Motor and motor unit

Abstract

To provide a motor with high salient poles. [Solution] The motor 100 comprises a rotor 10 having a first magnet 11, a second magnet 12, and a magnetic body 13 located between the first magnet 11 and the second magnet 12 in the direction of the rotation axis, and a stator 20 having a plurality of coils 22, wherein the magnetic body 13 comprises a ring 131 and a plurality of protrusions 132 protruding from the ring 131 toward the stator 20, and the plurality of protrusions 132 are obtained by being located on the q axis of the first magnet 11 and the second magnet 12.

Description

[Technical Field]

[0001] The present invention relates to a motor and a motor unit. [Background technology]

[0002] Conventionally, methods have been proposed that utilize the saliency of the rotor to estimate the initial position of a synchronous motor. For example, Patent Document 1 discloses a surface magnet synchronous motor that has a salient pole that protrudes toward the peripheral surface of the stator at the position of the d-axis, which is the center direction of the magnetic pole of the rotor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-065803 Summary of the Invention [Problem to be solved by the invention]

[0004] When the rotor saliency is small, the detected signal-to-noise ratio is low, which tends to reduce the accuracy of estimating the initial position when the motor is started. For this reason, a high saliency ratio is sometimes desirable to drive the motor stably.

[0005] An example of an object of the present invention is to provide a motor with high salient poles. [Means for solving the problem]

[0006] A motor in one aspect of the present invention comprises a rotor having a first magnet, a second magnet, and a magnetic body located between the first magnet and the second magnet in the direction of the rotation axis, and a stator having a plurality of coils, wherein the magnetic body comprises a ring and a plurality of protrusions protruding from the ring toward the stator, and the plurality of protrusions are on the q axis of the first magnet and the second magnet. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a motor according to an embodiment. [Figure 2] 2 is a cross-sectional view of the motor shown in FIG. 1 taken along the line AA. [Figure 3] FIG. 2 is a schematic plan view for explaining the structure of the rotor and the stator shown in FIG. [Figure 4] FIG. 4 is a perspective view of the rotor and the stator shown in FIG. 3. [Figure 5] 3 is a cross-sectional view of the motor shown in FIG. 2, in which a rotor and a stator are partially cut away. [Figure 6] 10 is a graph showing the relationship between the circumferential size of the protrusion of the magnetic body of the rotor and the salient pole ratio. [Figure 7] 10 is a graph showing the relationship between the radial size of the protrusions of the magnetic body of the rotor and the salient pole ratio. [Figure 8] 2 is a diagram illustrating a configuration of a motor unit according to an embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] First, a summary of a representative embodiment of the invention disclosed in this application will be described. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of elements may differ from the actual situation. The drawings may also include portions where the dimensional relationships and ratios differ from one another.

[0009] [Motor configuration] FIG. 1 is a plan view of a motor according to an embodiment. FIG. 2 is a cross-sectional view of the motor shown in FIG. 1 taken along the line AA. FIG. 3 is a schematic plan view for explaining the structure of the rotor and the stator shown in FIG. FIG. 4 is a perspective view of the rotor and the stator shown in FIG. FIG. 5 is a cross-sectional view of the motor shown in FIG. 2, in which a portion of the rotor and the stator are cut away and displayed.

[0010] 1 and 2 is, for example, a surface magnet motor. Motor 100 includes rotor 10, stator 20, rotating shaft 30 (hereinafter also referred to as "shaft 30"), first bearing 41, second bearing 42, and casing 50. Casing 50 accommodates rotor 10, stator 20, part of shaft 30, first bearing 41, second bearing 42, etc. For convenience of explanation, the first bearing 41, the second bearing 42, and the casing 50 are omitted from FIG.

[0011] In this embodiment, for convenience of explanation, the motor 100 is disposed so that the shaft 30 extends in the direction of the Z axis in a three-dimensional space formed by the X-axis, Y-axis, and Z-axis. In the following explanation, the direction in which the shaft 30 extends (longitudinal direction) is referred to as the "rotational axis direction." The direction in which the rotor 10 rotates around the rotational axis is referred to as the "rotational direction" or "circumferential direction." The direction perpendicular to the rotational axis direction is referred to as the "radial direction." In the radial direction, the side closer to the shaft 30 is referred to as the "inner" or "inside," and the side farther from the shaft 30 is referred to as the "outer" or "outside."

