Motor

Abstract

A motor (10) includes an annular stator (12) having: a plurality of teeth (16) extending toward an axial center (L) and arranged side by side in a circumferential direction; and a winding (18) wound around the teeth. The motor (10) also includes: a rotor (13) having a rotor core (22) that is rotatably accommodated inside the stator; and a plurality of permanent magnets (23) that are provided inside the rotor core and are arranged side by side in the circumferential direction. A plurality of magnetic pole parts (22b) arranged in the circumferential direction are formed by the plurality of permanent magnets on the surface of the rotor core facing the stator. Each of the magnetic pole parts includes a groove (22c) recessed radially inward. The groove is formed symmetrically in the circumferential direction from the center of the magnetic pole, which is the center in the circumferential direction of the magnetic pole part. The motor is configured such that 0.12 < Wg / (360 / P) < 0.31 is satisfied, where Wg is the angle of the groove width at a radially outer end part of the groove, and P is the number of magnetic pole parts.

Description

Motor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-124595, filed on July 31, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a motor.

[0003] Motors used in devices that require a position-maintaining function, such as electric variable valve timing devices, require a large detent torque. As a motor that aims to improve the detent torque, a motor with grooves on the surface of the rotor that faces the stator has been proposed (see, for example, Patent Document 1).

[0004] JP 2019-41530 A

[0005] In the motor described above, the grooves provided in the rotor can improve the detent torque, but the inventors have been studying a configuration that can also accommodate situations where a larger detent torque is required.

[0006] An object of the present disclosure is to provide a motor capable of ensuring a large detent torque. In a first aspect of the present disclosure, the motor includes: an annular stator having a plurality of teeth extending toward an axial center and arranged side by side in a circumferential direction and windings wound around the teeth; a rotor core rotatably accommodated inside the stator; and a rotor having a plurality of permanent magnets provided inside the rotor core and arranged side by side in a circumferential direction, the permanent magnets forming a plurality of magnetic pole portions arranged in a circumferential direction on a surface of the rotor core facing the stator, wherein the magnetic pole portions have grooves recessed radially inward, the grooves being formed circumferentially symmetrically about a magnetic pole center that is the circumferential center of the magnetic pole portions, and the motor is configured so that 0.12<Wg / (360 / P)<0.31 is satisfied, where Wg is a groove width angle at a radially outer end of the groove and P is the number of the magnetic pole portions.

[0007] With this configuration, the motor is configured to satisfy 0.12<Wg / (360 / P)<0.31, where Wg is the groove width angle at the radially outer end of the grooves formed symmetrically around the circumferential direction from the magnetic pole center, and P is the number of magnetic pole portions, thereby ensuring a large detent torque. In other words, as shown in Figure 4, because the motor is configured to satisfy 0.12<Wg / (360 / P)<0.31, a larger detent torque can be obtained than when 0.12<Wg / (360 / P)<0.31 is not satisfied.

[0008] In a second aspect of the present disclosure, a motor includes a circular stator having a plurality of teeth extending toward an axial center and arranged side by side in the circumferential direction and windings wound around the teeth, a rotor core rotatably accommodated inside the stator, and a rotor having a plurality of permanent magnets provided inside the rotor core and arranged side by side in the circumferential direction, the plurality of permanent magnets forming a plurality of magnetic pole portions arranged circumferentially on the surface of the rotor core facing the stator, wherein the magnetic pole portions have grooves recessed radially inward or holes with closed radial outer ends, and the motor is configured so that at the cogging peak position, the total torque generated by specific teeth among the plurality of teeth that have the same angle relative to the magnetic pole portions is within the range of 80% to 120% of the cogging torque.

[0009] With this configuration, the motor is set so that the total torque generated by specific teeth that have the same angle relative to the magnetic pole portion at the cogging peak position is within the range of 80% to 120% of the cogging torque, thereby enabling a large detent torque to be obtained.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a partial cross-sectional view of a motor according to one embodiment, Fig. 2 is a partial plan view of a motor according to one embodiment, Fig. 3 is an angle-torque characteristic diagram of the motor according to one embodiment, Fig. 4 is a Wg / (360 / P)-detent torque characteristic diagram of the motor according to one embodiment, Fig. 5 is a Wg / (360 / P)-average torque characteristic diagram of the motor according to one embodiment, Fig. 6 is a Wk / (2×Wr+Wg)-detent torque characteristic diagram of the motor according to one embodiment, and Fig. 7 is a graph of the Wg / (360 / P)-average torque characteristic diagram of the motor according to one embodiment. FIG. 8 is a Z / G-detent torque characteristic diagram of a motor in one embodiment, FIG. 9 is a Wu / (360 / P)-detent torque characteristic diagram of a motor in one embodiment, FIG. 10 is a Wk / (360 / S)-detent torque characteristic diagram of a motor in one embodiment, FIG. 11 is a partial plan view of a motor in another example, FIG. 12 is a Wa-detent torque characteristic diagram of a motor in another example, and FIG. 14 is a Wb-detent torque characteristic diagram of a motor in another example, FIG. 15 is a Wb-average torque characteristic diagram of a motor in another example, FIG. 16 is a partial plan view of a motor in another example, FIG. 17 is a (2×Wr1+Wg) / (2×Wr2+Wg)-average torque characteristic diagram of a motor in another example, FIG. 18 is a (2×Wr1+Wg) / (2×Wr2+Wg)-detent torque characteristic diagram of a motor in another example, and FIG. 19 is a partial plan view of a motor in another example. FIG. 20 is a (2×Wr1+Wg) / (2×Wr2+Wg)-ripple rate characteristic diagram of a motor in another example, FIG. 21 is a partial plan view of a motor in another example, FIG. 22 is a partial plan view of a motor in another example, FIG. 23 is a (Wgs-Wg)-average torque characteristic diagram of a motor in another example, FIG. 24 is a partial plan view of a motor in another example, FIG. 25 is a partial plan view of a motor in another example, and FIG. 26 is a partial plan view of a motor in another example.

[0011] An embodiment of a motor will be described below with reference to the drawings. Note that for the sake of convenience, some of the components may be exaggerated or simplified in the drawings. Furthermore, the dimensional proportions of the various components may differ from those of the actual components.

