Permanent magnet motor

Abstract

This invention provides a permanent magnet motor. It can improve the output per unit volume. The permanent magnet motor (1) has a pair of first permanent magnets (5) for each magnetic pole inside the rotor (2) and a second permanent magnet (6) located between the pair of first permanent magnets (5). A first gap (7) is provided at the radially outer end of each first permanent magnet (5), and a second gap (8) is provided at both ends of each second permanent magnet (6). A first magnetic path (9) communicating with the teeth (3) of the stator (4) is divided between each adjacent first gap (7), and a second magnetic path (10) is divided between each adjacent first gap (7) and second gap (8). When the opening angles of the first and second magnetic paths (9, 10) centered on the rotation axis (A) are set to α and β, and the opening angle of the magnetic path passing through the teeth is set to γ, an outer peripheral hole (12) is provided to satisfy the relationship α < β and the opening angle β is close to the opening angle γ.

Description

Technical Field

[0001] This invention relates to permanent magnet electric motors. Background Technology

[0002] Previously, there was a known permanent magnet motor that had a rotor and a stator, wherein the stator was provided with inward teeth that were opposed to the outer periphery of the rotor to form a rotating magnetic field (see, for example, Patent Documents 1 and 2).

[0003] In the permanent magnet motor of Patent Document 1, inside the rotor, a pair of first permanent magnets and second permanent magnets are provided for each magnetic pole, wherein the pair of first permanent magnets are configured in a V-shape that opens radially outward; the second permanent magnets are arranged along the outer periphery of the rotor between the radially outer ends of the first permanent magnets.

[0004] A first gap is provided at the radially outer end of each first permanent magnet, and a second gap is provided at both ends of each second permanent magnet. The first gap and the second gap respectively divide the first magnetic circuit and the second magnetic circuit. The first magnetic circuit is connected to each tooth between each adjacent first gap; the second magnetic circuit is connected to each tooth between each adjacent first gap and second gap.

[0005] Furthermore, by setting the width w1 of the first magnetic circuit to be greater than or equal to the width w2 of the second magnetic circuit (w1≥w2), the reluctance torque can be increased, resulting in high torque and high rotational drive.

[0006] On the other hand, in the permanent magnet motor of Patent Document 2, a flux blocking section is provided circumferentially on the outer periphery of the rotor. This flux blocking section blocks the closed-loop flux generated around the armature winding. The flux blocking section has multiple non-magnetic body parts, which are located between adjacent permanent magnets on the outer periphery of the rotor and extend radially. The multiple non-magnetic body parts are configured to extend from the outer periphery to the inner periphery of the rotor, and their lengths decrease sequentially from the d-axis toward the q-axis.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-229395

[0010] Patent Document 2: Patent No. 6002217 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the permanent magnet motor of Patent Document 1, torque is generated by the magnetic lines of force entering the teeth through the first magnetic circuit and the second magnetic circuit, but the relationship between the first magnetic circuit, the second magnetic circuit and the teeth is not disclosed at all. Therefore, it can be considered that there is room for improvement in the torque (output per unit volume) regarding the relationship between the first magnetic circuit, the second magnetic circuit and the teeth.

[0013] Furthermore, in the permanent magnet motor according to Patent Document 2, the magnetic circuit between adjacent permanent magnets becomes narrow due to the presence of multiple non-magnetic parts, resulting in magnetic saturation on the rotor core, thus causing significant losses. Therefore, there is room for improvement in increasing the torque of the permanent magnet motor.

[0014] The object of the present invention is to improve the output per unit volume in a permanent magnet motor in view of the problems existing in the prior art.

[0015] Methods for solving problems

[0016] The permanent magnet motor of the present invention includes a rotor and a stator. The stator is provided with a plurality of inward-facing teeth, which are opposed to a plurality of positions on the outer periphery of the rotor to form a rotating magnetic field.