[0012] 1 to 5, rotor 10 includes a first magnet 11 on one side in the direction of the rotation axis, a second magnet 12 on the other side in the direction of the rotation axis, a magnetic body 13 between first magnet 11 and second magnet 12 in the direction of the rotation axis, a plurality of spaces 14 surrounded by first magnet 11, second magnet 12, and magnetic body 13, and non-magnetic body 15. As will be described later, part or all of one or more spaces 14 may be occupied by a non-magnetic body.

[0013] The rotor 10 is located inside the stator 20 in the radial direction. The rotor 10 is also arranged facing the stator 20 in the radial direction. In this embodiment, the motor 100 is an inner rotor type motor. The rotor 10 has an annular (ring) or approximately annular shape. A non-magnetic body 15 is arranged in the inner portion (interior) of the rotor 10 in the radial direction.

[0014] The non-magnetic body 15 has a recess 151 recessed radially from the outer peripheral surface 15O of ​​the non-magnetic body 15 toward the inside (toward the shaft 30). In the rotation axis direction, the non-magnetic body 15 has an upper end 15U (one end side of the shaft 30), a lower end 15D (one end side of the shaft 30), and an intermediate portion 15M between the upper end 15U and the lower end 15D. The recess 151 is formed in the intermediate portion 15M. In this embodiment, the recess 151 is located near the center of the intermediate portion 15M in the rotation axis direction. In particular, the non-magnetic body 15 has a central portion 15C, and the recess 151 is formed in this central portion 15C. A ring 131 serving as the magnetic body 13, which will be described later, is disposed in the recess 151.

[0015] A hole 16 is provided radially inside the rotor 10 (at the center of the rotor 10 in this embodiment) that penetrates the rotor 10 in the direction of the rotation axis. The hole 16 is surrounded by an inner circumferential portion 10I of the rotor 10. A shaft 30 is fitted into the hole 16. The shaft 30 fitted into the hole 16 is surrounded by an inner circumferential portion 15I of the non-magnetic body 15. A first magnet 11 and a second magnet 12 are arranged radially outside the non-magnetic body 15.

[0016] The first magnet 11 and the second magnet 12 have an annular (ring) or approximately annular shape and are so-called permanent magnets containing magnetic powder. The first magnet 11 and the second magnet 12 may be formed, for example, as follows. That is, first, two magnets (two magnetic bodies having magnetic powder) having an annular (ring) or approximately annular shape are arranged with a predetermined gap in the rotation axis direction. The two magnets are also arranged so as to surround the outer peripheral surface of the non-magnetic body 15 in the radial direction. Then, the two magnets may be magnetized so that the north and south poles alternate in the circumferential direction (post-magnetization). Alternatively, two magnets that have been magnetized (pre-magnetization) may be arranged with a predetermined gap in the rotation axis direction. Of the magnets formed in this way, the magnet on one side in the rotation axis direction is the first magnet 11, and the magnet on the other side in the rotation axis direction is the second magnet 12. The above gap corresponds to the thickness T3 of the magnetic body 13 in the rotation axis direction.

[0017] The first magnet 11 and the second magnet 12 have different polarities every 45 degrees in the circumferential direction. That is, the first magnet 11 and the second magnet 12 each have eight poles. Furthermore, the two different magnetic poles (North and South poles) of the first magnet 11 and the second magnet 12 form a d-axis, which is the direction of magnetic flux. In this embodiment, multiple d-axes are formed, and FIG. 3 shows d1-axis, d2-axis, and d3-axis. These d1-axis, d2-axis, and d3-axis are formed on the first magnet 11 and the second magnet 12 at phase intervals of 90 degrees in electrical angle.

[0018] For example, in the d1 axis direction in Figure 3, the first magnet 11 and the second magnet 12 have a polarity of south pole, in the d2 axis direction, the first magnet 11 and the second magnet 12 have a polarity of north pole, and in the d3 axis direction, the first magnet 11 and the second magnet 12 have a polarity of south pole. However, the angle at which the polarity changes in the circumferential direction is not limited to 45 degrees, and may be set to any angle such as 30 degrees or 60 degrees depending on the number and positions of the salient poles.

