DE102023114887A1 - Rotating electric machine - Google Patents

Abstract

A rotating electrical machine (1) has a stator (21), teeth (21b), coils (22), a rotor (10), a rotor core (11) and permanent magnets (M), with a cross section perpendicular to the axis of rotation ( O) of the rotor (10), an inner peripheral surface of the teeth (21b) has an arcuate shape centered on the axis of rotation (O), each of the magnetic poles independently having a centrally thickened shape, in which an outer edge of the permanent magnet (M) is on the outside in the radial direction of the Rotor (10) has an arc shape centered on the axis of rotation, an inner edge of the permanent magnet (M) on the inside in the radial direction of the rotor has a shape which faces the inside in the radial direction of the rotor (10) as an arc shape centered on the axis of rotation (O). protrudes, and a thickness between the outer edge of the permanent magnet (M) and the inner edge of the permanent magnet (M) is greatest at a location of the center of the magnetic pole, and each of the permanent magnets (M) of the rotor (10) has a concentrated orientation, in which a magnetization direction is inclined in a direction towards the center of the magnetic pole, namely on the outside in the radial direction of the rotor (10) outwards along a circumferential direction of the rotor (10).

Description

Technical area

The present invention relates to a rotating electric machine, and more particularly to a rotating electric machine having a rotor with a permanent magnet on a surface of a rotor core.

State of the art

• Druckschrift 1: WO 2019/069539 A1
• Druckschrift 2: JP 2020-191692 A

As a type of rotating electric machine with a rotor and a stator, there is a surface permanent magnet (SPM) motor with a rotor in which a permanent magnet is attached to the surface of a rotor core (ie, permanent magnet (synchronous) motor with surface magnets) . For an SPM motor, studies have been made on the shape, arrangement, magnetization direction and the like to obtain desired characteristics. For example, in Document 1, the arrangement and shape of a magnetic part (permanent magnet) and a magnetic part (ferromagnetic body) in an SPM motor are discussed from the viewpoint of reducing a cogging torque and reducing a torque ripple while avoiding the Torque reduction examined. Document 2 discloses that, from the viewpoint of reducing torque, a current supplied to the motor is a trapezoidal wave, and each magnetic pole is oriented (concentrated orientation) so that a direction of easy magnetization is concentrated toward the stator side.

• Document 1: WO 2019/069539 A1
• Document 2: JP 2020-191692 A

Brief description of the invention

As exemplified in Documents 1 and 2, it is possible to improve important characteristics such as reducing cogging torque and improving output torque by designing the shape, arrangement, magnetization direction, and the like of a permanent magnet in an SPM motor. However, it is difficult to implement both cogging torque reduction and permanent magnet demagnetization prevention while maintaining a high output torque. For example, from the inventors' studies, it is clear that in the case where a permanent magnet having a plano-convex shape (circle segment shape) similar to that used in Document 1 is used, it will vary depending on the details of the shape and magnetization direction of the permanent magnet (see “Model 1 " in 6A and 6B , and “plano-convex” in 9A and 9B) There is a case where it is impossible to sufficiently implement torque retention and cogging torque improvement. In the case where concentrated alignment is applied to an arc-shaped permanent magnet as disclosed in Reference 2, it is difficult to reduce the cogging torque and avoid demagnetization of the permanent magnet (see “Arc” in 9A , 9B and 10A) . It is important to implement both the reduction of the cogging torque and the prevention of demagnetization of the permanent magnet while maintaining a high output torque, from the perspective of implementing the maintenance of the required torque and the reduction of vibration and noise while maintaining a usage amount of the permanent magnet is reduced.

It is an object of the present invention to provide a rotating electrical machine in which a permanent magnet is provided on the surface of a rotor core, the rotating electrical machine being able to both reduce a cogging torque and prevent demagnetization of the permanent magnet, wherein a high torque is maintained.

• [1] Eine rotierende elektrische Maschine gemäß der vorliegenden Erfindung weist auf: einen Stator, der einen Statorkern aufweist, der hohlzylindrische Form und mehrere Zähne und einen hohlen Bereich aufweist; und um die jeweiligen Zähnen gewundene Spulen; und einen Rotor, der in dem hohlen Bereich des Statorkerns angeordnet ist und einen Rotorkern mit einer Außenumfangsfläche aufweist; und mehrere an der Außenumfangsfläche des Rotorkerns befestigte und jeweils einen Magnetpol darstellende Permanentmagnete, wobei jeder der Zähne des Statorkerns eine Innenumfangsfläche aufweist, die Innenumfangsfläche der Zähne des Statorkerns in einem Querschnitt senkrecht zur Rotationsachse des Rotors eine zur Rotationsachse zentrierte Bogenform aufweist, und jeder der Permanentmagnete des Rotors, für jeden der Magnetpole unabhängig, eine mittenverdickte Form aufweist, bei der eine Außenkante des Permanentmagneten an der Außenseite in radialer Richtung des Rotors eine zur Rotationsachse zentrierte Bogenform aufweist, eine Innenkante des Permanentmagneten an der Innenseite in radialer Richtung des Rotors eine Form aufweist, die zur Innenseite in radialer Richtung des Rotors mehr als eine zur Rotationsachse zentrierte Bogenform vorspringt, und eine Dicke zwischen der Außenkante des Permanentmagneten und der Innenkante des Permanentmagneten an einer Stelle der Mitte des Magnetpols am größten ist, und jeder der Permanentmagnete des Rotors eine konzentrierte Ausrichtung aufweist, bei der eine Magnetisierungsrichtung in einer Richtung zur Mitte des Magnetpols an der Außenseite in radialer Richtung des Rotors geneigt ist, und zwar nach auswärts entlang einer Umfangsrichtung des Rotors zunehmend.
• [2] Hierbei kann beim Aspekt [1] die Innenkante des Permanentmagneten im Querschnitt senkrecht zur Rotationsachse des Rotors linear sein.
• [3] Alternativ kann beim Aspekt [1] die Innenkante des Permanentmagneten zur Innenseite in radialer Richtung des Rotors ausbeulen.
• [4] Bei jedem der Aspekte [1] bis [3] kann die rotierende elektrische Maschine ferner eine Schutzröhre am Außenumfang des Rotors aufweisen, wobei die Schutzröhre eine zylindrische Form aufweist und aus einem nicht-magnetischen Material gebildet ist, wobei die Außenkante des Permanentmagneten sich entlang der Innenumfangsfläche der Schutzröhre erstreckt.
• [5] Bei jedem der Aspekte [1] bis [4] kann ein Öffnungswinkel der Außenkante des Permanentmagneten in Bezug auf die Rotationsachse innerhalb eines Bereichs von ± 10% in Bezug auf den Öffnungswinkel der Innenumfangsfläche der Zähne in Bezug auf die Rotationsachse liegen.
• [6] Bei jedem der Aspekte [1] bis [5] kann in dem Rotor der Rotorkern einen konvexen Bereich zwischen den einander benachbarten Magnetpolen aufweisen, wobei der konvexe Bereich in Kontakt mit den Permanentmagneten an beiden Seiten steht und zur Außenseite in der radialen Richtung des Rotors vorspringt, als die Innenkante des Permanentmagneten.