[0012] 1, the motor 10 of this embodiment is an embedded magnet brushless motor. The motor 10 includes an annular stator 12 fixed to the inner peripheral surface of a motor housing 11, and a rotor 13 rotatably housed inside the stator 12.

[0013] (Configuration of Stator 12) The stator 12 has a cylindrical stator core 14, the outer peripheral surface of which is fixed to the motor housing 11. The stator core 14 has an annular portion 15 and a plurality of teeth 16 that extend radially inward from the annular portion 15 toward the axial center L and are arranged side by side in the circumferential direction. In this embodiment, the outer diameter of the stator core 14 is set to 55 mm.

[0014] The teeth 16 are arranged at equal angular intervals. The stator core 14 of this embodiment has 12 teeth 16. That is, the number of slots in the stator 12, which is the same as the number of teeth 16 of this embodiment, is "12." The stator core 14 of this embodiment is made up of a plurality of split cores 17 in which the annular portion 15 is divided for each tooth 16. Although an insulator is to be assembled to each of the split cores 17 of the stator core 14, for example, the insulators are not shown in the drawings, and the stator core 14 is shown schematically.

[0015] The teeth 16 also have umbrella portions 16a that protrude in both circumferential directions at their radially inner ends. The radially inner end faces of the teeth 16, in other words, the radially inner end faces of the umbrella portions 16a, are arc surfaces centered on the axial center L.

[0016] The stator 12 also has three-phase windings 18 wound around the teeth 16. The windings 18 are wound in a concentrated manner around each of the teeth 16 so as to be positioned between the adjacent teeth 16. The stator 12 generates a rotating magnetic field when a three-phase driving current is supplied to the windings 18.

[0017] (Configuration of rotor 13) The rotor 13 has a rotating shaft 21 rotatably provided about an axial center L, a rotor core 22 fixed to the outer periphery of the rotating shaft 21, and a plurality of permanent magnets 23 provided inside the rotor core 22 and arranged side by side in the circumferential direction. The rotating shaft 21 is rotatably supported, for example, by an end housing (not shown) via bearings (not shown).

[0018] The rotor core 22 is formed by stacking a plurality of disk-shaped electromagnetic steel plates in the axial direction. The thickness of the electromagnetic steel plates is set to, for example, 0.25 mm to 0.7 mm, and in this embodiment, electromagnetic steel plates with a thickness of 0.5 mm are used. The outer diameter of the rotor core 22 in this embodiment is set to 30.8 mm.

[0019] The rotor core 22 has a plurality of magnet accommodating portions 22a arranged side by side in the circumferential direction. In this embodiment, the magnet accommodating portions 22a are formed in a U-shape with an opening on the radially outer side. Note that the "U" here refers to a shape in which the radially inner side is curved in a rounded manner when viewed in the axial direction. In this embodiment, the magnet accommodating portions 22a are formed in a shape in which both end portions become increasingly distant from each other as they approach the tips. The plurality of magnet accommodating portions 22a are arranged at equal angular intervals. Furthermore, the rotor core 22 in this embodiment has eight magnet accommodating portions 22a.

[0020] The permanent magnets 23 are accommodated in the magnet accommodating portions 22a. In this embodiment, the permanent magnets 23 are made of samarium-iron bonded magnets and are arranged so as to fill the magnet accommodating portions 22a. That is, the permanent magnets 23 have the same shape as the magnet accommodating portions 22a and are arranged in a U-shape with an open radially outward opening. As a result, a plurality of magnetic pole portions 22b are formed on the surface of the rotor core 22 facing the stator 12 by the plurality of permanent magnets 23 arranged side by side in the circumferential direction. Note that the rotor 13 in this embodiment is an embedded magnet type in which a permanent magnet 23 is arranged in each of the magnetic pole portions 22b, and the number of magnetic pole portions 22b is the same as the number of permanent magnets 23. That is, the number of magnetic poles of the rotor 13, which is the same as the number of magnetic pole portions 22b in this embodiment, is "8."

[0021] (Detailed configuration of grooves 22c, etc.) Here, as shown in FIG. 2 , each magnetic pole portion 22b has a groove 22c recessed radially inward. In other words, the rotor core 22 has each magnetic pole portion 22b with a groove 22c recessed radially inward. The grooves 22c are formed circumferentially symmetrically from the magnetic pole center, which is the circumferential center of each magnetic pole portion 22b. More specifically, the grooves 22c are formed symmetrically about the d-axis on a straight line D that extends radially while passing through the circumferential center of each magnetic pole portion 22b. The grooves 22c are formed throughout the entire axial direction of the rotor core 22. The grooves 22c have a pair of circumferential end faces with a constant width. The radially outer end of each groove 22c is not chamfered with respect to the outer peripheral surface of the rotor core 22, forming a so-called pin angle.

[0022] In the motor 10 of this embodiment, the groove width angle at the radially outer end of the groove 22c is Wg, and the number of magnetic pole portions 22b is P. The groove width angle Wg is set to satisfy 0.12 < Wg / (360 / P) < 0.31. Note that Wg is measured in degrees (°). The angle referred to in this embodiment is the angle about the axial center L, and more specifically, the angle formed by an auxiliary line drawn from the axial center L to a target position. In this embodiment, the groove width angle Wg is set to satisfy 0.12 < Wg / (360 / P) < 0.27. Furthermore, the groove width angle P is set to satisfy 0.15 < Wg / (360 / P) < 0.27. Specifically, in this embodiment, Wg is 7.8°, P is 8, and Wg / (360 / P) = 0.17.

[0023] In the motor 10, the width angle of the teeth 16 at their radially inner ends is defined as Wk, and the width angle of the magnetic path portion 22d of the rotor core 22 that forms a magnetic path on the circumferential side of the groove 22c is defined as Wr, and these are set to satisfy the relationship 0.7 < Wk / (2×Wr+Wg)<1.0. Note that Wk and Wr are expressed in degrees (°). Specifically, in this embodiment, Wk is 19.5°, 2×Wr+Wg is 24.0°, and Wk / (2×Wr+Wg)=0.81.

[0024] Furthermore, the motor 10 is set so that 0.5×Wt<Wr<Wt is satisfied, where Wt is the angle when the minimum width of the teeth 16 is at the same radial position as the magnetic path portion 22d.