[0019] As described above, the first magnet 11 is disposed on one side in the direction of the rotation axis, i.e., on the side (upper side) of the second bearing 42 described later. As described above, the second magnet 12 is disposed on the other side in the direction of the rotation axis, i.e., on the side (lower side) of the first bearing 41 described later. The first magnet 11 and the second magnet 12 are formed so that the positions of the polarities in the direction of the rotation axis are the same.

[0020] The magnetic body (yoke) 13 includes a ring 131 having an annular (annular) or approximately annular shape, and a plurality of protrusions 132 protruding radially outward (toward the stator 20) from the ring 131. The magnetic body 13 is formed of, for example, a soft magnetic body, and may be formed of a steel plate such as a silicon steel plate or an electromagnetic soft iron plate, soft ferrite, or the like. The magnetic body 13 may be formed of a single thin plate, or may be formed of a plurality of thin plates. In this embodiment, the magnetic body 13 is formed of a single thin plate.

[0021] The magnetic body 13 is fitted into the recess 151 of the non-magnetic body 15. Specifically, the ring 131 of the magnetic body 13 is fitted into the recess 151 of the non-magnetic body 15, and the protrusion 132 protrudes from the recess 151. In this embodiment, the thickness T3 of the magnetic body 13 in the rotational axis direction is smaller than the thickness T1 of the first magnet 11 in the rotational axis direction or the thickness T2 of the second magnet 12 in the rotational axis direction. The magnetic flux of the first magnet 11 and the second magnet 12 passes through the magnetic body 13 having such a thickness T3, and magnetic interaction can be generated between the non-magnetic body 15 of the rotor 10 and the magnetic body 21 of the stator 20.

[0022] As described above, the ring 131 has an annular (ring) or approximately annular shape. In the radial direction, the size of the outer periphery of ring 131 is smaller than the size of the outer periphery of first magnet 11 and second magnet 12 and larger than the size of the outer periphery of non-magnetic body 15. In the radial direction, the size of the inner periphery of the ring 131 is smaller than the size of the outer periphery of the non-magnetic body 15 .

[0023] The plurality of protrusions 132 are arranged at predetermined intervals in the circumferential direction. Each of the plurality of protrusions 132 is formed to protrude from the ring 131 radially outward (toward the stator 20). In this embodiment, the multiple protrusions 132 are arranged at 45-degree intervals in the circumferential direction. Specifically, the multiple protrusions 132 are located on multiple q axes (q1 axis and q2 axis in FIG. 3) that are perpendicular to the multiple d axes (d1 axis, d2 axis, and d3 axis in FIG. 3) of the first magnet 11 and the second magnet 12. In other words, the multiple protrusions 132 are arranged between the multiple q axes in the circumferential direction. However, the number of protrusions 132 may be any number that corresponds to the number of poles that first magnet 11 and second magnet 12 have. In this embodiment, the dimensions of the protrusion 132 in the radial direction are the same as or approximately the same as the dimensions of the first magnet 11 and the second magnet 12.

[0024] Each of the multiple spaces 14 is a space surrounded by the first magnet 11, the second magnet 12, and the magnetic body 13, and is an area that is open radially toward the stator 20. Specifically, each of the multiple spaces 14 is sandwiched in the rotational axis direction between the first magnet 11 that forms the upper surface and the second magnet 12 that forms the lower surface, and is surrounded in the radial direction by a ring 131 that forms the inner wall. Furthermore, each of the multiple spaces 14 is located between multiple protrusions 132 in the circumferential direction.

[0025] 3 shows three spaces 14A, 14B, and 14C among the multiple spaces 14. Space 14A is formed on the d1 axis, space 14B is formed on the d2 axis, and space 14C is formed on the d3 axis. Since multiple spaces 14 are located between multiple protrusions 132 in the circumferential direction, the magnetic permeability in the multiple spaces 14 is low, and the magnetic flux of the first magnet 11 and the second magnet 12 passes through the magnetic body 13, which has a higher magnetic permeability than the magnetic permeability in the multiple spaces 14. In other words, the magnetic body 13 forms a magnetic path through which the magnetic flux of the first magnet 11 and the second magnet 12 passes. Note that a non-magnetic body having a magnetic permeability lower than that of the magnetic body 13 may be provided in the space 14.

[0026] The space 14 or the non-magnetic material disposed within the space 14 functions as a so-called flux barrier. Hereinafter, the space 14 and the non-magnetic material disposed within the space 14 may be collectively referred to as the "flux barrier 14."