In order to achieve the above object, the rotary electric machine of the present invention has the following configuration:

• [1] A rotating electric machine according to the present invention includes: a stator having a stator core having a hollow cylindrical shape and a plurality of teeth and a hollow portion; and coils wound around the respective teeth; and a rotor disposed in the hollow portion of the stator core and having a rotor core having an outer peripheral surface; and a plurality of permanent magnets attached to the outer peripheral surface of the rotor core and each constituting a magnetic pole, each of the teeth of the stator core having an inner peripheral surface which Inner circumferential surface of the teeth of the stator core in a cross section perpendicular to the axis of rotation of the rotor has an arcuate shape centered on the axis of rotation, and each of the permanent magnets of the rotor, for each of the magnetic poles independently, has a centrally thickened shape in which an outer edge of the permanent magnet is on the outside in the radial direction of the rotor has an arc shape centered on the axis of rotation, an inner edge of the permanent magnet on the inside in the radial direction of the rotor has a shape that projects to the inside in the radial direction of the rotor more than an arc shape centered on the axis of rotation, and a thickness between the outer edge of the permanent magnet and the inner edge of the permanent magnet is largest at a location of the center of the magnetic pole, and each of the permanent magnets of the rotor has a concentrated orientation in which a magnetization direction is inclined in a direction toward the center of the magnetic pole on the outside in the radial direction of the rotor, and although increasing outwards along a circumferential direction of the rotor.
• [2] In aspect [1], the inner edge of the permanent magnet can be linear in cross section perpendicular to the axis of rotation of the rotor.
• [3] Alternatively, in aspect [1], the inner edge of the permanent magnet can bulge towards the inside in the radial direction of the rotor.
• [4] In each of aspects [1] to [3], the rotating electric machine may further include a protective tube on the outer periphery of the rotor, the protective tube having a cylindrical shape and being formed of a non-magnetic material, the outer edge of which is a permanent magnet extends along the inner peripheral surface of the protective tube.
• [5] In each of aspects [1] to [4], an opening angle of the outer edge of the permanent magnet with respect to the rotation axis may be within a range of ±10% with respect to the opening angle of the inner peripheral surface of the teeth with respect to the rotation axis.
• [6] In any of aspects [1] to [5], in the rotor, the rotor core may have a convex portion between the adjacent magnetic poles, the convex portion being in contact with the permanent magnets on both sides and to the outside in the radial direction of the rotor protrudes than the inner edge of the permanent magnet.

In the rotating electric machine according to the invention of the above [1], the permanent magnet, in cross section perpendicular to the rotation axis of the rotor, has a predetermined center-thickened shape, and the magnetization direction is a concentrated orientation. Due to the effect of the shape and magnetization direction of the permanent magnet, in the rotating electric machine, a high torque is obtained, an air gap magnetic flux density distribution with a wave shape close to a sine wave is formed, and a cogging torque is prevented (or reduced). In an outer area in the circumferential direction of the magnetic pole, a permeance coefficient of the permanent magnet increases and demagnetization is prevented.

In aspect [2], the inner edge of the permanent magnet is linear in cross section perpendicular to the axis of rotation of the rotor, and the permanent magnet has a plano-convex (circular section-shaped) cross section. Such a permanent magnet shows a strong effect in terms of torque improvement, cogging torque prevention and demagnetization prevention in a rotating electric machine. It can also be easily manufactured.

In aspect [3], the inner edge of the permanent magnet bulges toward the inside in the radial direction of the rotor, and the permanent magnet has a biconvex shape (lens or almond shape). Similar to the permanent magnet with a plano-convex shape, such a permanent magnet shows a strong effect in terms of torque improvement, cogging torque prevention and demagnetization prevention in a rotating electrical machine. In particular, a thickness of the central portion of the permanent magnet is increased, thereby exerting an excellent effect of preventing demagnetization.

In aspect [4], a protective tube is provided on the outer circumference of the rotor. In the case that the protective tube is formed in a cylindrical shape centered on the rotation axis of the rotor, and the outer edge of the permanent magnet is also formed with an arc shape centered on the rotation axis of the rotor, the outer edge of the permanent magnet extends along the inner peripheral surface the protective tube. The protective tube serves to prevent the permanent magnet from scattering due to centrifugal force. Shaping the permanent magnet in a shape in which the outer edge of the permanent magnet extends along the inner peripheral surface of the protective tube is easy Measure for obtaining a rotating electric machine capable of both preventing cogging torque and preventing demagnetization of the permanent magnet while maintaining high torque.

In aspect [5], an opening angle of the outer edge of the permanent magnet with respect to the rotation axis is within a range of ±10% with respect to the opening angle of the inner peripheral surface of the teeth with respect to the rotation axis. In this way, an opening angle of the permanent magnet is close to the opening angle of the teeth, thereby exerting an excellent cogging torque preventing effect.

In aspect [6], the convex region is provided on the rotor core at a location between the adjacent magnetic poles. The convex portion prevents the permanent magnet from being displaced and provides a magnetic flux path of the permanent magnet in a direction toward the teeth of the stator core to promote efficient utilization of the magnetic flux.

Brief description of the drawings

• 1 Fig. 10 is a cross-sectional view showing a configuration of a motor having a plano-convex shape permanent magnet with a uniform gap according to an embodiment of the present invention;
• 2 is a cross-sectional view of a part of the engine according to the embodiment of the present invention, and corresponds to an enlarged view of 1 ;
• 3 Fig. 10 is a cross-sectional view of a portion of the motor according to an aspect of the prior art, showing a permanent magnet having a plano-convex shape with a non-uniform gap;
• 4A shows a magnetic flux density distribution in a model 1 in which parallel alignment was applied to a permanent magnet having a plano-convex shape with a non-uniform gap;
• 4B shows a magnetic flux density distribution in a model 2 in which concentrated alignment was applied to a permanent magnet with a plano-convex shape with a uniform gap;
• 5A is a graph comparing magnetic flux density waveforms in an air gap with respect to Models 1 to 3;
• 5B is a diagram comparing amplitudes of a fundamental wave component of an air gap magnetic flux density with respect to Models 1 to 3;
• 6A is a graph comparing maximum torques with respect to models 1 to 3 in cases where the volumes of the permanent magnets were equal;
• 6B is a diagram comparing cogging torques with respect to models 1 to 3 in cases where the volumes of the permanent magnets were equal;
• 7A is a graph comparing maximum torques with respect to Models 1 to 3 in cases where the maximum torques were the same;
• 7B is a graph comparing cogging torques with respect to Models 1 to 3 in cases where the maximum torques were equal;
• 8A , 8B and 8C are cross-sectional views showing a configuration of three motors in which the permanent magnets have different shapes; 8A shows a permanent magnet with an arcuate shape, 8B shows a permanent magnet with a plano-convex shape with a uniform gap, and 8C shows a permanent magnet with a biconvex shape with a uniform gap;
• 9A is a graph comparing maximum torques in the cases of concentrated and parallel alignment in the cases where the three permanent magnets of 8A , 8B and 8C were used;
• 9B is a diagram comparing cogging torques in the cases of concentrated and parallel alignment in the cases where the three permanent magnets of 8A , 8B and 8C were used;
• 10A , 10B , 10C and 10D are diagrams showing the distribution of a permeance coefficient in four aspects differing in magnet shape and magnetization direction; 10A , 10B and 10C show aspects in which the concentrated alignment on the permanent magnets with the shape of 8th , 8B and 8C was applied, and 10D shows an aspect in which the parallel alignment on the permanent magnet with a plano-convex shape with an uneven gap as in 3 was applied;
• 11Aist a diagram showing a change in maximum torque in the case where a ratio of an opening angle (θ _M ) of a permanent magnet to an opening angle (θ _S ) of a stator was varied under an aspect in which the concentrated orientation on a permanent magnet with plano-convex shape with a uniform gap was applied, and three angles were adopted as the orientation angles of the concentrated orientation; and
• 11B is a diagram showing a change in cogging torque in the case where a ratio of an opening angle (θ _M ) of a permanent magnet to an opening angle (θ _S ) of a stator was varied under an aspect in which the concentrated orientation on a permanent magnet with plano-convex shape with a uniform gap was applied, and three angles were adopted as the orientation angles of the concentrated orientation.