[0025] Furthermore, the motor 10 is configured to satisfy Z / G≧0.75, where G is the length of the air gap between the teeth 16 and the rotor core 22 and Z is the radial depth of the grooves 22c. Note that G and Z are expressed in millimeters. Specifically, in this embodiment, G is 0.55 mm, Z is 1.15 mm, and Z / G=2.1.

[0026] Furthermore, the motor 10 is configured so that the angle Wu, which is the sum of the widths of the ends of the circumferentially adjacent permanent magnets 23, satisfies 0.44 < Wu / (360 / P) < 0.58. Note that Wu is expressed in degrees (°). Specifically, in this embodiment, Wu is 21.0°, and Wu / (360 / P) = 0.47.

[0027] Furthermore, the motor 10 is set to satisfy 0.57 < Wk / (360 / S) < 0.78, where Wk is the width angle at the radially inner end of the teeth 16 and S is the number of teeth 16. Specifically, in this embodiment, Wk is 19.5°, S is 12, and Wk / (360 / S) = 0.65.

[0028] Furthermore, in the motor 10 of this embodiment, the total torque generated by specific teeth 16 that are at the same angle relative to the magnetic pole portions 22b among the multiple teeth 16 at the cogging peak position is set to be within the range of 80% to 120% of the cogging torque. This setting is achieved by the configurations and shapes of the stator 12 and rotor 13 described above.

[0029] Specifically, as shown in FIG. 3 , the motor 10 generates torque with characteristic M1 as a whole. Since the motor 10 of this embodiment has 12 slots and 8 magnetic poles, it generates torque with characteristic M1 that pulsates 24 times per rotation of the rotor 13, in other words, a waveform with one cycle of 15°. The teeth 16 are arranged in groups of four teeth 16 spaced 90° apart and oriented at the same angle relative to the magnetic pole portions 22b. The stator 12 has three groups of teeth 16. Each of the three groups of teeth 16 generates torque with characteristics M2, M3, and M4. At angle T1, which corresponds to the cogging peak position, the torque with characteristic M2 generated by a specific group of teeth 16 is set to be within a range H1 of 80% to 120% of the maximum cogging torque of characteristic M1.

[0030] Furthermore, the motor 10 of this embodiment is configured so that the total torque generated by specific teeth 16 at the cogging peak position is equal to the cogging torque. That is, the motor 10 of this embodiment is configured so that the total torque generated by specific teeth 16 and the cogging torque are substantially equal to each other at the cogging peak position. In other words, the motor 10 of this embodiment is configured such that the configurations and shapes of the stator 12 and the rotor 13 are set so that the total torque generated by specific teeth 16 and the cogging torque are equal to each other as much as possible at the cogging peak position. Furthermore, the motor 10 of this embodiment is configured so that the total torque generated by specific teeth 16 that have the same angle with respect to the magnetic pole portions 22b among the multiple teeth 16 is equal to 90% to 110% of the cogging torque at the cogging peak position.

[0031] In addition, the motor 10 of this embodiment is set so that at the cogging peak position, the total torque generated by the teeth 16 other than the specific tooth 16 among the multiple teeth 16 is within the range of -20% (minus 20%) to +20% of the cogging torque.

[0032] Specifically, at the angle T1 where the cogging peak position is located, the total torque of characteristics M3 and M4 generated by two sets of teeth 16 other than one specific set of teeth 16 is set to be within the range H2 of -20% to +20% of the cogging torque.

[0033] Furthermore, the motor 10 of this embodiment is configured so that the torque generated by one of the multiple teeth 16 has a section where the torque remains at zero. Note that the section where the torque remains at zero here is not limited to a section where the torque remains strictly at zero, but is a section where the torque remains substantially at zero, and includes, for example, a section where the torque remains at a small wave that is less than 1 / 10 of the maximum torque. Note that Figure 3 illustrates, for example, section K where the torque remains at zero in characteristic M2. Furthermore, characteristic M2 is the torque generated by four teeth 16, and the torque generated by one tooth 16 is 1 / 4 of characteristic M2 at each angle.

[0034] Next, the operation of this embodiment will be described. When a three-phase drive current is supplied to the windings 18 of the stator 12, a rotating magnetic field is generated in the stator 12. This rotating magnetic field then rotates the rotor 13. When power supply to the windings 18 is stopped, the rotating magnetic field disappears and the rotor 13 stops. At this time, the rotor 13 stops at an angular position where it is magnetically stable relative to the stator 12. In this state, a detent torque acts on the rotor 13.

[0035] Next, the effects of the above embodiment are described below. (1) The magnetic pole portions 22b have grooves 22c recessed radially inward, and the grooves 22c are formed symmetrically in the circumferential direction from the magnetic pole center, which is the circumferential center of the magnetic pole portions 22b. Furthermore, the groove width angle at the radially outer end of the grooves 22c is Wg, and the number of magnetic pole portions 22b is P, and they are set to satisfy 0.12 < Wg / (360 / P) < 0.31. Therefore, a large detent torque can be ensured. Specifically, the provision of the grooves 22c can increase the change in circumferential magnetic flux density in the air gap, thereby ensuring a larger detent torque.

[0036] In other words, as shown in Fig. 4, since the setting satisfies 0.12 < Wg / (360 / P) < 0.31, a larger detent torque can be obtained compared to when 0.12 < Wg / (360 / P) < 0.31 is not satisfied. Note that characteristic A1 in Fig. 4 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Wg / (360 / P) is changed.

[0037] Furthermore, as shown in Fig. 5, the relationship is set so that 0.12 < Wg / (360 / P) < 0.31 is satisfied, so that a large average torque can be obtained. Note that characteristic A2 in Fig. 5 is a waveform obtained by experiment or calculation, and shows the change in average torque when Wg / (360 / P) is changed.

[0038] (2) Since the setting satisfies 0.12<Wg / (360 / P)<0.27, a larger average torque can be obtained while ensuring a large detent torque. In other words, as shown in Fig. 5, since the setting satisfies 0.12<Wg / (360 / P)<0.27, a larger average torque can be obtained compared to when Wg / (360 / P)<0.27 is not satisfied.