[0027] The non-magnetic body 15 is formed from a non-magnetic metallic material such as aluminum, and has a disk-like (annular) or approximately disk-like shape. An inner peripheral portion 15I that forms a hole in the radial direction is provided at the center of the non-magnetic body 15. The shaft 30 is fitted into the inner peripheral portion 15I of the non-magnetic body 15.

[0028] The stator 20 has an annular (ring-shaped) or approximately annular shape. The stator 20 surrounds the first magnet 11 and the second magnet 12 in the radial direction. The first magnet 11 and the second magnet 12 are disposed inside the stator 20. The stator 20 includes a magnetic body (stator core) 21, an insulator 23, and a plurality of coils 22 wound around the insulator 23.

[0029] The magnetic body 21 is formed, for example, by stacking multiple thin, cylindrical steel plates in the rotational axis direction. The magnetic body 21 has the same axis as the rotor 10. The magnetic body 21 includes a yoke 211, which is an annular portion, multiple spokes 214 extending radially inward (toward the rotor 10) from the yoke 211, and multiple magnetic pole portions (salient pole portions) 213. The multiple magnetic pole portions 213 include end portions 213E extending on both sides from the multiple spokes 214 in the circumferential direction. The multiple magnetic pole portions 213 and the multiple spokes 214 form so-called multiple teeth. Multiple slots 212 are formed between the multiple spokes 214 in the circumferential direction. Multiple coils 22 arranged in the multiple slots 212 are wound around the multiple spokes 214 with multiple insulators 23 interposed therebetween. The yoke 211 has an annular (annular) or approximately annular shape and includes an inner peripheral portion 211I and an outer peripheral portion 211O.

[0030] In this embodiment, a total of 12 spokes 214 and 12 magnetic pole portions 213 are provided at 30-degree intervals in the circumferential direction, but this is not limited thereto, and any number of spokes 214 and magnetic pole portions 213 may be provided at a predetermined interval or angle in the circumferential direction. Note that the number of spokes 214 and the number of magnetic pole portions 213 may be changed as appropriate depending on the number of poles of the first magnet 11 and the second magnet 12.

[0031] The coil 22 is made of a conductive material such as copper or aluminum. In this embodiment, one coil 22 is provided for each spoke 214, for a total of 12 coils 22, but this is not limited to this and any number of coils may be provided corresponding to the number of poles of the first magnet 11 and the second magnet 12.

[0032] The shaft 30 is made of, for example, a metal material and has a cylindrical (pillar) or approximately cylindrical shape. The shaft 30 is fixed to the inner periphery 15I of the non-magnetic body 15. The first magnet 11, the second magnet 12, the magnetic body 13, the flux barrier 14, and the non-magnetic body 15 of the rotor 10 rotate integrally with the shaft 30.

[0033] The first bearing 41 and the second bearing 42 rotatably support the shaft 30 relative to the casing 50. The shaft 30 has one end 31 and the other end 32. In the direction of the rotation axis, the first bearing 41 is arranged on the other end 32 side of the shaft 30, and the second bearing 42 is arranged on the one end 31 side of the shaft 30, relative to the rotor 10 and the stator 20. In other words, the rotor 10 and the stator 20 are arranged between the first bearing 41 and the second bearing 42 in the direction of the rotation axis. The first bearing 41 and the second bearing 42 rotatably support the shaft 30 relative to the casing 50.

[0034] In this embodiment, the first bearing 41 is, for example, a ball bearing including an inner ring, an outer ring, and rolling elements (balls). The inner peripheral surface of the inner ring of the first bearing 41 is attached to the outer peripheral surface of the portion of the shaft 30 on the other end 32 side. In addition, the outer peripheral surface of the outer ring of the first bearing 41 is attached to the inner surface of the protruding portion 541 on the lower side of the casing 50.

[0035] In this embodiment, the second bearing 42 is, for example, a ball bearing including an inner ring, an outer ring, and rolling elements (balls). The inner peripheral surface of the inner ring of the second bearing 42 is attached to the outer peripheral surface of a portion of the shaft 30 on the side of one end 31. In addition, the outer peripheral surface of the outer ring of the second bearing 42 is attached to the inner surface of the upper protrusion 542 of the casing 50. Furthermore, as the first bearing 41 and the second bearing 42, a sliding bearing, an oil-impregnated sintered bearing, a gas bearing, or a magnetic bearing may be used.

