio L m2} / L _{m1 of the permanent magnets.} The result is that there is almost no change. The value of the permeance coefficient becomes smaller as the inverse magnetic field becomes larger.

From the above results, the relationship between the thicknesses of the two permanent magnets is L _m1 <L _m2, and the opening angle θ _M2 of the inner magnet is set to the optimum opening angle θ _opt according to the thickness ratio L _m2 / L _m1. It can be seen that the permeance coefficients of the two permanent magnets can be aligned by setting to. Optimal opening angle theta _opt is greater the smaller the thickness _{L m @ 2,} a tendency of a monotonous decrease with respect to thickness ratio _L m2 _{/ L m1.} On the other hand, the permeance coefficient corresponding to _{the optimum opening angle θ opt} hardly changes even if the _{thickness ratio L m2} / L _{m1 is changed.}

(2) Formulation of the optimum value of the opening angle of the inner magnet Next, the optimum value θ _{opt of the opening angle θ M2} of the inner magnet is formulated as a function with respect to the ratio of the thicknesses of the two permanent magnets. In FIG. 7, in the _{region where the thickness ratio L m2} / L _m1 is small, the optimum value θ _opt of the opening angle θ _M2 tends to diverge. Therefore, the thickness ratio on the horizontal axis is set so as to be easy to formulate. , The reciprocal of L _m1 / L _m2 is shown in FIG.

In FIG. 9, the polygonal line shows a behavior in which the inclination becomes gentle once in the middle region. A cubic function can be mentioned as a function exhibiting such behavior. Therefore, the approximate curve in FIG. 9 is obtained by approximating the polygonal line of 100% of the inverse magnetic field with a cubic function (y = ax ³ + bx ^{2 + cx + d).} Even when the inverse magnetic field is 80% and 120%, the data points can be well approximated by using the same approximation formula only by changing the zero-order term d of the cubic function (not shown). Therefore, when a common cubic approximation formula that can approximate each of the three polygonal lines in FIG. 9 is obtained by using the zero-order term d as a function of the inverse magnetic field, the following equation 6 is obtained. The unit is the electrical angle (°).
θ _opt = 260 (L _m1 / L _m2 ) ³ 380 (L _m1 / L _m2 ) ² + 260 (L _m1 / L _m2 ) -4.38 · H + 86.0 (6)
Here, H represents the magnitude of the reverse magnetic field in units of kOe. The magnitude of the reverse magnetic field was set to the value calculated by the following equation 7 when the magnitude of the reverse magnetic field was 100%.
(3/2) ^0.5 · I · N / (L _m1 + L _m2 ) = 4.57 kOe (7)
Here, I is the current amplitude of the phase winding, which is 25.45A. N is the number of turns of the coil, which is 35T.

From the above, when the thicknesses L _m1 and L _m2 of the two permanent magnets are set to a predetermined ratio, the optimum value θ _{opt of the opening angle θ M2} that equalizes the permeance coefficients of the two permanent magnets is set by the above equation 6. can do. Equation 6 can be applied even if the magnitude of the reverse magnetic field changes.

The above equation 6 takes in the magnitude of the reverse magnetic field from the stator coil. The change in the magnitude of the reverse magnetic field appears as a change in the permeance coefficient in each permanent magnet, and the larger the reverse magnetic field, the more. The value of the permeance coefficient of each permanent magnet becomes smaller. Therefore, in Equation 6, we try to rewrite the equation by converting the contribution of the inverse magnetic field (H) to the zero-order term of _{L m1} / L _{m2 into the contribution of the permeance coefficient.} At this time, the data of FIG. 8 described above is used. FIG. 8 shows the permeance coefficient (permeance coefficient at the intersection of FIGS. 4 and 5) corresponding to the optimum value of the opening angle θ _{M2 with} respect to the thickness ratio L _m2 / L _{m1 of the permanent magnet.} Even if the thickness ratio L _m2 / L _{m1 of the} permanent magnet changed, the value of the permeance coefficient did not change, and the average value of the permeance coefficient was taken for each of the three cases with different magnitudes of the inverse magnetic field. The thing is shown on the horizontal axis of FIG. The vertical axis of FIG. 10 shows the magnitude of -4.38 · H + 86.0, which is the zero-order term of Equation 6, that is, the value of the vertical intercept in the approximate curve that approximates the data of FIG. 9 (unit: °). Is shown.