[0039] Furthermore, in this embodiment, Wg / (360 / P) is set to 0.17, which is set to satisfy the condition 0.15<Wg / (360 / P)<0.27. By setting Wg / (360 / P)<0.27 in this manner, a larger detent torque can be ensured, as shown in FIG. 4 .

[0040] (3) The width angle of the teeth 16 at the radially inner end portions is defined as Wk, and the width angle of the magnetic path portion 22d of the rotor core 22 that forms a magnetic path on the circumferential side of the groove 22c is defined as Wr, and these are set to satisfy 0.7 < Wk / (2 × Wr + Wg) < 1.0. Therefore, a large detent torque can be ensured.

[0041] In other words, as shown in Fig. 6, since Wk / (2 x Wr + Wg) is set to satisfy 0.7 < Wk / (2 x Wr + Wg) < 1.0, a larger detent torque can be obtained compared to when 0.7 < Wk / (2 x Wr + Wg) < 1.0 is not satisfied. Note that characteristic A3 in Fig. 6 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Wk / (2 x Wr + Wg) is changed.

[0042] (4) The width angle of the magnetic path portion 22d of the rotor core 22 that forms a magnetic path on the circumferential side of the groove 22c is defined as Wr, and the angle when the minimum width of the teeth 16 is at the same radial position as the magnetic path portion 22d is defined as Wt, and the relationship 0.5 × Wt < Wr < Wt is satisfied. Therefore, a large detent torque can be ensured while suppressing a decrease in average torque due to magnetic saturation of the magnetic path portion 22d.

[0043] (5) The length of the air gap between the teeth 16 and the rotor core 22 is G, and the radial depth of the groove 22c is Z, which are set to satisfy Z / G ≥ 0.75. Therefore, by suppressing the leakage magnetic flux in the groove 22c, the magnetic flux can be concentrated in the magnetic path portion 22d, and the change in magnetic flux density in the circumferential direction of the air gap can be increased, thereby ensuring a large detent torque.

[0044] That is, as shown in FIG. 7 , by setting Z / G ≧ 0.75, a larger detent torque can be obtained compared to when Z / G ≧ 0.75 is not satisfied. Note that characteristic A4 in FIG. 7 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Z / G is changed. Furthermore, by setting Z / G ≧ 1.0, a larger detent torque can be ensured and the variation in detent torque can be suppressed. Furthermore, by setting Z / G ≧ 1.5, an even larger detent torque can be ensured and the variation in detent torque can be further suppressed.

[0045] (6) The permanent magnets 23 arranged in each of the magnetic pole portions 22 b are arranged in a U-shape that is open on the radially outer side, making it easy to secure space for providing the grooves 22 c. In other words, if the permanent magnets are arranged in an I-shape that extends perpendicular to the radial direction, it would be difficult to secure space for providing the grooves 22 c, but in comparison, the grooves 22 c can be easily provided.

[0046] (7) The number of magnetic pole portions 22b is P, and the angle between the ends of the circumferentially adjacent permanent magnets 23 is Wu, and the relationship is set to satisfy 0.44<Wu / (360 / P)<0.58. Therefore, a large average torque can be secured while a large detent torque can be secured.

[0047] That is, as shown in Fig. 8, the relationship is set so that 0.44 < Wu / (360 / P) < 0.58 is satisfied, so that a large detent torque can be obtained. Note that characteristic A5 in Fig. 8 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Wu / (360 / P) is changed.

[0048] Furthermore, as shown in Fig. 9, since the setting satisfies 0.44<Wu / (360 / P)<0.58, a larger average torque can be obtained compared to when 0.44<Wu / (360 / P)<0.58 is not satisfied. Furthermore, characteristic A6 in Fig. 9 is a waveform obtained by experiment or calculation, and shows the change in average torque when Wu / (360 / P) is changed.

[0049] (8) The width angle of the radially inner end of each tooth 16 is Wk, and the number of teeth 16 is S, so that 0.57<Wk / (360 / S)<0.78 is satisfied. Therefore, a large detent torque can be ensured.

[0050] In other words, as shown in Fig. 10, since the setting satisfies 0.57<Wk / (360 / S)<0.78, a larger detent torque can be obtained compared to when 0.57<Wk / (360 / S)<0.78 is not satisfied. Note that characteristic A7 in Fig. 10 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Wk / (360 / S) is changed.

[0051] (9) At the cogging peak position, the total torque generated by specific teeth 16 that have the same angle relative to the magnetic pole portions 22b among the multiple teeth 16 is set to be within a range H1 of 80% to 120% of the cogging torque. In this way, a large detent torque can be obtained. If the total torque generated by the specific teeth 16 is set to match the cogging torque at the cogging peak position, a larger detent torque can be obtained.

[0052] (10) At the cogging peak position, the total torque generated by the teeth 16 other than the specific tooth 16 among the plurality of teeth 16 is set to be within a range H2 of −20% to +20% of the cogging torque. In this way, a large detent torque can be obtained.

[0053] (11) The torque generated by one tooth 16 among the plurality of teeth 16 is set to have a section where it transitions at 0. In this way, a large detent torque can be obtained. Note that the description of the above effects (9) to (11) is a method for calculating the effect of the rotor 13. For example, in a specification where the stator 12 has grooves, it is necessary to calculate the effect of the rotor 13 when the stator 12 does not have grooves.

[0054] (12) The motor 10 is configured to satisfy 0.57<Wk / (360 / S)<0.78, where Wk is the width angle at the radially inner end of each tooth 16 and S is the number of teeth 16. This ensures a large detent torque.

[0055] In other words, as shown in Fig. 10, since the setting satisfies 0.57<Wk / (360 / S)<0.78, a larger detent torque can be obtained compared to when 0.57<Wk / (360 / S)<0.78 is not satisfied. Note that characteristic A7 in Fig. 10 is a waveform obtained by experiment or calculation, and shows the change in detent torque when Wk / (360 / S) is changed.

[0056] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be implemented in combination with each other as long as there is no technical contradiction. In the above embodiment, the groove 22c has a pair of circumferential end faces with a constant width, but this is not limited to this, and the circumferential end faces may be inclined so that the groove width increases radially inward.