[0036] The casing 50 is formed, for example, from a metal material and has a cylindrical shape (outer shape). The casing 50 includes a housing having an upper surface 52 (cover), a lower surface 51 (bottom), and a cylindrical portion 53. The rotor 10 and the stator 20 are housed in the space inside the casing 50. The bottom of the casing 50 has an inner periphery that forms a hole, and a first bearing 41 is attached to the inner periphery of the bottom. The lid of the casing 50 has an inner periphery that forms a hole, and a second bearing 42 is attached to the inner periphery of the lid.

[0037] [Relationship between circumferential size of convexity and salient pole ratio, and radial size of convexity and salient pole ratio] Next, the relationship between the circumferential size of the protrusion 132 and the salient pole ratio, and the relationship between the radial size of the protrusion 132 and the salient pole ratio will be described.

[0038] FIG. 6 is a graph showing the relationship between the circumferential size of the protrusions of the magnetic material of the rotor and the salient pole ratio.

[0039] In FIG. 6, the vertical axis indicates the magnitude of the salient pole ratio (hereinafter sometimes referred to as "SPR"), which represents the ratio of the synchronous inductance Lq of the rotor 10 in the q-axis direction to the synchronous inductance Ld of the rotor 10 in the d-axis direction. That is, the SPR is a value calculated by the following equation (1) in relation to the synchronous inductance Ld of the rotor 10 in the d-axis direction and the synchronous inductance Lq of the rotor 10 in the q-axis direction.

[0040] SPR=Lq / Ld…(1)

[0041] In FIG. 6, the horizontal axis indicates the percentage of the length (width) of the protrusion 132 in the circumferential direction relative to the distance between the two different magnetic poles of the first magnet 11 and the second magnet 12 in the circumferential direction. That is, R1 on the horizontal axis (length (width) of the protrusion in the circumferential direction / distance between two different magnetic poles) is a value calculated using the following equation (2) in relation to the distance D1 (see Figure 3) between the magnetic poles of the first magnet 11 and the second magnet 12 in the circumferential direction and the length (width) D2 (see Figure 3) of the protrusion 132 in the circumferential direction.

[0042] R1 = {(D2) / (D1)} × 100…(2)

[0043] In FIG. 6, when R1 is about 20%, the SPR is about 1.15. Furthermore, when R1 is approximately 38%, the SPR is approximately 1.18, which is the maximum value of the SPR saliency ratio. Furthermore, when R1 is approximately 53%, the SPR is approximately 1.16.

[0044] From the graph of FIG. 6, when R1 is in the range of 0 to approximately 38%, the SPR increases as R1 increases. On the other hand, when R1 is in a range exceeding approximately 38%, the SPR decreases as R1 increases.

[0045] When R1 increases, that is, when the length (width) of the protrusions 132 in the circumferential direction increases, the side portions of the multiple protrusions 132 on the q axis come closer to the d axis. Therefore, when the side of the protrusion 132 approaches the d-axis, it is affected by the magnetic fields generated by the first magnet 11 and the second magnet 12, and as R1 increases, SPR increases until R1 reaches its maximum value. However, once R1 exceeds the maximum value, SPR decreases as R1 increases.

[0046] Therefore, in order to ensure a high salient pole ratio of the rotor 10, it is preferable to set the magnitude of R1 (the length of the convexity in the circumferential direction / the distance between two different magnetic poles) within the range of 20 to 50%.

[0047] FIG. 7 is a graph showing the relationship between the radial size D3 (see FIG. 3) of the protrusion of the magnetic material of the rotor and the salient pole ratio SPR.

[0048] In FIG. 7, the vertical axis indicates the magnitude of the salient pole ratio, which represents the ratio of the synchronous inductance Lq of the rotor 10 in the q-axis direction to the synchronous inductance Ld of the rotor 10 in the d-axis direction. That is, the salient pole ratio is a value calculated by the above formula (1) in relation to the synchronous inductance Ld of the rotor 10 in the d-axis direction and the synchronous inductance Lq of the rotor 10 in the q-axis direction. In FIG. 7, the horizontal axis represents the length D3 of the protrusion 132 in the radial direction (see FIG. 3).