According to FIG. 10, the plot points of the three cases with different magnitudes of the reverse magnetic field are often on a straight line. This indicates that _{the zero-order term of L m1} / L _m2 in Equation 6 can be rewritten from the function of the inverse magnetic field (H) to the function of the permeance coefficient. Using the equation of the approximate straight line in FIG. 10 (intercept = 14.5 · PC _a +54.3), the equation 6 is rewritten with the zero-order term of _{L m1} / L _{m2 as the linear function of the permeance coefficient.} Equation 2 also described above is obtained.
^{_{θ opt = 260 (L m1 /}} L m2) 3 -380 (L m1 / L m2) 2 +260 (L m1 / L m2) + 14.5Pc a +54.3 (2)
Here, Pc _a is the average value of the permeance coefficient of the permanent magnets of the outer magnets and inner magnets, in the case where the permeance coefficient of the two permanent magnets are equal corresponds to the Bahamian scan coefficients.

Thus, in Equation 2, by expressing _{the zero-order term of L m1} / L _m2 as a function of the permeance coefficient, the permeance coefficient of the two permanent magnets is expressed in addition to the magnitude of the inverse magnetic field from the stator coil. If there are factors that change, the effects of those factors are taken in the form of changes in the permeance coefficient, and the optimum value θ _{opt of the opening angle θ M2} of the inner magnet is set to the thickness ratio L _m1 / L _{m2 of the permanent magnet.} Can be obtained as a function of. In addition to the reverse magnetic field from the stator coil, a change in the total thickness of the two layers of permanent magnets can be mentioned as a factor that changes the permeance coefficient of the permanent magnets. Increasing the total thickness of the permanent magnets increases the permeance coefficient of each permanent magnet.

In FIGS. 11 (a) and 11 (b), the inner magnet is opened when the total thickness of the two layers of permanent magnets is 2.0 mm, which corresponds to 1 / 1.5 of the above 3.0 mm. The change in the permeance coefficient of the outer magnet (PM1) and the inner magnet (PM2) when the angle θ _{M2 is changed is shown.} (A) shows the case where L _m1 = 0.6 mm and L _m2 = 1.4 mm, and (b) shows the case where L _m1 = 0.8 mm and L _m2 = 1.2 mm. In (a), the magnitude of the reverse magnetic field from the stator coil is a value corresponding to the magnetic field reduction of "80%" in the simulation in which the thickness of the permanent magnet is 3.0 mm. ) Is a value corresponding to the demagnetizing field of "120%".

_{From FIG. 11A, the value of the opening angle θ M2} at the intersection of the two polygonal lines, that is, the optimum opening angle θ _opt can be read as 137 °. The value of the permeance coefficient at the intersection is 1.06. On the other hand, based on Equation 2, i.e. the value of the thickness _{L m1, L m @ 2,} the values of the 1.06 as permeance coefficient Pc _a into equation 2 and calculates the optimum opening angle theta _opt, 132 It becomes °. This value matches the above reading with an accuracy of 5 °. On the other hand, from FIG. 11B, _{the value of the opening angle θ M2} at the intersection of the two polygonal lines, that is, the optimum opening angle θ _opt can be read as 145 °. The value of the permeance coefficient at the intersection is 0.545. On the other hand, when the optimum opening angle θ _opt is calculated based on Equation 2, it becomes 144 °. This value matches the above reading with an accuracy of 1 °.

Further, in FIG. 11C, when the total thickness of the two layers of permanent magnets is 4.5 mm, which corresponds to 1.5 times the above 3.0 mm, the opening angle θ _M2 of the inner magnet is set. The change in the permeance coefficient of the outer magnet and the inner magnet when changed is shown. The case where L _m1 = 1.8 mm and L _m2 = 2.7 mm is shown. The magnitude of the reverse magnetic field from the stator coil is a value corresponding to the magnetic field reduction of "120%" in the simulation in which the thickness of the permanent magnet is 3.0 mm.

_{From FIG. 11C, the value of the opening angle θ M2} at the intersection of the two polygonal lines, that is, the optimum opening angle θ _opt can be read as 144 °. The value of the permeance coefficient at the intersection is 0.44. On the other hand, when the optimum opening angle θ _opt is calculated based on Equation 2, it is 142 °. This value matches the above reading with an accuracy of 2 °.