[0057] For example, it may be modified as shown in Fig. 11. In this example (see Fig. 11), the circumferential end faces 31a of the grooves 31 are inclined so that the width of the grooves 31 increases radially inward. In this way, a large detent torque can be ensured. Specifically, by inclining the end faces 31a, it becomes possible to better control the flow of magnetic flux in the magnetic path portion 22d, and a larger detent torque can be ensured.

[0058] In other words, as shown in Fig. 12, when the circumferential end faces 31a of the grooves 31 are inclined so that the width of the grooves 31 increases radially inward, a larger detent torque can be obtained compared to other cases. Note that characteristic A8 in Fig. 12 is a waveform obtained by experiment or calculation, and shows the change in detent torque when the angle Wa at which the circumferential end faces 31a of the grooves 31 are inclined relative to the aforementioned line D (i.e., the d-axis) is changed. In Fig. 12, the case where the circumferential end faces 31a of the grooves 31 increase in width radially inward is considered to be a negative side.

[0059] In the above embodiment, the end of the permanent magnet 23 is shaped to extend in a direction away from the circumferential end face of the groove 22c as it moves radially outward, but this is not limited to this, and the permanent magnet 23 may also be shaped to have a thick portion that protrudes in a direction approaching the circumferential end face of the groove 22c.

[0060] For example, it may be modified as shown in Fig. 13. In this example (see Fig. 13), the end of the permanent magnet 32 ​​extends in a direction away from the circumferential end face of the groove 22c as it moves radially outward, and has a thick portion 32a, which protrudes in a direction approaching the circumferential end face of the groove 22c.

[0061] In this way, for example, by suppressing the leakage magnetic flux generated in the rotor core 22 that is positioned radially outward from the radially outer end face of the permanent magnet 32, it is possible to ensure a large torque, and by providing a width for pole switching, it is possible to further increase the change in magnetic flux density in the circumferential direction of the air gap, thereby ensuring a large average torque while also ensuring a large detent torque.

[0062] That is, as shown in Fig. 14, a large detent torque can be ensured by setting the angle Wb at which the circumferential end face of the thick portion 32a is inclined relative to the aforementioned line D (i.e., the d-axis) to 0° or less. Note that characteristic A9 in Fig. 14 is a waveform obtained by experiment or calculation, and shows the change in detent torque when the angle Wb at which the circumferential end face of the thick portion 32a is inclined relative to the line D (i.e., the d-axis) is changed. In Fig. 14, the case where the circumferential end face of the thick portion 32a approaches the line D radially outward is considered to be on the negative side.

[0063] 15, a large average torque can be ensured by setting the angle Wb, at which the circumferential end face of the thick portion 32a is inclined relative to the aforementioned line D (i.e., the d-axis), within a range of −20° (minus 20°) to 0°. Note that characteristic A10 in FIG. 15 is a waveform obtained by experiment or calculation, and shows the change in average torque when the angle Wb, at which the circumferential end face of the thick portion 32a is inclined relative to the line D (i.e., the d-axis), is changed. In FIG. 15, the case where the circumferential end face of the thick portion 32a approaches the line D radially outward is considered to be on the negative side.

[0064] In the above embodiment, the rotor 13 is an embedded magnet type in which a permanent magnet 23 is arranged in each of the magnetic pole portions 22b, but this is not limited to this, and the rotor may also be a consequent type in which a permanent magnet is arranged in every other magnetic pole portion in the circumferential direction.

[0065] For example, the rotor 13 may be modified as shown in Fig. 16. The rotor 13 in this example (see Fig. 16) is a consequent type rotor in which permanent magnets 33 are arranged at every other magnetic pole portion 22b in the circumferential direction. The magnetic pole portions 22b include magnetic pole portions 34 in which permanent magnets 33 are arranged and non-magnetic pole portions 35 in which no permanent magnets 33 are arranged, and the magnetic pole portions 34 and non-magnetic pole portions 35 are arranged alternately in the circumferential direction.

[0066] In this example, the magnet accommodating portion 22e in the rotor core 22 is formed in an I-shape extending in a direction perpendicular to the radial direction. The permanent magnets 33 accommodated in the magnet accommodating portion 22e are arranged in the I-shape extending in a direction perpendicular to the radial direction.

[0067] The part of the rotor core 22 that forms a magnetic path on the circumferential side of the groove 22c in the magnetic pole portion 34 forms a magnetic magnetic path portion 22f, and the part of the rotor core 22 that forms a magnetic path on the circumferential side of the groove 22c in the non-magnetic pole portion 35 forms a non-magnetic magnetic path portion 22g.

[0068] The rotor core 22 in this example also has a flux barrier 22h, which is a gap for blocking magnetic flux. The flux barrier 22h in this example is formed so as to communicate with both ends of the magnet accommodating portion 22e.

[0069] The flux barrier 22h is set to satisfy (2×Wr1+Wg) / (2×Wr2+Wg)≦1.5, where Wr1 is the width angle of the magnetic path portion 22f and Wr2 is the width angle of the non-magnetic path portion 22g. Specifically, in this example (see FIG. 16 ), 2×Wr1+Wg is 21.8°, 2×Wr2+Wg is 22.5°, and (2×Wr1+Wg) / (2×Wr2+Wg)=0.97. This ensures a large average torque and a large detent torque. The ripple factor can also be kept small.

[0070] That is, as shown in Fig. 17, the ratio is set so as to satisfy (2 × Wr1 + Wg) / (2 × Wr2 + Wg) ≦ 1.5, so that a large average torque can be obtained. Note that characteristic A11 in Fig. 17 is a waveform obtained by experiment or calculation, and shows the change in average torque when (2 × Wr1 + Wg) / (2 × Wr2 + Wg) is changed.

[0071] Furthermore, as shown in Fig. 18, since the ratio is set so as to satisfy (2 × Wr1 + Wg) / (2 × Wr2 + Wg) ≦ 1.5, a large detent torque can be obtained. Note that characteristics A12 and A13 in Fig. 18 are waveforms obtained by experiment or calculation, and show the change in detent torque when (2 × Wr1 + Wg) / (2 × Wr2 + Wg) is changed.