Description of the embodiments

Below, a rotating electric machine according to an embodiment of the present invention will be described in more detail with reference to the drawings.

Rotating electric machine configuration

An overview of a motor 1 as a rotating electrical machine according to an embodiment of the present invention is shown in 1 shown in a cross-sectional view perpendicular to the axis of rotation O. 2 is an enlarged part of the view of 1 . The following mainly describes the case where the rotating electric machine is a motor, but the same configuration can also be applied to the case where the rotating electric machine is an electric generator.

The motor 1 is configured as a surface permanent magnet (SPM) motor. The motor 1 includes a stator 20 with a stator core 21 with a hollow cylindrical shape, and a rotor 10 which is held coaxially and axially rotatable in a hollow region of the stator core 21.

Below, unless otherwise stated, a structure (shape and arrangement) of each region and a magnetization direction in cross section perpendicular to the rotation axis O of the rotor 10 are shown as in 1 and 2 shown. Further, directions such as “radial direction,” “circumferential direction,” “outer circumference,” “inner circumference,” “outside” and “inside” refer to directions with respect to the rotor 10 unless otherwise specified. In addition, expressions representing the shape or arrangement of a component such as "arc", "straight line" and "vertical" imply not only a geometrically strict concept, but also a deviation within a tolerance range for an engine of this type.

The stator 20 includes a stator core 21 and coils 22. The stator core 21 is formed by laminating a plurality of electromagnet steel sheets, and integrally includes a yoke portion 21a having a substantially annular shape and a plurality of teeth 21b projecting from the yoke portion 21a toward the inside of the ring shape. The coils 22 are wound around the respective teeth 21b. An inner peripheral surface 21c of each of the teeth 21b has an arc shape centered on the rotation axis O of the rotor 10.

The rotor 10 includes a rotor core 11 having a substantially cylindrical outer shape, and a plurality of permanent magnets M attached to the outer peripheral surface of the rotor core 11. A protective tube 30 is provided on the outer circumference of the rotor 10. The protective tube 30 is configured as a (hollow) cylindrical member made of a non-magnetic material such as non-magnetic stainless steel. A hollow portion is formed in the center of the rotor core 11, and a shaft 40 is inserted through the hollow portion. In the state in which the rotor 10 is housed coaxially in the hollow region of the stator core 21, an air gap G is maintained between the stator 20 and the outer peripheral surface of the rotor core 11. The air gap G is filled with air.

In the rotor 10, the plurality of permanent magnets M represent respective magnetic poles, and the permanent magnets M are independently arranged as respective magnetic poles. That is, the several permanent Magnets M are arranged separately from one another in the circumferential direction of the rotor 10. The polarities of the permanent magnets M are alternately different for the magnetic poles. The number of poles (number of permanent magnets M) of the rotor 10 and the number of slots (number of teeth 21b) of the stator 20 are not particularly limited as long as they function as a motor. In the illustrated aspect, the number of poles is 10 and the number of slots is 12, and this combination can be suitably adopted for the motor 1 according to the present embodiment.

Overview of the rotor configuration

A structure of the rotor 10 will be described below. The rotor core 11 is formed by laminating a plurality of electromagnet steel sheets and has a substantially (hollow) cylindrical shape. The permanent magnets M are attached to the outer peripheral surface of the rotor core 11. The permanent magnets M are exposed on the outer circumference of the entire rotor 10. The permanent magnets M are suitably attached to the outer peripheral surface of the rotor core 11 with an adhesive, and the effects of the adhesive and the protective tube 30 prevent the permanent magnets M from being dispersed (thrown off) by the centrifugal force when the rotor 10 rotates.

Each of the plurality of permanent magnets M has a center thickened shape, which will be described later independently for each magnetic pole. In the illustrated aspect, each of the permanent magnets M has a plano-convex shape (circular segment shape) among the center-thickened shapes. Furthermore, each of the permanent magnets M has a concentrated orientation. In the concentrated alignment, as shown by the single-headed arrows in 2 indicated, the direction of magnetization in a direction towards the center C of the magnetic pole on the outside (stator side) is more inclined to the radial direction the further outwards you go in the circumferential direction. That is, in each region of the permanent magnet M along the circumferential direction, the magnetization direction converges in the radial direction toward the center C of the magnetic pole toward the outside. Preferably, the magnetization direction may converge to a single focal point in each region along the circumferential direction of each of the magnetic poles. In this case, an orientation angle θ _O is not particularly limited, but in a case such as the shown 10-pole rotor, a range of 40° to 80° may be suitable. The orientation angle θ _O is defined as the angle between a straight line connecting an end portion of the permanent magnet M on its inner peripheral side and the orientation focal point with a direction perpendicular to the center axis (straight line of the rotor 10 in the radial direction passing through the center C of the magnetic pole occurs) of the magnetic pole is formed.

The kind of the permanent magnet M is not particularly limited, but a metal magnet is preferred. That is, except for the surface, it is preferable that no intentionally added metal oxides or organic compounds are contained and only a metallic magnetic material is contained. Further, a hot-formed magnet having fine crystal grains of a magnet material is preferred. The hot-formed magnet can be formed into a center-thickened shape and can relatively easily obtain concentrated orientation by magnetization.

In the motor 1 of the present embodiment, the permanent magnet M has a center-thickened shape and the magnetization direction is a concentrated orientation, thereby making it possible to reduce a cogging torque and avoid demagnetization (self-demagnetization) of the permanent magnet while achieving a high torque keep. Details of the shape of the permanent magnet M and the effects of the shape and magnetization direction of the permanent magnet M on the characteristics of the motor 1 will be described below.

In the rotor 10, the rotor core 11 preferably has a convex region 11a at a location between adjacent magnetic poles. The convex portion 11a is provided integrally with the rotor core 11 as a portion which projects more toward the outside in the radial direction than each inner edge M2 of the permanent magnets M on both sides along the circumferential direction, and which is in contact with the permanent magnets M on both sides . In the illustrated aspect, the convex portions 11a are in contact with corresponding peripheral edges M3 of the permanent magnets M on both sides. The convex portions 11a serve to prevent the permanent magnets M from displacing in the circumferential direction and also to help improve the effective magnetic flux by the effect of the shape of the permanent magnets M, as will be described in more detail below.