[0049] In FIG. 7, when D3 is about 1 mm, SPR is about 1.1. Furthermore, when D3 is approximately 2 mm, SPR is approximately 1.15. Furthermore, when D3 is about 5 to about 8 mm, SPR is about 1.16.

[0050] From the graph of FIG. 7, when D3 is in the range of 0 to about 2 mm, the SPR increases as the length of the protrusion 132 in the radial direction increases. On the other hand, when D3 is between approximately 2 and approximately 5 mm, the SPR increases as the length of the convex 132 in the radial direction increases, but the change in SPR when D3 is in the range of 2 mm to 5 mm is smaller than the change in SPR when D3 is in the range of 0 to approximately 2 mm. When D3 exceeds approximately 5 mm, even if the length of the protrusion 132 in the radial direction changes, the SPR hardly changes and remains a substantially constant value.

[0051] By making the length of the projection 132 in the radial direction approximately 2 mm or more, a high salient pole ratio of the rotor 10 can be ensured. Furthermore, when the length of the protrusion 132 in the radial direction exceeds the maximum value, the salient pole ratio hardly changes even if the length of the protrusion 132 in the radial direction changes, and remains at a substantially constant value.

[0052] Therefore, by setting the length of the projection 132 in the radial direction within a range of approximately 2 mm to approximately 5 mm, a high salient pole ratio of the rotor 10 can be obtained.

[0053] FIG. 8 is a diagram showing the configuration of the motor unit according to the embodiment. As shown in FIG. 8, a motor 100 and a control circuit 101 constitute a single motor unit 102. The control circuit 101 is a circuit for controlling the driving of the motor 100. The control circuit 101 detects the position of the rotor 10 using, for example, a known sensorless control technique and generates drive control signals for driving the coils of the motor 100 based on the detection results, thereby controlling the rotation of the motor 100. Here, sensorless control refers to, for example, control that detects an induced voltage generated in the coil 22 of the non-excitation phase of the motor 100, estimates the rotational position of the rotor 10 based on the detection results of the induced voltage, and drives the motor 100 based on the estimation results. The control circuit 101 is realized, for example, by arranging electronic components such as a microcontroller and an inverter circuit on a printed circuit board or the like having multiple wiring and electrically connecting them to each other. The control circuit 101 may be provided inside or outside the casing 50.

[0054] Generally, when a synchronous motor is driven at low speed without a position sensor, a method using induced voltage for initial position estimation does not generate sufficient induced voltage, making it difficult to stably start the synchronous motor without losing synchronism. In contrast, with the motor unit 102 according to this embodiment, as described above, the rotor 10 has high saliency by arranging multiple protrusions 132 on the q axis of the first magnet 11 and the second magnet 12. This makes it possible to detect changes in magnetic flux when estimating the initial position of the magnetic poles during startup under sensorless control of the motor. This allows sufficient induced voltage to be generated even when the synchronous motor is rotating at low speed, making it possible to stably start the synchronous motor without losing synchronism, even when the control circuit 101 drives the synchronous motor without a position sensor.

[0055] The control circuit 101 may be configured as a circuit that performs vector control of the motor 100 as sensorless control.

[0056] As described above, the motor 100 according to the embodiment comprises a rotor 10 having a first magnet 11, a second magnet 12, and a magnetic body 13 located between the first magnet 11 and the second magnet 12 in the direction of the rotation axis, and a stator 20 having a plurality of coils 22, and the magnetic body 13 comprises a ring 131 and a plurality of protrusions 132 protruding from the ring 131 toward the stator 20, and the plurality of protrusions 132 are on the q axis of the first magnet 11 and the second magnet 12.

[0057] According to this, the multiple protrusions 132 are located on the q axis of the first magnet 11 and the second magnet 12, and therefore, in the motor 100 according to the embodiment, it is possible to obtain a synchronous inductance Lq in the q axis direction of the rotor 10 that is greater than the synchronous inductance Ld in the d axis direction of the rotor 10. Due to the multiple protrusions 132, the motor 100 according to the embodiment has a ratio of synchronous inductance Lq / synchronous inductance Ld that is greater than 1, and so-called reverse saliency characteristics are obtained. Furthermore, by providing the plurality of protrusions 132 with reverse saliency characteristics, magnetic saturation by the first magnet 11 and the second magnet 12 is less likely to occur, and the salient pole ratio can be increased even if the thickness of the rotor 10 is small. Furthermore, the motor 100 according to the embodiment has a reverse salient polarity characteristic, which makes it easier to detect changes in inductance, thereby improving the accuracy of estimating the initial position of the magnetic poles of the rotor 10. Therefore, it is possible to provide a surface magnet type synchronous motor 100 that utilizes the reverse saliency of the convex portion 132 and enables sensorless control in the low speed range. Furthermore, compared to embedded magnet synchronous motors, the motor 100 according to the embodiment has a simple structure and is highly productive, making it possible to provide a surface magnet synchronous motor 100 that can be controlled at low speeds at low cost.