[0072] Furthermore, because the configuration of this example has the magnetic pole portions 34 and the non-magnetic pole portions 35, two detent torque characteristics A12 and A13 are obtained depending on the angle of the rotor 13. Specifically, as shown in FIG. 19 , the torque characteristics Y1 and Y2 of the motor 10 having the magnetic pole portions 34 and the non-magnetic pole portions 35 have different peak values ​​depending on the angles θ1 and θ2 of the rotor 13. Note that the torque characteristic Y1 is the characteristic when (2×Wr1+Wg) / (2×Wr2+Wg)=0.97 in this example (see FIG. 16 ). The torque characteristic Y2 is the characteristic when (2×Wr1+Wg) / (2×Wr2+Wg)=1.5. When the angle of the rotor 13 is θ1, the change in detent torque when (2×Wr1+Wg) / (2×Wr2+Wg) is changed is characteristic A12. Furthermore, when the rotor angle θ2 is changed, the change in detent torque when (2×Wr1+Wg) / (2×Wr2+Wg) is changed is shown as characteristic A13. Therefore, it is preferable to configure the motor 10 so that, for example, (2×Wr1+Wg) / (2×Wr2+Wg)≦1.22 is satisfied. This reduces the difference in magnetic flux flow between the magnetic pole portions 34 and the non-magnetic pole portions 35, even in the consequent type, and large detent torques with small differences can be obtained for both characteristics A12 and A13. As a result, for example, the rotor 13 can be stably positioned and held at a small angle (360° / 24 in this example). In other words, the motor 10 can have high resolution. It is preferable that (2×Wr1+Wg) / (2×Wr2+Wg) be closer to 1 than 1.22.

[0073] Furthermore, as shown in Fig. 20, the motor 10 is set so as to satisfy the relationship (2 x Wr1 + Wg) / (2 x Wr2 + Wg) ≤ 1.5, thereby keeping the ripple rate small. Note that characteristic A14 in Fig. 20 is a waveform obtained by experiment or calculation, and shows the change in the ripple rate when (2 x Wr1 + Wg) / (2 x Wr2 + Wg) is changed.

[0074] In this example (see FIG. 16), for Wr in the above-mentioned range of 0.7<Wk / (2×Wr+Wg)<1.0, Wr1 is adopted and Wk / (2×Wr+Wg) is set to 0.89. In this example (see FIG. 16), for Wr in the above-mentioned range of 0.5×Wt<Wr<Wt, the larger Wr2 is adopted.

[0075] 21. The rotor 13 in this example (see FIG. 21) is a consequent type in which permanent magnets 36 are arranged at every other magnetic pole portion 22b in the circumferential direction. The magnetic pole portions 22b include magnetic pole portions 34 in which permanent magnets 36 are arranged and non-magnetic pole portions 35 in which no permanent magnets 36 are arranged, and the magnetic pole portions 34 and non-magnetic pole portions 35 are arranged alternately in the circumferential direction.

[0076] The magnet accommodating portion 22j in the rotor core 22 of this example is formed in a U-shape that is open on the radially outer side, and the permanent magnets 36 accommodated in the magnet accommodating portion 22j are arranged in the U-shape that is open on the radially outer side.

[0077] The rotor core 22 in this example also has a flux barrier 22k, which is a gap for blocking magnetic flux. The flux barrier 22k in this example is independent of the magnet accommodating portion 22j and is recessed radially inward from the outer circumferential surface of the rotor core 22.

[0078] The flux barrier 22k is set to satisfy (2×Wr1+Wg) / (2×Wr2+Wg)≦1.5, where Wr1 is the width angle of the magnetic path portion 22f and Wr2 is the width angle of the non-magnetic path portion 22g. Specifically, in this example (see FIG. 21 ), 2×Wr1+Wg is 22.7°, 2×Wr2+Wg is 21.0°, and (2×Wr1+Wg) / (2×Wr2+Wg)=1.08. This configuration also ensures a large average torque and a large detent torque. Furthermore, the ripple rate can be kept small.

[0079] In the above embodiment, the radially inner end surface of the tooth 16, in other words, the radially inner end surface of the umbrella portion 16a, is a simple arc surface, but this is not limited to this and the tooth may have a groove.

[0080] 22, the teeth 16 have tooth grooves 16b recessed radially outward from the radially inner end of the circumferential center of the teeth 16. This makes it possible to ensure even greater detent torque.

[0081] In this example, the groove width angle at the radially inner end of the tooth groove 16b is designated as Wgs, and is set to satisfy Wgs - Wg < 0. Note that Wgs is measured in degrees (°). Specifically, in this example (see FIG. 22), Wg is 8.2°, Wgs is 4.7°, and Wgs - Wg = -3.5°. This ensures a large average torque.

[0082] That is, as shown in Fig. 23, a large average torque can be obtained because Wgs - Wg < 0 is satisfied. Note that characteristic A15 in Fig. 23 is a waveform obtained by experiment or calculation, and shows the change in average torque when Wgs - Wg is changed.

[0083] 24, the tooth grooves 16b may be inclined so that the width of the circumferential end faces 16c becomes narrower as they extend radially outward, thereby ensuring a larger average torque.

[0084] In the above embodiment, the grooves 22c are provided in the same number as the magnetic pole portions 22b, and are provided in each of all the magnetic pole portions 22b, but this is not limited to this and may be changed to another configuration.

[0085] For example, as shown in Fig. 25, the grooves 22c may be provided in half the number of magnetic pole portions 22b, and may be provided on every other magnetic pole portion 22b arranged in the circumferential direction. Specifically, for example, the grooves 22c may be provided on all magnetic pole portions 22b constituting the N poles, but not on the magnetic pole portions 22b constituting the S poles.

[0086] In the above embodiment, the magnet housing portion 22a is formed in a U-shape and the permanent magnet 23 is arranged in a U-shape, but this is not limited thereto. The magnet housing portion 22a may be formed in a V-shape and the permanent magnet may be arranged in a V-shape. The V-shape here refers to a shape that is not curved radially inward when viewed in the axial direction. In this case, for example, the permanent magnet may be arranged in a V-shape by combining two rectangular parallelepiped-shaped magnets. In addition, in the above embodiment, the permanent magnet 23 is made of a samarium-iron bonded magnet, but this is not limited thereto. For example, a rare earth sintered magnet such as a neodymium magnet may be used.