Details of Shape of Permanent Magnets In the motor 1 of the present embodiment, each of the plurality of permanent magnets M in the rotor 10 has a predetermined center thickened shape. The That is, in the case of the permanent magnet M, an outer edge M1, which is the edge on the outside in the radial direction, has an arc shape centered on the rotation axis O of the rotor 10. On the other hand, the inner edge M2, which is the edge on the inner side in the radial direction of the rotor 10, has a shape that projects further inward in the radial direction than an arc shape centered on the rotation axis O of the rotor 10. A thickness between the outer edge M1 and the inner edge M2, that is, a distance between the outer edge M1 and the inner edge M2 along the center axis C of the magnetic pole, is largest in the center of the magnetic pole.

The outer edge M1 of the permanent magnet M has an arc shape centered on the rotation axis O of the rotor 10, whereby the outer edge M1 is in concentric relationship with the inner peripheral surface 21c of the teeth 21b of the stator core 21, which inner peripheral surface 21c is similarly centered on the rotation axis O of the rotor 10 Has an arch shape. Therefore, a distance (length along the center axis C) of the air gap G between the permanent magnet M and the stator core 21 is substantially the same over the entire area of the permanent magnet along the circumferential direction, as shown by the double arrow in 2 indicated. Therefore, the shape of the permanent magnet M of the present embodiment can be called a center-thickened shape with a uniform gap. Further, in the case that the protection tube 30 having a cylindrical shape is provided on the outer periphery of the rotor 10, the outer edge M1 of the permanent magnet M has a shape along the inner peripheral surface of the protection tube 30.

The inner edge M2 of the permanent magnet M does not have a shape concentric with the outer edge M1, as in the case of the permanent magnet with an arc shape as in 8A , but protrudes further inwards in the radial direction of the rotor 10, as such a concentric arc shape. The inner edge M2 may bulge inward in the radial direction, may be linear, or may be curved outward in the radial direction, as long as the inner edge M2 projects further inward in the radial direction as an arc shape concentric with the outer edge M1, and the greatest thickness of the permanent magnet M in the center C of the magnetic pole. However, the inner edge M2 preferably has a linear shape or a shape that bulges inward in the radial direction. The shape of the entire permanent magnet M including the inner edge M2 is preferably symmetrical with respect to the central axis C.

In the case that the inner edge M2 is linear (straight), the permanent magnet M has a plano-convex (circular section-shaped) shape, as in the 1 , 2 and 8B shown. On the other hand, in the case that the inner edge M2 has a shape that bulges inward in the radial direction, the permanent magnet M has a biconvex (lenticular or almond-shaped) shape as shown in FIG 8C shown. As will be described later, regardless of whether the permanent magnet M has a plano-convex or biconvex shape, a motor having excellent characteristics of high torque, reducing cogging torque and preventing demagnetization of the permanent magnet M is provided. However, the case of the biconvex shape has a greater effect in preventing demagnetization. On the other hand, the productivity is higher in the case of the plano-convex shape of the permanent magnet M. In the case that the permanent magnet M has a biconvex shape, the radius of curvature of the inner edge M2 is not particularly limited, but is preferably equal to or larger than the radius of curvature of the outer edge M1. The shape of the bulge of the inner edge M2 is preferably an arc shape.

As described above, the thickness of the permanent magnet M is largest at the location of the center C of the magnetic pole along the circumferential direction. Preferably, the thickness of the permanent magnet M is greatest in the center C of the magnetic pole and decreases monotonically outward on both sides in the circumferential direction. In the case that the permanent magnet M has a plano-convex shape or a biconvex shape symmetrical to the center axis C, the thickness of the permanent magnet M is largest at the center C of the magnetic pole, and decreases monotonically outward on both sides in the circumferential direction. The thickness of the permanent magnet refers to a geometric thickness along a direction of the center axis C as described above, regardless of a position of the permanent magnet M in the circumferential direction.

It is preferred that an opening angle θ _M (center angle of the outer edge M1 with respect to the rotation axis O) of the permanent magnet M is substantially equal to an opening angle θ _S (center angle of the inner peripheral surface 21c of the teeth 21b with respect to the rotation axis O). Thus, as will be described later, an excellent effect of reducing the cogging torque can be exerted. In particular, the opening angle θ _M of the permanent magnet M is preferably in a range of ± 10% with respect to the opening angle (θ _S ) of the stator 20 (0.90 ≤ θ _M /θ _S ≤ 1.10). The opening Angle of the permanent magnet M is more preferably in a range of ±5%, more preferably in a range of ±2% with respect to the opening angle of the stator 20.

Shape and magnetization orientation of the permanent magnet, and characteristics of the motor

In the motor 1 according to the present embodiment, as described above, the permanent magnet M has a centrally thickened shape with a uniform gap, in which the outer edge M1 has an arc shape centered on the rotation axis O of the rotor 10, and the inner edge M2 has an arc shape centered on the inside in the radial direction has a more protruding shape than an arc shape centered on the rotation axis O of the rotor 10, and the thickness is greatest at the center C of the magnetic pole. The magnetization direction of the permanent magnet M has a concentrated orientation. Due to the effect of the shape and magnetization direction of the permanent magnet M, it is possible to reduce a cogging torque and prevent the demagnetization of the permanent magnet M while at the same time maintaining a high torque of the motor 1.

A center-thickened shape permanent magnet in which a center portion is thick is used in a conventional motor, but as in a motor 1' according to an aspect of the prior art as shown in FIG 3 shown, the outer edge m1 of a permanent magnet m does not have an arc shape centered on the axis of rotation O of the rotor 10, but rather an arc shape that has a smaller radius of curvature than that. Document 1 also discloses a permanent magnet having such a shape. In this case, because the arc shape of the inner peripheral surface 21c of the teeth 21b of the stator core 21 and the arc shape of the outer edge m1 of the permanent magnet m are not concentric with each other, a distance of the air gap G between the permanent magnet m and the stator core 21 along the circumferential direction does not become the same, but the air gap G becomes wider from the point of the center axis C outwards in the circumferential direction (by the double arrow in 3 indicated). That is, the shape of the permanent magnet m can be referred to as a center-thickened shape with an uneven gap. Further in particular, the permanent magnet m has an in 3 Aspect shown has a linear inner edge m2, and can be described as plano-convex with an uneven gap.

In this way, in a case where the permanent magnet m has a center thickened shape with an uneven gap, when the magnetization direction in the entire area of the permanent magnet m is set parallel to the center axis C (parallel orientation), as shown by the simple arrow in 3 indicated, a waveform (waveform obtained by a soft iron core without a slot in place of the stator 20; the same applies hereinafter) of the magnetic flux density generated in the air gap close to a sine wave is obtained, and the cogging torque can be reduced to a small value. This is because, in general, if the thickness of the permanent magnet along the magnetization direction is denoted as I _m and the distance of the air gap along the magnetization direction is denoted as I _g , the magnetic flux density at each location of the air gap along the circumferential direction is represented by a value I _m /I _g is represented; but, as in 3 shown, in the case that the permanent magnet m is aligned in parallel and has a center thickened shape with an uneven gap, the distribution is such that I _g decreases along the circumferential direction towards the center C of the permanent magnet m and I _m increases, and the Value I _m /I _g varies gradually over the entire area of the permanent magnet m (see model 1 of 5A) .