[0017] As viewed from a cross-section perpendicular to the rotor's axis of rotation, inside the rotor, for each magnetic pole, are arranged a pair of first permanent magnets and a second permanent magnet, wherein the pair of first permanent magnets are configured in a V-shape or U-shape opening radially outward of the rotor; the second permanent magnet is arranged along the outer periphery of the rotor between the radially outward ends of the pair of first permanent magnets in the circumferential direction of the rotor.

[0018] A first gap is provided at the radially outer end of each of the first permanent magnets inside the rotor, and a second gap is provided at both ends of each of the second permanent magnets.

[0019] A first magnetic path communicating with the tooth is defined between each adjacent first gap, and a second magnetic path communicating with the tooth is defined between each adjacent first gap and second gap.

[0020] The permanent magnet motor is characterized in that...

[0021] The opening angle of the first magnetic circuit at the outer periphery of the rotor relative to the axis of rotation is set as α, the opening angle of the second magnetic circuit at the outer periphery of the rotor relative to the axis of rotation is set as β, the imaginary line connecting the magnetic circuit passing through the teeth with the shortest distance to the center of rotation on the side closest to the first permanent magnet in the circumferential direction is set as γ1, the imaginary line connecting the magnetic circuit passing through the teeth with the shortest distance to the center of rotation on the side closest to the second permanent magnet in the circumferential direction is set as γ2, and the opening angle of the imaginary lines γ1 and γ2 relative to the axis of rotation is set as γ.

[0022] An outer peripheral hole is provided between the first gap in the circumferential direction and the imaginary line γ1 to satisfy the relationship α < β and the opening angle β is close to the opening angle γ, and the second gap extends to connect with the imaginary line γ2.

[0023] According to the present invention, the opening angle β of the second magnetic circuit becomes close to the opening angle γ between the imaginary lines γ1 and γ2 on both sides of the magnetic circuit passing through the tooth due to the presence of the outer peripheral hole. Therefore, magnetic reluctance can be minimized as much as possible when the tooth is aligned with the second magnetic circuit, and magnetic reluctance can be maximized as much as possible when the tooth is misaligned with the second magnetic circuit.

[0024] Therefore, it is possible to maximize the reluctance torque of the rotor in the direction of rotation (specifically, the force that makes the magnetic lines of force as short as possible so that the teeth are aligned with the second magnetic circuit), thereby increasing the output per unit volume of the permanent magnet motor.

[0025] In this invention, as the structure when viewed from a cross-section perpendicular to the rotation axis of the rotor, the outer peripheral hole may have an elongated shape along the radial direction of the rotor and the elongated portion is grounded with the imaginary line γ1 and extends along the second magnetic circuit.

[0026] Therefore, due to the presence of an outer peripheral hole with a radially elongated shape, it is possible to efficiently utilize the magnetic flux that causes the magnetic path through the teeth to align with the teeth.

[0027] Furthermore, in this invention, it is preferred that when the magnetic circuit of one of the teeth is substantially merged with the second magnetic circuit of one of the second magnetic circuits on both sides of each of the second permanent magnets, the magnetic circuit of the other tooth is substantially merged with the second magnetic circuit of the other of the second magnetic circuits on both sides.

[0028] Therefore, when the magnetic circuit of one tooth and the magnetic circuit of another tooth are combined with the second magnetic circuits on both sides of the second permanent magnet, there are no narrow sections on the magnetic circuits from each second magnetic circuit to each tooth, so the magnetic flux can flow smoothly, thereby further improving the torque of the permanent magnet motor. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of the main parts of a permanent magnet motor according to an embodiment of the present invention.