[0087] 26, the magnet accommodating portion 22m may be formed in an I-shape extending in a direction perpendicular to the radial direction, and the permanent magnets 37 accommodated in the magnet accommodating portion 22m may be arranged in an I-shape extending in a direction perpendicular to the radial direction. This example is an embedded magnet type in which the number of magnetic pole portions 22b is the same as the number of permanent magnets 37. The rotor core 22 in this example also has flux barriers 22n, which are gaps for blocking magnetic flux. The flux barriers 22n are formed in communication with both ends of the magnet accommodating portion 22m. The flux barriers 22n extend radially outward from both ends of the magnet accommodating portion 22m, thereby providing space for providing grooves 22c radially outward from the permanent magnets 37.

[0088] In the above embodiment, the grooves 22c are configured to open radially outward of the rotor core 22. However, this is not limited to this, and the grooves 22c may be changed to, for example, holes that are recessed radially inward and have closed radially outer ends. In other words, the grooves 22c may be changed to holes that have other configurations that block magnetic flux in a substantially similar manner.

[0089] In the above embodiment, the stator core 14 is made up of a plurality of split cores 17 in which the annular portion 15 is divided for each tooth 16, but this is not limited to this, and the stator core may also have an annular portion 15 that is not divided.

[0090] In the above embodiment, the rotor has twelve teeth 16 and eight magnetic pole portions 22 b, but the number of teeth 16 and the number of magnetic pole portions 22 b may be changed. In other words, the number of slots and the number of magnetic poles may be changed.

[0091] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0092] The features of the present invention are as follows: [1] A rotor having an annular stator (12) having a plurality of teeth (16) extending toward an axial center (L) and arranged side by side in the circumferential direction and windings (18) wound around the teeth, a rotor core (22) rotatably accommodated inside the stator, and a plurality of permanent magnets (23, 32, 33, 36, 37) provided inside the rotor core and arranged side by side in the circumferential direction, and a rotor having a surface of the rotor core facing the stator, the surface of the rotor core facing the stator being formed by the plurality of permanent magnets. A motor (10) including a rotor (13) on which a plurality of magnetic pole portions (22b) arranged in a circumferential direction are formed, the magnetic pole portions having grooves (22c, 31) recessed radially inward, the grooves being formed symmetrically in the circumferential direction from a magnetic pole center which is the circumferential center of the magnetic pole portions, and the motor is configured so that 0.12<Wg / (360 / P)<0.31 is satisfied, where Wg is the angle of the groove width at the radially outer end of the groove and P is the number of the magnetic pole portions.

[0093] [2] The motor according to the above [1], wherein the motor is configured to satisfy 0.12<Wg / (360 / P)<0.27. [3] The motor according to the above [1] or [2], wherein the motor is configured to satisfy 0.7<Wk / (2×Wr+Wg)<1.0, where Wk is the width angle at the radially inner end of the tooth and Wr is the width angle of the magnetic path portion (22d) of the rotor core that forms a magnetic path on the circumferential side of the groove.

[0094] [4] A motor described in any one of [1] to [3] above, wherein the angle of the width of the magnetic path portion of the rotor core that forms a magnetic path on the circumferential side of the groove is Wr, and the angle when the minimum width of the tooth is at the same radial position as the magnetic path portion is Wt, and the motor is configured so that 0.5 x Wt < Wr < Wt is satisfied.

[0095] [5] A motor described in any one of [1] to [4] above, wherein the motor is configured so that Z / G≧0.75 is satisfied, where G is the length of the air gap between the teeth and the rotor core and Z is the radial depth of the groove.

[0096] [6] The motor according to any one of [1] to [5] above, wherein the permanent magnets arranged in each of the magnetic pole portions are arranged in a U-shape or a V-shape that is open radially outward. [7] The motor according to [6] above, wherein the number of the magnetic pole portions is P, and the angle between the ends of the permanent magnets adjacent in the circumferential direction is Wu, and the motor is configured so that 0.44 < Wu / (360 / P) < 0.58 is satisfied.

[0097] [8] A motor described in any one of [1] to [7] above, wherein the circumferential end surface (31a) of the groove (31) is inclined so that the width of the groove becomes wider as it moves radially inward.

[0098] [9] A motor described in any one of [1] to [8] above, wherein the end of the permanent magnet (32) extends in a direction away from the circumferential end face of the groove as it moves radially outward and has a thick portion (32a), and the thick portion protrudes in a direction approaching the circumferential end face of the groove.

[0099]

[10] The motor described in any one of [1] to [5], [8] and [9] above, wherein the permanent magnets (33, 36) are arranged at every other one in the circumferential direction of the plurality of magnetic pole portions, the plurality of magnetic pole portions including magnetic pole portions (34) in which the permanent magnets are arranged and non-magnetic pole portions (35) in which the permanent magnets are not arranged, the magnetic pole portions and the non-magnetic pole portions are arranged alternately in the circumferential direction, and where an angle of a width of a magnetic magnetic path portion (22f) of the rotor core that forms a magnetic path on a circumferential side of the groove in the magnetic magnetic pole portion is Wr1 and an angle of a width of a non-magnetic magnetic path portion (22g) of the rotor core that forms a magnetic path on a circumferential side of the groove in the non-magnetic magnetic pole portion is Wr2, and flux barriers (22h, 22k) are set so as to satisfy (2×Wr1+Wg) / (2×Wr2+Wg)≦1.5.

[0100]

[11] A motor described in any one of [1] to

[10] above, wherein the teeth have tooth grooves (16b) recessed radially outward from the radially inner end of the circumferential center of the teeth.

[0101]

[12] The motor described in

[11] above, wherein the angle of the groove width at the radially inner end of the tooth groove is Wgs, and the motor is configured so that Wgs-Wg<0 is satisfied.

[13] A motor comprising: an annular stator (12) having a plurality of teeth (16) extending toward an axial center (L) and arranged side by side in the circumferential direction, and windings (18) wound around the teeth; a rotor core (22) rotatably accommodated inside the stator; and a rotor (13) having a plurality of permanent magnets (23, 32, 33, 36, 37) provided inside the rotor core and arranged side by side in the circumferential direction, the rotor core having a surface facing the stator where a plurality of magnetic pole portions (22b) are formed by the plurality of permanent magnets and arranged side by side in the circumferential direction, wherein the magnetic pole portions have grooves (22c, 31) recessed radially inward or holes with closed radial outer ends, and the total torque generated by specific teeth among the plurality of teeth that have the same angle with respect to the magnetic pole portions is set to be within a range of 80% to 120% of the cogging torque at the cogging peak position.