However, in the case that the permanent magnet m has a center-thickened shape with an uneven gap, the permanent magnet m is further away from the stator 20 in the circumferentially outward region, and the magnetic flux of the permanent magnet m cannot be efficiently used as the magnetic flux of the air gap . In other words, the operating point of the permanent magnet m lies in a region of low magnetic flux density. The magnetic flux that is not used as the magnetic flux of the air gap becomes a magnetic leakage flux (see 4A) and does not contribute efficiently to producing torque. Therefore, it is difficult to obtain high torque.

In the case that the permanent magnet M is designed to have a center thickened shape with a uniform gap, in which the outer edge M 1 has an arc shape centered on the rotation axis O of the rotor 10, as in the motor 1 according to the present embodiment, instead a center-thickened shape with an uneven gap, the air gap G can be shortened and the permanent magnet M can be brought closer to the stator 20, even in the circumferentially outer region of the permanent magnet, similar to the center region. As a result, the magnetic leakage flux is reduced (see 4B) , and the magnetic flux of the permanent magnet M can be efficiently called the magnetic flux of the air gap be used. In other words, the operating point of the permanent magnet M can be placed in a region of high magnetic flux density. The torque of the motor 1 can thus be increased. The amount of permanent magnet M required to cover the required torque can be reduced compared to the case where a permanent magnet m having a center-thickened shape and an uneven gap is used. According to experimental calculations in the example to be described later, the same torque can be obtained even if the amount of the permanent magnet M is reduced by 16% compared to the case where a permanent magnet m having a center-thickened shape and an uneven gap is used.

In this way, by using a permanent magnet M with a thickened center shape and a uniform gap, the torque can be improved. However, in the case that magnetization in parallel orientation is applied to the permanent magnet M having a center-thickened shape with a uniform gap, the cogging torque may become higher than in the case of 3 , in which the permanent magnet has a thickened center shape with an uneven gap. This is because, as described above, the magnetic flux density at each point of the air gap G is given by the value of I _m /I _g ; but in the case that the permanent magnet M with a center-thickened shape and a uniform gap is used, the gap I _g of the air gap is the same in the entire area of the permanent magnet M in the circumferential direction, and thus the magnetic flux density is substantially determined by the thickness I _m of the permanent magnet M given. That is, the waveform of the magnetic flux density in the air gap G varies only gently from the location at the center C of the magnetic pole to a location corresponding to the dimension of the permanent magnet M in the circumferential direction, but varies sharply at a location distant from the location which corresponds to the dimension of the permanent magnet M in the circumferential direction, and has a shape close to a rectangular shape (see Model 3 in 5A) .

Therefore, the magnetization direction applied to the permanent magnet M with a center-thickened shape and a uniform gap is not the parallel orientation but the concentrated orientation, whereby the waveform of the magnetic flux density in the air gap G can be made close to a sine wave, and the cogging torque can be reduced. As described above, the waveform of the magnetic flux density in the air gap is given by the value I _m /I _g , but the distance I _g of the air gap G and the thickness I _m of the permanent magnet M, which determine this value, are related to the direction along the magnetization direction, and by applying the concentrated orientation of the permanent magnet M having a center-thickened shape with a uniform gap, an inclination angle of the magnetization with respect to the center axis C increases with the distance from the center axis C outward in the circumferential direction, and the value of I _m becomes larger than the actual thickness of the permanent magnet M. Because the volume V _m of the permanent magnet M does not change even if the inclination angle of magnetization changes, V _m = I _m × S _m is maintained when the cross-sectional area of the magnet is denoted by S _m becomes. That is, by tilting the magnetization orientation, the magnetic flux density at the operating point I _m /I _g increases, but an equivalent magnet cross-sectional area S _m (area of an end surface of the permanent magnet M perpendicular to the magnetization direction) decreases. For a magnet that is concentratedly aligned, the decrease in the equivalent magnet cross-sectional area S _m of the permanent magnet M is greater than the increase in the value I _m /I _g due to the displacement from the location of the center axis C in the circumferential direction, and the magnetization orientation varies continuously with the distance from the position of the center axis C in the circumferential direction, and thus the magnetic flux density in the air gap G gradually varies and decreases, and a distribution close to a sine wave is obtained. Thus, the waveform of the magnetic flux density in the air gap G becomes more close to a sine wave than in the case where parallel alignment is applied, and the cogging torque is reduced.

In this way, by using the permanent magnet M having a center thickened shape with a uniform gap and concentrated alignment, it is possible to improve the torque and avoid an increase in the cogging torque as compared with the case where a permanent magnet having a center thickened shape with an uneven gap is used. When the convex portion 11a is provided on the rotor core 11, it is possible to exert a greater torque increasing effect by efficiently utilizing the magnetic flux. The reason is that the magnetic flux of the concentrated orientation permanent magnet M is easily directed in a direction connecting the permanent magnet M and the teeth 21b of the stator core 21, and an air-filled space in a magnetic flux path can be reduced.

When the concentrated alignment is applied, it is possible to exert an effect of preventing demagnetization of the permanent magnet M by forming the permanent magnet in a center-thickened shape. The higher the permeance coefficient, the less likely this is Demagnetization of the permanent magnet M, and the greater the thickness I _m of the permanent magnet M becomes along the magnetization direction, the greater the permeance becomes. That is, in a case where the permanent magnet is concentratedly aligned, the effect of preventing demagnetization due to an increase in permeance outward in the circumferential direction where the magnetization direction is strongly inclined is stronger, whereas demagnetization is more likely in a circumferential area occurs close to the central axis C. However, the permanent magnet M is shaped to have a center-thickened shape in which the inner edge M2 protrudes more inwardly in the radial direction than an arc centered on the rotation axis O, and the thickness (thickness as actual extent) of the permanent magnet M in the The center in the circumferential direction is raised, which can prevent demagnetization. In this way, the demagnetization of the entire permanent magnet M is counteracted both by the effect of increasing the permeance coefficient in the outer region in the circumferential direction due to the application of the concentrated orientation, and by the effect of preventing demagnetization in the central region due to the centrally thickened shape . In the case that the permanent magnet M has a plano-convex shape, and more so, when it has a biconvex shape, it is possible to achieve a large demagnetization preventing effect by ensuring the thickness at the center region.

As described above, when the permanent magnet M is employed in a center thickened shape with a uniform gap, the cogging torque is reduced by the magnetization orientation being a concentrated orientation, and further by the opening angle of the permanent magnet being close, for example, within a range of about ±10%, at the opening angle of the stator 20 is set, the effect of reducing the cogging torque is further enhanced. When the rotor 10 rotates with respect to the stator 20, the permanent magnet M receives a torque in the direction of attraction in the direction of rotation from the tooth 21b located at the front in the direction of rotation, and receives a torque in the direction of retraction in a direction opposite to the direction of rotation through the tooth 21b, which is located at the rear in the direction of rotation. Although the torques in the two directions affect the torque waveform of the motor 1, in the case that the opening angle of the permanent magnet M is equal to the opening angle of the stator 20, the torque waveform is likely to become a continuous waveform depending on the rotation angle balancing the torques in both directions. That is, the contribution of a high-frequency waveform component to the torque is reduced and the cogging torque is reduced.