[0058] In the motor 100 according to the embodiment, the magnetic body 13 is made of a soft magnetic body.

[0059] By using a soft magnetic material for the magnetic body 13, it is possible to further increase the salient pole ratio of the plurality of protrusions 132.

[0060] In addition, in the motor 100 according to the embodiment, the rotor 10 has a plurality of spaces 14 formed therein, surrounded by the first magnet 11, the second magnet 12, and the magnetic body 13, and the plurality of spaces 14 are arranged between the plurality of protrusions 132 in the circumferential direction.

[0061] This reduces the magnetic permeability in the multiple spaces 14 arranged between the multiple protrusions 132 in the circumferential direction, making it easier for the magnetic flux of the first magnet 11 and the second magnet 12 to pass through the protrusions 132 that form the magnetic path. In addition, the multiple spaces 14 act as flux barriers. That is, a high salient pole ratio of the rotor 10 can be ensured by a simple method.

[0062] In the motor 100 according to the embodiment, non-magnetic materials are disposed in the spaces 14 .

[0063] By disposing a non-magnetic material between the plurality of protrusions 132 and the plurality of spaces 14, it becomes possible to more reliably pass magnetic flux generated between the plurality of protrusions 132 in the circumferential direction. That is, a high salient pole ratio of the rotor 10 can be more reliably ensured.

[0064] In the motor 100 according to the embodiment, the thickness T3 of the magnetic body 13 is smaller than the thickness T1 of the first magnet 11 or the thickness T2 of the second magnet 12 in the axial direction.

[0065] According to this, since the rotor 10 is formed using the magnetic body 13, the salient pole ratio can be increased even if the thickness of the rotor 10 is small.

[0066] The motor unit according to the embodiment includes the motor 100 and a control unit that performs control based on the detected current in one or more coils 22.

[0067] This makes it possible to improve the accuracy of estimating the magnetic pole position of the rotor 10, as described above.

[0068] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0069] For example, the number of poles of the first magnet 11 and the second magnet 12 and the number of slots 212 and magnetic pole portions 213 were not the same, but this is not limited to this, and the number of poles of the first magnet 11 and the second magnet 12 and the number of slots 212 and magnetic pole portions 213 may be the same. [Explanation of symbols]

[0070] 10...rotor, 11...first magnet, 12...second magnet, 13...magnetic material, 14...space, 15...non-magnetic material, 20...stator, 21...magnetic material, 22...coil, 30...shaft, 41...first bearing, 42...second bearing, 50...casing, 100...motor, 131...ring, 132...convex, 211...yoke, 212...slot, 213...magnetic pole portion, 214...spoke, t1...axial thickness of first magnet, t2...axial thickness of second magnet, t3...axial thickness of magnetic material

Claims

1. a rotor having a first magnet, a second magnet, and a magnetic body located between the first magnet and the second magnet in the direction of the rotation axis; a stator having a plurality of coils; Equipped with the magnetic body includes a ring and a plurality of protrusions protruding from the ring toward the stator, the plurality of protrusions are on the q axis of the first magnet and the second magnet; Motor.

2. The magnetic body is formed of a soft magnetic body. The motor according to claim 1 .

3. The rotor has a plurality of spaces surrounded by the first magnet, the second magnet, and the magnetic body, The plurality of spaces are arranged between the plurality of protrusions in the circumferential direction. The motor according to claim 1 .

4. A non-magnetic material is disposed in the plurality of spaces. The motor according to claim 3.

5. In the axial direction, the thickness of the magnetic body is smaller than the thickness of the first magnet or the thickness of the second magnet. The motor according to claim 1 .

6. A motor according to any one of claims 1 to 5; a control unit that performs control based on the detected currents in one or more of the coils; Motor unit.

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