[0102]

[14] The motor according to

[13] above, wherein the motor is set so that the total torque generated by the specific teeth at the cogging peak position is equal to the cogging torque.

[0103]

[15] A motor as described in

[13] or

[14] above, wherein the motor is configured so that at the cogging peak position, the total torque generated by teeth other than the specific tooth among the plurality of teeth is within the range of -20% to +20% of the cogging torque.

[0104]

[16] A motor according to any one of

[13] to

[15] above, wherein the motor is configured so that the torque generated by one of the plurality of teeth has a section in which it remains at zero.

Claims

1. A motor (10) comprising: an annular stator (12) having a plurality of teeth (16) extending toward an axial center (L) and arranged side by side in the circumferential direction, and a winding (18) wound around the teeth; a rotor core (22) rotatably accommodated inside the stator; and a rotor (13) having a plurality of permanent magnets (23, 32, 33, 36, 37) provided inside the rotor core and arranged side by side in the circumferential direction, the rotor core having a surface facing the stator on which a plurality of magnetic pole portions (22b) arranged side by side in the circumferential direction are formed by the plurality of permanent magnets, wherein the magnetic pole portions have grooves (22c, 31) recessed radially inward, the grooves being formed symmetrically in the circumferential direction from a magnetic pole center which is the circumferential center of the magnetic pole portions, and the groove width angle at the radially outer end of the groove is Wg, and the number of the magnetic pole portions is P, and the relationship between the groove width and the number of the magnetic pole portions is 0.12<Wg / (360 / P)<0.

31. The motor is configured to satisfy:

2. The motor according to claim 1, wherein the motor is set so as to satisfy 0.12<Wg / (360 / P)<0.

27.

3. The motor according to claim 1, wherein the motor is configured so that 0.7 < Wk / (2 x Wr + Wg) < 1.0 is satisfied, where Wk is the width angle at the radially inner end of the tooth, and Wr is the width angle of the magnetic path portion (22d) of the rotor core which forms a magnetic path on the circumferential side of the groove.

4. The motor according to claim 1, wherein the motor is configured so as to satisfy 0.5 × Wt < Wr < Wt, where Wr is the angle of the width of the magnetic path portion of the rotor core which forms a magnetic path on the circumferential side of the groove, and Wt is the angle when the minimum width of the teeth is at the same radial position as the magnetic path portion.

5. The motor according to claim 1, wherein the motor is configured so as to satisfy Z / G≧0.75, where G is a length of an air gap between the teeth and the rotor core, and Z is a radial depth of the groove.

6. The motor according to claim 1, wherein the permanent magnets arranged in each of the magnetic pole portions are arranged in a U-shape or a V-shape that is open radially outward.

7. The motor according to claim 6, wherein the motor is configured so as to satisfy 0.44<Wu / (360 / P)<0.58, where P is the number of magnetic pole portions and Wu is the angle between the combined widths of the ends of the permanent magnets adjacent in the circumferential direction.

8. The motor according to claim 1, wherein a circumferential end face (31a) of the groove (31) is inclined so that the width of the groove becomes wider toward the radially inner side.

9. The motor according to claim 1, wherein an end of the permanent magnet (32) extends in a direction away from the circumferential end face of the groove as it moves radially outward and has a thick portion (32a), the thick portion protruding in a direction approaching the circumferential end face of the groove.

10. The motor as claimed in claim 1, wherein the permanent magnets (33, 36) are arranged alternately in the circumferential direction of the plurality of magnetic pole portions, the plurality of magnetic pole portions include magnetic pole portions (34) in which the permanent magnets are arranged and non-magnetic pole portions (35) in which the permanent magnets are not arranged, the magnetic pole portions and the non-magnetic magnetic pole portions are arranged alternately in the circumferential direction, and wherein the flux barriers (22h, 22k) are set so as to satisfy the following relationship: (2×Wr1+Wg) / (2×Wr2+Wg)≦1.5, where Wr1 is an angle of a width of the magnetic magnetic path portion (22f) of the rotor core which forms a magnetic path on the circumferential side of the groove in the magnetic magnetic pole portion, and Wr2 is an angle of a width of the non-magnetic magnetic path portion (22g) of the rotor core which forms a magnetic path on the circumferential side of the groove in the non-magnetic magnetic pole portion.

11. The motor according to claim 1, wherein the teeth have tooth grooves (16b) recessed radially outward from the radially inner end of the circumferential center of the teeth.

12. The motor according to claim 11, wherein the groove width angle at the radially inner end of the teeth groove is Wgs, and the motor is configured so as to satisfy Wgs-Wg<0.

13. A motor comprising: an annular stator (12) having a plurality of teeth (16) extending toward an axial center (L) and arranged side by side in the circumferential direction, and windings (18) wound around the teeth; a rotor core (22) rotatably accommodated inside the stator; and a rotor (13) having a plurality of permanent magnets (23, 32, 33, 36, 37) provided inside the rotor core and arranged side by side in the circumferential direction, the rotor core having a surface facing the stator on which a plurality of magnetic pole portions (22b) arranged side by side in the circumferential direction are formed by the plurality of permanent magnets, wherein the magnetic pole portions have grooves (22c, 31) recessed radially inward, or holes with closed radially outer ends, and the motor is configured such that, at a cogging peak position, a total torque generated by a specific tooth among the plurality of teeth that has the same angle with respect to the magnetic pole portions is within a range of 80% to 120% of the cogging torque.

14. The motor according to claim 13, wherein the motor is set so that the total torque generated by the specific teeth at the cogging peak position coincides with the cogging torque.

15. The motor according to claim 13, wherein the motor is set so that, at the cogging peak position, the total torque generated by teeth other than the specific tooth among the plurality of teeth is within a range of -20% to +20% of the cogging torque.

16. The motor according to claim 13, wherein the motor is configured so that the torque generated by one of the plurality of teeth has a section during which the torque remains at zero.

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