As described above, regardless of whether the total thickness of the two layers of permanent magnets is smaller or larger than the above 3.0 mm, the opening angle θ _M2 of the inner magnet is determined by the common equation 2. The optimum value θ _opt can be well expressed with an accuracy of about ± 5 °. That is, in the above equation 2, _{the zero-order term of L m1} / L _m2 is determined based on the data obtained by changing the magnitude of the reverse magnetic field from the stator coil. Not limited to this, factors that change the permeance coefficient of the permanent magnet, such as the absolute value of the thickness of the permanent magnet, can be incorporated into the zero-order term of Equation 2 to determine the optimum value θ _{opt of the opening angle θ M2.} ..

(3) Tolerance range of the opening angle θ _M2 of the inner magnet In the above, the optimum value θ _{opt of the opening angle θ M2} of the inner magnet capable of aligning the permence coefficients of the two layers of permanent magnets is determined by using Equation 2 for the permanent magnet. It was clarified that it can be expressed as a function of the thickness ratio L _m1 / L _{m2 of.} The irreversible demagnetization in the rotor can be suppressed most when the permeance coefficients of the two layers of permanent magnets are the same, but the permeance coefficients of the two layers of permanent magnets are not always completely the same. However, it is possible to obtain a sufficiently high resistance to irreversible demagnetization. Therefore, it is considered that an allowable range is provided around the optimum value θ _opt at the opening angle θ _{M2 of the inner magnet.}

Here, it is assumed that the upper limit of the allowable difference between the values of the permeance coefficients of the two layers of permanent magnets is B. In this case, _{the opening angle θ M2} of the inner magnet is set within a range of about ± B / 2 with respect to the permeance coefficient corresponding to _{the optimum value θ opt, that is, the permeance coefficient at the intersection of the graphs in FIGS.} You just have to do it. Therefore, it is considered that the range corresponding to the range of ± 2 / B as the permeance coefficient is assigned to _{the value of the opening angle θ M2 of the inner magnet.} That is, when the proportional relationship of _{θ M2} = C · Pc ₂ is established between the opening angle θ _M2 and the permeance coefficient Pc ₂ of the _{inner magnet, the allowable range of the opening angle θ M2} is as shown in Equation 3. Can be expressed in.
θ _opt −C ・ B / 2 ≦ θ _M2 ≦ θ _opt + C ・ B / 2 (3)

_{In order to obtain the proportionality constant C between the permeation coefficient Pc 2} in the inner magnet and the opening angle θ _M2 , in FIG. 12, the thickness ratio L _m1 / L _m2 of the permanent magnet is taken as the horizontal axis, and the permence coefficient Pc _{2 of the inner magnet is taken.} The slope of the opening angle θ _M2 with respect to the _{relative angle (Δθ M2} / ΔPc ₂ ) is shown on the vertical axis. Each plot point is inclined by approximating the entire area to a straight line with respect to the polygonal line _{of the permeance coefficient Pc 2} of the inner magnet (PM2) when the _{opening angle θ M2 is changed, as shown in FIGS.} Corresponds to the calculated one. FIG. 12A shows _{a case where θ M1} = about 60 °, and FIG. 12B _{shows a case where θ M1} = about 75 °. Here, regarding the opening angle θ _M1 of the outer magnet, “about” is displayed in the region of approximately ± 5 °, and the simulation was performed by changing _{the thickness ratio L m1} / L _{m2 of the permanent magnet.} At this time, it is taken into consideration that the _{opening angles θ M1 are not completely aligned.} 12 (a) and 12 (b) show the results for each of the three reverse magnetic fields.

According to FIG. 12, in both cases (a) and (b), the value on the vertical axis is 100 over the entire area of the _{permanent magnet thickness ratio L m1} / L _{m2 and in any of the three reverse magnetic fields.} It is above °. That is, it can be seen that the value of the coefficient C to be substituted in the above equation 3 is C ≧ 100 °. Here, the coefficient C is _{for adding an acceptable range to the opening angle θ M2} of the inner magnet, and if it is set to a small value, the opening angle θ _M2 is widened to an unacceptable range. You can avoid the situation. Therefore, in Equation 3, C = 100 ° may be set.