[0030] Label Explanation

[0031] 1: Permanent magnet motor, 2: Rotor, 3: Tooth, 4: Stator, 5: First permanent magnet, 6: Second permanent magnet, 7: First gap, 8: Second gap, 9: First magnetic circuit, 10: Second magnetic circuit, 11, 11a, 11b: Magnetic circuit, 12: Outer peripheral hole. Detailed Implementation

[0032] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Figure 1 The figure shows the appearance of the main part of the permanent magnet motor according to one embodiment of the present invention, viewed from a cross-section perpendicular to the axis of rotation of the main part of the permanent magnet motor. In the same figure, the structure of the circumferential 1 / 4 portion (corresponding to the amount of two poles) is shown; the structure of the other 3 / 4 portions is the same.

[0033] As shown in the figure, the permanent magnet motor 1 has a rotor 2 and a stator 4 with multiple inward-facing teeth 3. The multiple teeth 3 are opposed to multiple positions on the outer periphery of the rotor 2 to form a rotating magnetic field.

[0034] As viewed from a cross-section perpendicular to the rotation axis A of the rotor 2, inside the rotor 2, for each magnetic pole of the rotor 2, there is a pair of first permanent magnets 5 and second permanent magnets 6. The first permanent magnets 5 are configured in a V-shaped or U-shaped shape that opens radially outward from the rotor 2. The second permanent magnets 6 are arranged along the outer periphery of the rotor 2 between the radially outer ends of the pair of first permanent magnets 5 in the circumferential direction of the rotor 2.

[0035] A first gap (flux barrier) 7 is provided at the radially outer end of each first permanent magnet 5 inside the rotor 2, and a second gap (flux barrier) 8 is provided at both ends of each second permanent magnet 6.

[0036] A first magnetic path 9 communicating with the toothed portion 3 is divided between each adjacent first gap 7 in the circumferential direction, and a second magnetic path 10 communicating with the toothed portion 3 is divided between each adjacent first gap 7 and second gap 8. It should be noted that, in this embodiment, the first gap 7 is divided into two holes between the outer periphery of the rotor 2 and the end of the first permanent magnet 5 closest to the first gap 7.

[0037] Here, the opening angle at the outer periphery of the rotor 2 centered on the rotation axis A in the first magnetic circuit 9 is set as α, and the opening angle at the outer periphery of the rotor 2 centered on the rotation axis A in the second magnetic circuit 10 is set as β. Furthermore, the imaginary line connecting the magnetic circuit 11 passing through the tooth 3 with the shortest distance to the rotation center in the circumferential direction on the side closest to the first permanent magnet 5 is set as γ1, and the imaginary line connecting the magnetic circuit 11 passing through the tooth 3 with the rotation center in the circumferential direction on the side closest to the second permanent magnet 6 in the circumferential direction is set as γ2. The opening angle between the imaginary lines γ1 and γ2 centered on the rotation axis A is set as γ.

[0038] Thus, an outer peripheral hole 12 is provided between the first circumferential gap 7 and the imaginary line γ1 to satisfy the relationship α < β and the opening angle β is close to the opening angle γ, and the second gap 8 extends to the position where it connects with the imaginary line γ2. It should be noted that, in this embodiment, the second gap 8 is divided into two holes between the imaginary line γ2 and the end of the second permanent magnet 6 that is closest to the imaginary line γ2.

[0039] Furthermore, as a structure viewed from a cross section perpendicular to the rotation axis A of the rotor 2, the outer peripheral hole 12 has an elongated shape along the radial direction of the rotor 2, and this elongated portion extends along the second magnetic circuit 10 in contact with the imaginary line γ1.

[0040] Furthermore, the permanent magnet motor 1 is configured such that when the magnetic circuit 11 of one tooth 3 is substantially merged with one of the magnetic circuits 10 of the second magnetic circuits 10 on both sides of each second permanent magnet 6, the magnetic circuit 11 of the other tooth 3 is simultaneously substantially merged with the other magnetic circuit 10 of the second magnetic circuits 10 on both sides. Figure 1 The following situation is illustrated: while the magnetic circuit 11a of one tooth 3 is substantially merged with the second magnetic circuit 10 of one side, the magnetic circuit 11b of the other tooth 3 is substantially merged with the second magnetic circuit 10 of the other side.