Example

The present invention is described below using examples. This verified how the characteristics of the motor change depending on the shape and magnetization orientation of the permanent magnet.

< 1 > Comparison with aspects of the prior art

First, characteristics of a motor were compared between a case in which a permanent magnet had a plano-convex shape with a non-uniform gap and the magnetization was aligned in parallel as in the prior art aspect 3 , and a case in which a permanent magnet had a plano-convex shape with a uniform gap and the magnetization was concentratedly aligned as in the embodiment of the present invention 1 and 2 .

Analysis method

As Model 1, as in 3 shown, a model was created in the SPM motor in which a permanent magnet had a plano-convex shape with an uneven gap and the magnetization in a parallel orientation. The configurations of the rotor core, stator, and protection tube were the same as those in 1 shown. As Model 2, compared to Model 1, only the shape of the permanent magnet and the magnetization orientation were changed, resulting in a model as in 1 and 2 shown was produced, in which a permanent magnet had a plano-convex shape with a uniform gap and concentrated magnetization orientation. A model was created as Model 3 in which the lumped orientation of Model 2 was changed to a parallel orientation.

The simulation was carried out on each model to analyze the magnetic flux density distribution and torque characteristics. The simulation was carried out by electromagnetic field analysis using a finite element method (FEM).

The parameters used in the simulation are summarized in the following Table 1 for Model 1. For the magnet dimensions given in Table 1, W denotes a width of the permanent magnet (ie, a dimension in a direction perpendicular to the center axis), t denotes a thickness of the permanent magnet (ie, thickness at the center of the magnetic pole), and L denotes a length of the permanent magnet (ie, dimension along the axis of rotation of the rotor). Two aspects were carried out as simulations on models 2 and 3, namely a first aspect in which the volumes of the permanent magnets were the same and a second aspect in which the maximum torques were the same, starting from model 1. Regarding the magnet dimensions of the Models 2 and 3 were used W = 11.20 mm and t = 1.90 mm in the aspect where the volumes were equal. On the other hand, in the aspect where the maximum torque was equal, W = 9.20 mm and t = 1.85 mm were used. In each model, the opening angle of the permanent magnet and the opening angle of the stator were adjusted to the same value. The alignment angle of the lumped alignment in model 2 was set to 70°. Table 1 Analysis conditions 2D transient response analysis (JMAG Designer ver.20.2) wiring ΔWiring Kitchen sink convolutions 17 turns/slot Resistance value 0.025Ω/line Wires Parallel Rotor dimensions ▪Outer diameter: 40 mm ▪Laminate thickness: 43 mm Stator dimensions ▪Inner diameter: 41mm ▪Outer diameter: 77 mm ▪Laminate thickness: 43 mm Magnet dimensions W 9.1mm × t 2.4mm × L 43.0mm Maximum current 100 Arms gap length 0.5mm

Analysis results

4A and 4B show magnetic flux density distributions of Model 1 and Model 2, in which the volumes of the permanent magnets were set equal. As in 4A As shown, in the case where the parallel alignment was applied to a permanent magnet having a plano-convex shape and an uneven gap, as enclosed by a broken line, a magnetic flux is emitted at the end portion of the permanent magnet toward the permanent magnet side, and a leakage magnetic flux is generated . On the other hand, as in 4B shown that in the case where concentrated alignment was applied to a permanent magnet with plano-convex shape and uniform gap, no magnetic leakage flux of the permanent magnet was observed. As enclosed by a dashed line, the magnetic flux extends toward the stator even at the end portion of the permanent magnet, and is an effective magnetic flux that contributes to generating torque. In this way, it is obvious that a proportion of the effective magnetic flux in the case of model 2 is larger than in the case of model 1, and a high torque is obtained.

5A Fig. 1 shows each air gap magnetic flux density waveform (waveform obtained when the stator is a soft iron core without a slot) of models 1 to 3 in the case that the volumes of the permanent magnets are equal. Accordingly, the magnetic flux density waveform in Model 1, in which parallel alignment was applied to a permanent magnet with a plano-convex shape and non-uniform gap, has a smooth mountain-like distribution close to a sine wave. On the other hand, in Model 3, in which a permanent magnet was changed to a plano-convex shape with a uniform gap while maintaining the parallel orientation, a magnetic flux density waveform far deviating from a sine wave and approaching a square wave is obtained. In model 2, in which the concentrated alignment is on a permanent magnet with a plano-convex shape and uniform gap was applied, a magnetic flux density waveform closer to a sine wave is obtained compared to Model 3, although it does not reach the waveform of Model 1. That is, it can be shown that the waveform of the magnetic flux density in the air gap becomes a sine wave by changing the orientation of the magnetization from the parallel orientation to a concentrated orientation for a permanent magnet with a plano-convex shape and a uniform gap. The sine wave of the magnetic flux density waveform leads to a reduction in the cogging torque.

In 5A When the waveform of Models 2 is compared with the waveform of Model 1 in more detail, the magnetic flux density in the peak area is not significantly changed, but the magnetic flux density in Model 2 is larger in areas on either side of the peak area. Although 5B shows each amplitude of a fundamental wave component of the air gap magnetic flux density for each model (amplitude of model 1 is 1), the amplitude of the fundamental wave component in model 2 is 8% larger than that in model 1, and the difference in magnetic flux density in the in 5A The waveform under consideration is quantitatively confirmed. In this regard, the fact that the magnetic flux density in Model 2 is larger than in Model 1 corresponds to the fact that a ratio of the effective flux density in Model 2 is larger than when comparing the magnetic flux density distributions of 4A and 4B , and suggests that high torque is obtained in Model 2.

6A and 6B show a comparison of the maximum torques obtained for models 1 to 3 and the cogging torques in the case that the volumes of the permanent magnets were the same. In each case, the value for Model 1 was normalized to 1. In 6A the value of the maximum torque of Model 2 is 7% larger than that of Model 1. This corresponds to the fact that a proportion of the effective magnetic flux is larger in Model 2, as can be seen from the comparison of the magnetic flux density distributions in 4A and 4B and comparing the magnetic flux density waveforms of 5A visible. Model 3 also achieves a high maximum torque similar to Model 2.

Regarding the value of the cogging torque in 6B the cogging torque of Model 3 is significantly increased, to 30 times or more that of Model 1. On the other hand, the cogging torque of Model 2 is six times or less that of Model 1, and is increased by a smaller amount than that of Model 3. This corresponds to the finding that as a waveform of the magnetic flux density in 5A for model 2 a waveform closer to a sine wave is obtained than for model 3.

In this way, it can be seen that when comparing models 1 to 3, in the case where the volumes are equal, the torque is improved thanks to the increase in the effective magnetic flux by changing the permanent magnets from plano-convex shape with uneven gap to plano-convex shape with uniform gap becomes. Further, it can be seen that by applying the concentrated orientation as opposed to parallel orientation to a permanent magnet having a plano-convex shape with a non-uniform gap, the magnetic flux in the air gap approaches a sine wave and the cogging torque can be reduced, although not as much as in the case of a plano-convex one Shape with uneven gap.