Assuming that the permeance coefficient B provided in the permeance coefficient is 0.1 in the formula 3, the formula 3 becomes as shown in the formula 4 below.
θ _opt -5 ° ≤ θ _M2 ≤ θ _opt + 5 ° (4)
That is, as the opening angle θ _M2 of the inner magnet, a value in the range of ± 5 ° centered on the optimum value θ _{opt is allowed.} The polygonal lines in FIGS. 4 and 5 show the opening angle θ _M2 of the inner magnet changed by about 5 °. In the graph, some rattling is observed in the polygonal line, and the opening angle θ _M2 It can be interpreted that it is appropriate to set the permissible range in. Therefore, if the opening angle θ _{M2 of the inner magnet is set within a range of ± 5 ° around the optimum opening angle θ opt} as in Equation 4, the rotor having two layers of permanent magnets is resistant to irreversible demagnetization. Can be said to be sufficiently enhanced.

Further, consider displaying the permissible range for the absolute value of the permeance coefficient with B = 0.1 as a ratio A to the magnitude of the permeance coefficient. As shown in FIG. 8, when the magnitude of the inverse magnetic field is 100%, the value of the permeance coefficient corresponding to the optimum value θ _{opt of the opening angle θ M2 is 0.76.} When the error of B = 0.1 is converted into the ratio to this permeance coefficient, it becomes 13%. _{Therefore, if the tolerance A as a} ratio of the permeance coefficient of the two-layer permanent magnets to the average value Pca is set to about 15%, the rotor having the two-layer permanent magnets has sufficient resistance to irreversible demagnetization. It can be said that it can be enhanced.

The embodiment of the present invention has been described above. The present invention is not particularly limited to these embodiments, and various modifications can be made.

1 Motor (rotary electric machine)
10 Rotor (permanent magnet rotor)
11 Rotor core 15 Outer magnet 16 Inner magnet 30 Stator (stator)
L _m1 Thickness of outer magnet L _m2 Thickness of inner magnet M Permanent magnet R Center of rotation of rotor core S Slot θ _M1 Opening angle of outer magnet θ _M2 Opening angle of inner magnet

Claims (7)

A permanent magnet rotor having a rotor core and a plurality of permanent magnets embedded in the rotor core and forming magnetic poles.
In the cross section orthogonal to the rotation axis of the rotor core,
Each of the plurality of permanent magnets has a convex arc shape toward the inner peripheral side of the rotor core, and is arranged in a layered manner of two or more layers from the outer peripheral side to the inner peripheral side of the rotor core.
The thickness of the permanent magnet is larger than that of the permanent magnet arranged on the inner peripheral side of the rotor core.
A permanent magnet rotor in which the difference between the permeance coefficients of any two permanent magnets adjacent to each other in the radial direction of the rotor core is 15% or less of the average value of the permeance coefficients of the two permanent magnets. The permanent magnet rotor according to claim 1, wherein the plurality of permanent magnets are arranged in two layers of an outer magnet and an inner magnet from the outer peripheral side to the inner peripheral side of the rotor core. The plurality of permanent magnets are arranged in two layers, an outer magnet and an inner magnet, from the outer peripheral side to the inner peripheral side of the rotor core.
The permanent magnet rotor according to claim 1 or 2, wherein the opening angle of the inner magnet is θ _{M2 in} terms of electrical angle, and θ _opt −5 ° ≦ θ _M2 ≦ θ _{opt + 5 °.}
Here, the outer magnet and the thickness of the inner magnet, and each L _m1 and L _{m @ 2,} the average value of the permeance coefficient of the inner magnet and the outer magnet as Pc _a, the theta _opt, the unit of ° As,
^{_{θ opt = 260 (L m1 /}} L m2) 3 -380 (L m1 / L m2) 2 +260 (L m1 / L m2) is ₊ 14.5Pc a _+54.3. The permanent magnet rotor according to claim 3, wherein the opening angle of the outer magnet is θ _{M1 in} terms of electrical angle, and 50 ° ≤ θ _{M1 ≤ 120 °.} The permanent magnet rotor according to any one of claims 1 to 4, wherein the plurality of permanent magnets have a concentric arcuate shape. The permanent magnet rotor according to any one of claims 1 to 5, wherein the plurality of permanent magnets are hot plastic working magnets. A rotating electric machine having the permanent magnet rotor according to any one of claims 1 to 6.

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