[0041] In this structure, the opening angle β of the second magnetic circuit 10 is close to the opening angle γ due to the presence of the outer peripheral hole 12. This opening angle γ is the angle between the imaginary lines γ1 and γ2 on both sides of the magnetic circuit 11 of the tooth 3. Therefore, the permanent magnet motor 1 has the following characteristics: when the rotor 2 rotates about the rotation axis A, the magnetic reluctance is small when the tooth 3 and the second magnetic circuit 10 are aligned, and the magnetic reluctance is large when the tooth 3 and the second magnetic circuit 10 are misaligned.

[0042] In other words, due to the presence of the outer peripheral hole 12, the circumferential width of the second magnetic circuit 10 facing the tooth 3 in the radial direction is narrowed. That is, when the tooth 3 and the second magnetic circuit 10 are aligned, the magnetic lines of force of the magnetic circuit between the tooth 3 of the stator 4 and the iron core of the rotor 2 pass in a straight and shortest manner. However, when the tooth 3 and the second magnetic circuit 10 are somewhat misaligned, the magnetic lines of force of the magnetic circuit between the tooth 3 and the iron core of the rotor 2 are bent.

[0043] In addition, the rotation of rotor 2 is achieved through magnetic torque and magnetic reluctance torque. Magnetic torque is generated by the attractive and repulsive forces between the poles of the rotating magnetic field formed by stator 4 and the magnetic poles of the first permanent magnet 5 and the second permanent magnet 6 of rotor 2.

[0044] The reluctance torque is generated by the attractive force of the rotating magnetic field of the stator 4 relative to the iron core (sudden pole) of the rotor 2. That is, the reluctance torque is generated by the force that makes the magnetic lines of force of the magnetic circuit between the teeth 3 of the stator 4 and the iron core of the rotor 2 the shortest possible, so that the iron core (magnetic circuit) and the teeth 3 are aligned in the same direction.

[0045] Therefore, by utilizing the reluctance characteristics of the outer peripheral hole 12, the reluctance torque can be maximized by aligning the second magnetic circuit 10 and the tooth 3 in a consistent manner. Consequently, the rotor 2 rotates with high torque due to the presence of this reluctance torque.

[0046] Furthermore, since the outer peripheral hole 12 has an elongated shape along the radial direction of the rotor 2 and is grounded with the imaginary line γ1 and extends along the second magnetic circuit 10, the reluctance torque can be utilized more efficiently.

[0047] Furthermore, when the magnetic circuit 11 of the tooth 3 on one side of the second permanent magnet 6 merges with the second magnetic circuit 10, the magnetic circuit 11 of the tooth 3 on the other side is also merged with the second magnetic circuit 10. In this case, with the second magnetic circuits 10 at two positions in the circumferential direction aligned with the two teeth 3 respectively, no narrow sections are generated on each magnetic circuit from the two second magnetic circuits 10 toward the magnetic circuits 11 of the two teeth 3. Therefore, the magnetic flux flows straight and smoothly between the second magnetic circuits 10 and the magnetic circuits 11 of the teeth 3. On the other hand, when the two teeth 3 are somewhat offset from each of the second magnetic circuits 10, the two sets of magnetic lines of force through the magnetic circuit bend together, maximizing the reluctance torque that causes the two second magnetic circuits 10 to be aligned with the two teeth 3. As a result, the rotor 2 rotates with a higher torque.

[0048] It should be noted that if a large magnetic shielding section (hole) is provided as the second gap section 8, the strength of the rotor 2 will decrease, thus lowering the upper limit of the rotational speed. As a result, even if the torque can be increased, the output (torque × speed) will not increase. In this regard, since the second gap section 8 is divided into two holes in the manner described above, the strength of the rotor 2 will not be reduced, thereby enabling the rotor 2 to rotate with high torque and high output.