From the previous analysis for the case where the volumes of the permanent magnets are equal, it is clear that a high torque can be obtained by using a permanent magnet with a plano-convex shape and a uniform gap; and even if the volume is reduced, an equivalent torque can be obtained, as in the case where a permanent magnet having a plano-convex shape with an uneven gap is used. Next, the analysis results are compared in the case where the maximum torques of models 1 to 3 were equated by changing the volumes of models 2 and 3. The volumes of the permanent magnets of models 2 and 3 with a plano-convex shape with a uniform gap are 16% smaller than the volume of the permanent magnet of model 1 with a plano-convex shape and an uneven gap.

7A and 7B show the comparison of the maximum torques and cogging torques in the three models in the case that the maximum torques were the same. The maximum torques in 7A are essentially equal to 1 for the three models, and it is confirmed that the maximum torques are the same as intended by adjusting the volumes of the permanent magnets. Regarding the cogging moments in 7B The cogging torque of Model 3 is 13.1 times that of Model 1, which is a significantly higher value, whereas the cogging torque of Model 2 is increased by 72%, a value twice or less than that of Model 1.

From the above, it is confirmed that by forming the permanent magnet into a plano-convex shape with a uniform gap, the same torque can be obtained even if the volume of the permanent magnet is reduced by 16% compared to the case of the plano-convex shape with an uneven gap. In the case that the magnetization orientation applied to the permanent magnet having a plano-convex shape with a uniform gap is a concentrated orientation, the cogging torque can be significantly reduced compared to the case of the parallel orientation, and can be increased to about 70% compared to that The case can be set in which the parallel alignment is applied to a permanent magnet with a plano-convex shape and an uneven gap. In this way, by forming a permanent magnet into a plano-convex shape with a uniform gap and applying the concentrated orientation, it is possible to maintain a high torque while reducing a cogging torque.

<2> Differences depending on the shape of the inner edge According to the above test in <1>, it is clear that it is possible to maintain a high torque and reduce a cogging torque by adopting a plano-convex shape with a uniform gap, with the outer edge of the permanent magnet has an arc shape centered on the axis of rotation of the rotor. Next, it was verified how the characteristics of the engine change in the case that the shape of the inner edge is changed when the outer edge has such an arc shape.

Analysis method

As an analysis model, as in 8A , 8B and 8C shown, three Morelle created in which the permanent magnet is in 8A Arch shape shown, a plano-convex shape (with a uniform gap) as in 8B shown, or a biconvex shape (with a uniform gap) as in 8C shown. The model for the plano-convex shape case was the same as Model 2 used in the above analysis of <1>, and the shape of the permanent magnet was modified from Model 2 in the arc shape and biconvex shape cases. A width W of the permanent magnet of 9.20 mm was set for all three models. This width corresponds to a width at which the opening angle of the permanent magnet is equal to the opening angle of the stator. The thickness t of the permanent magnet was given the arc shape of 8A set to 2.07 mm, with the plano-convex shape of 8B to 2.16 mm and with the biconvex shape of 8C to 2.34 mm. Due to the difference in thickness, the volumes of the permanent magnets are the same in all three cases. In the case of the biconvex shape, the radius of curvature of the inner edge was set to the same radius of curvature as that of the outer edge.

Regarding the above models in which the shape of the permanent magnet was changed to three shapes, the simulation was carried out using the same method as the analysis in <1> above with respect to the characteristics of the motor. As the magnetization orientation of the permanent magnet, two orientations, namely the concentrated orientation and the parallel orientation, were used. In each model, the alignment angle was set to 70° in the concentrated alignment.

Analysis results

9A and 9B show respective amplitudes of the maximum torque and the cogging torque in the case that the concentrated orientation and the parallel orientation were applied to the three shapes of the permanent magnet. In each case, the value obtained for model 1 of the test <1>, that is, the aspect of the prior art in which parallel alignment is applied to a plano-convex structure with a non-uniform gap, was normalized to 1.

Comparing the maximum torque in 9A A maximum torque exceeding that obtained according to the prior art aspect is obtained regardless of whether the permanent magnet had an arc shape, a plano-convex shape, or a biconvex shape. Since the volume of the permanent magnet was different from that according to the prior art aspect, the value of the maximum torque has no particular meaning, but it was confirmed that, from the viewpoint of comparison with the case of a plano-convex shape with an uneven gap, Even if the shape of the permanent magnet was changed from the plano-convex shape with a uniform gap, which was examined in detail in the analysis of <1>, to an arc shape or a biconvex shape with a uniform gap, a high torque of the same magnitude as in the case of the plano-convex shape with an even gap is obtained. If the maximum torques of the three forms are compared with each other The three shapes, in order from the higher torque, are the biconvex shape, the plano-convex shape, and the arc shape, although the differences are small. When the concentrated alignment and the parallel alignment are compared, in the case of the plano-convex shape and the biconvex shape, a slightly higher torque is obtained for the concentrated alignment.

If the cogging torques are in 9B are compared, there is a big difference in behavior between an arc shape and the case of the plano-convex shape and the biconvex shape. No matter whether the concentrated orientation or the parallel orientation was applied, the cogging torque in the case of the arc shape was five times or more than that in the prior art aspect. On the other hand, the cogging torque in parallel orientation in the case of the plano-convex shape or the biconvex shape was significantly increased to 12 times or more compared to the prior art aspect, but in the concentrated orientation, the cogging torque was reduced to a level below that of the prior art aspect Technology reduced. From this result, it can be seen that by shaping the shape of the permanent magnet into a center-thickened shape such as a plano-convex shape or a biconvex shape in which the inner edge protrudes toward the inside in the radial direction more than an arc shape centered on the rotation axis of the rotor, and the magnetization direction is one concentrated alignment, a great effect of reducing the cogging torque can be exerted. In particular, by adopting a biconvex shape in which the thickness at the center portion is relatively large, the effect of reducing the cogging torque is enhanced. The values of maximum torque and cogging torque in the case of the plano-convex shape are different from those of Models 2 and 3 in the Figure 1 due to the difference in magnet dimensions 6A and 6B analysis shown under < 1 >.

Show next 10A until 10C Distributions of the permeance coefficient in the cases where concentrated alignment was applied to the three permanent magnets, respectively. Also shows 10D the distribution of the permeance coefficient in the case where the parallel alignment was applied to a permanent magnet according to the aspect of the prior art, namely a permanent magnet having a plano-convex shape with a non-uniform gap. The smaller the permeance coefficient, the smaller the demagnetization resistance at that position, and the more likely demagnetization occurs there.