[0049] As described above, according to this embodiment, since the opening angle β of the second magnetic circuit 10 is close to the opening angle γ between the imaginary lines γ1 and γ2 on both sides of the magnetic circuit passing through the tooth due to the presence of the outer peripheral hole 12, the magnetic reluctance torque in the rotation direction of the rotor 2 can be maximized, thereby improving the output per unit volume of the permanent magnet motor 1.

[0050] Furthermore, since the outer peripheral hole 12 has an elongated shape along the radial direction of the rotor 2 and is grounded along the second magnetic circuit 10, it can efficiently utilize reluctance torque.

[0051] Furthermore, the permanent magnet motor 1 is configured such that when the magnetic circuit 11 of one tooth 3 is combined with one of the magnetic circuits 10 on both sides of each second permanent magnet 6, the magnetic circuit 11 of the other tooth 3 is simultaneously combined with the other magnetic circuit 10 on both sides. Therefore, the magnetic flux can flow smoothly, thereby further improving the torque of the permanent magnet motor 1.

[0052] It should be noted that the present invention is not limited to the embodiments described above. For example, the second gap portion 8 and the outer peripheral hole portion 12 can also be subdivided by distributing multiple holes of different sizes in a grid pattern. This allows for a more effective increase in the torque and output of the permanent magnet motor 1 while preventing a decrease in the strength of the rotor 2.

Claims

1. A permanent magnet electric motor comprising a rotor and a stator, wherein the stator is provided with a plurality of inwardly facing teeth, the plurality of teeth being opposed to a plurality of positions on the outer periphery of the rotor for forming a rotating magnetic field. As viewed from a cross-section perpendicular to the rotor's axis of rotation, inside the rotor, for each magnetic pole, a pair of first and second permanent magnets are provided, wherein... The pair of first permanent magnets are configured in a V-shape or U-shape that opens radially outward toward the rotor; the second permanent magnet is disposed along the outer periphery of the rotor between the radially outward ends of the pair of first permanent magnets in the circumferential direction of the rotor. A first gap is provided at the radially outer end of each of the first permanent magnets inside the rotor, and a second gap is provided at both ends of each of the second permanent magnets. A first magnetic path communicating with the tooth is defined between each adjacent first gap, and a second magnetic path communicating with the tooth is defined between each adjacent first gap and second gap. The permanent magnet motor is characterized in that... The opening angle of the rotor of the first magnetic circuit at its outer periphery relative to the axis of rotation is set as α, the opening angle of the rotor of the second magnetic circuit at its outer periphery relative to the axis of rotation is set as β, the imaginary line connecting the magnetic circuit passing through the teeth with the shortest distance to the center of rotation on the side closest to the first permanent magnet in the circumferential direction is set as γ1, the imaginary line connecting the magnetic circuit passing through the teeth with the center of rotation on the side closest to the second permanent magnet in the circumferential direction is set as γ2, and the opening angle of the imaginary lines γ1 and γ2 relative to the axis of rotation is set as γ. An outer peripheral hole is provided between the first gap in the circumferential direction and the imaginary line γ1 to satisfy the relationship α < β and the opening angle β is close to the opening angle γ, and the second gap extends to connect with the imaginary line γ2.

2. The permanent magnet motor according to claim 1, characterized in that, As the structure when viewed from a cross-section perpendicular to the rotation axis of the rotor, the outer peripheral hole has an elongated shape along the radial direction of the rotor, and the elongated portion is grounded with the imaginary line γ1 and extends along the second magnetic circuit.

3. The permanent magnet motor according to claim 1 or 2, characterized in that, When the magnetic circuit of one of the teeth is substantially merged with the second magnetic circuit of one of the second magnetic circuits on both sides of each of the second permanent magnets, the magnetic circuit of the other tooth is substantially merged with the second magnetic circuit of the other of the second magnetic circuits on both sides.

Images