With the aspect of the prior art as in 10D shown, no significant non-uniform distribution of the permeance coefficient is formed in a region on the inside (lower side of the drawing) of the permanent magnet in the radial direction. However, in each of the three aspects where the concentrated focus of 10A until 10C was applied, a region is formed in which the permeance coefficient is locally smaller than that on the circumference, namely in the inner region of the permanent magnet in the radial direction, as shown by the dashed line in 10A indicated. These areas are prone to demagnetization. When the three aspects are compared, the permeance coefficient is in 10A , in which the permanent magnet has an arc shape, is small in an inner region in the radial direction (1.44 in the center region), and the localization of the small permeance coefficient region is strong. Therefore, demagnetization of the permanent magnet easily occurs in the center region. Compared to 10A is in the case of the plano-convex shape of 10B the permeance coefficient in the inner region is slightly larger in the radial direction (1.52 in the central region), and the localization of the region with small permeance coefficient is also more extensive. In the case of a biconvex shape of 10C the permeance coefficient in the inner region is even larger in the radial direction (1.74 in the central region), and the localization of the region with a small permeance coefficient is even more extensive. From these results, it can be seen that the local lowering of the permeance coefficient in the inner region in the radial direction in the order of biconvex shape, plano-convex shape and arc shape is unlikely to occur, and the demagnetization can be prevented.

As described above, in the case that an outer edge of the permanent magnet has an arc shape centered on the rotation axis of the rotor, the cogging torque can be reduced while a high torque can be ensured by adopting a center thickened shape in which an inner edge has a shape which protrudes further inward than an arc shape centered on the rotation axis of the rotor, and a center portion of the permanent magnet is thick, and further wherein a concentrated orientation is applied. The demagnetization of the permanent magnet can also be reduced to a small value. If a biconvex shape is adopted in which the thickness in the central region is particularly large, particularly strong effects in increasing the torque, reducing the cogging torque and preventing demagnetization can be achieved.

<3> Relationship between opening angles of permanent magnet and stator Finally, how a relationship between the opening angle of the permanent magnet and the opening angle of the stator influences the characteristics of the motor was investigated.

Analysis method

The maximum torque and the cogging torque were estimated by the same simulation as in <1>, where the opening angle (opening angle of the outer edge) of the permanent magnet used in the analysis of <1> was based on model 2 (with the permanent magnet with a plano-convex shape and a uniform gap ; concentrated orientation) was changed. The thickness t of the permanent magnet was set to 1.85 mm, and the width W was changed according to the opening angle. The opening angle of the stator (opening angle of an inner circumferential surface of the teeth) was set. The alignment angle of the concentrated alignment was set to three angles 60°, 65° and 70°.

Analysis results

11A and 11B show a relationship between an opening angle ratio (ratio of the magnet opening angle θ _M to the stator opening angle θ _S ; θ _M /θ _S ) and the maximum torque, or a relationship between the opening angle ratio and the cogging torque. In any case, the value obtained in Model 1 of Test <1>, that is, the aspect of the prior art in which parallel alignment was applied to a permanent magnet with a plano-convex shape and a non-uniform gap, is normalized to 1.

In 11A the maximum torque increases monotonically with the opening angle ratio. The reason for this is that the volume of the permanent magnet increases with the opening angle ratio. On the other hand, the cogging torque in 11B a minimum at the point where the opening angle ratio is 1 (more precisely 0.99). That is, it can be seen that when the opening angle of the permanent magnet becomes equal to the opening angle of the stator, the cogging torque is reduced the most. This behavior occurs regardless of the orientation angle of the concentrated orientation.

In a range where the opening angle ratio is ±10% around the minimum, the cogging torque can be reduced to 25 times or less that in the prior art aspect. This level is lower than that of the in 6B Model 3 shown, that is, the case in which the parallel alignment is applied to a permanent magnet with a plano-convex shape with a uniform gap. Further, in a range of the opening angle ratio of ±5% or ±2% around the minimum, the cogging torque can be reduced to 15 times or less or 10 times or less that in the prior art aspect.

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

The present application is based on Japanese Patent Application No. 2022-091281 , filed June 6, 2022, and the contents thereof are incorporated herein by reference.

1

Motor (rotating electric machine)

10

rotor

11

Rotor core

11a

convex area

20

stator

21

Stator core

21a

Posterior yoke area

21b

Tooth

21c

Inner circumferential surface of the teeth

22

Kitchen sink

30

protective tube

40

Wave

C

Center of the magnetic pole (center axis)

G

air gap

M

Permanent magnet

M1

Outer edge

M2

Inside edge

M3

Circumferential edge

O

Axis of rotation of the rotor

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2019/069539 A1 [0002]
• JP 2020191692 A [0002]
• JP 2022091281 [0069]

Claims (6)

Rotating electric machine (1), comprising: a stator (20) which has: a stator core (21) having a hollow cylindrical shape and a plurality of teeth (21b) and a hollow portion; and coils (22) wound around the respective teeth (21b); and a rotor (10) which is arranged in the hollow region of the stator core (21) and has: a rotor core (11) having an outer peripheral surface; and a plurality of permanent magnets (M) attached to the outer peripheral surface of the rotor core (11) and each representing a magnetic pole, each of the teeth of the stator core (21) having an inner peripheral surface, the inner peripheral surface (21c) of the teeth (21b) of the stator core (21) has an arcuate shape centered on the rotation axis (O) in a cross section perpendicular to the rotation axis (O) of the rotor (10), and each of the permanent magnets (M) of the rotor (10), independently for each of the magnetic poles, has a centrally thickened shape, in which an outer edge of the permanent magnet (M) on the outside in the radial direction of the rotor (10) is centered on the axis of rotation (O). Has an arc shape, an inner edge of the permanent magnet (M) on the inside in the radial direction of the rotor (10) has a shape that projects to the inside in the radial direction of the rotor (10) more than an arc shape centered on the axis of rotation (O), and one Thickness between the outer edge of the permanent magnet (M) and the inner edge of the permanent magnet (M) is greatest at a point in the center (C) of the magnetic pole, and each of the permanent magnets (M) of the rotor (10) has a concentrated orientation in which a magnetization direction is inclined in a direction towards the center (C) of the magnetic pole on the outside in the radial direction of the rotor (10), namely outwardly along a Circumferential direction of the rotor (10) increasing. Rotating electrical machine (1) according to Claim 1 , wherein the inner edge (M2) of the permanent magnet (M) is linear in cross section perpendicular to the axis of rotation (O) of the rotor (10). Rotating electrical machine (1) according to Claim 1 , whereby the inner edge of the permanent magnet (M) bulges towards the inside in the radial direction of the rotor (10). Rotating electrical machine (1) according to one of Claims 1 until 3 , further comprising: a protective tube (30) on the outer circumference of the rotor (10), the protective tube (30) having a cylindrical shape and being formed of a non-magnetic material, the outer edge of the permanent magnet (M) being along the inner peripheral surface of the Protective tube (30) extends. Rotating electrical machine (1) according to one of Claims 1 until 3 , wherein an opening angle (θ _M ) of the outer edge of the permanent magnet (M) with respect to the rotation axis (O) is within a range of ±10% with respect to the opening angle (θ _S ) of the inner peripheral surface (21c) of the teeth (21b) in Reference to the axis of rotation (O). Rotating electrical machine (1) according to one of Claims 1 until 3 , wherein in the rotor (10), the rotor core (11) has a convex region (11a) between the adjacent magnetic poles, the convex region (11a) being in contact with the permanent magnets (M) on both sides and facing the outside in the Radial direction of the rotor (10) projects further than the inner edge (M2) of the permanent magnet (M).

Images