Brushless motor

Abstract

To provide a brushless motor capable of reducing noise and vibration during operation while being flattened and further improving motor performance.SOLUTION: A back yoke 23 has a pair of long-side portions 26 that are arranged to be opposite to each other across a rotation axis A, and a pair of short-side portions 27 that are arranged to be opposite to each other in a direction perpendicular to an opposing direction of the long-side portions 26 across the rotation axis A. The length of the short-side portions 27 along the circumferential direction is shorter than the length of the long-side portions 26 along the circumferential direction. Each tooth 24 has a long-side tooth 33 provided on each of the pair of long-side portions 26, and two short-side teeth 34 provided on each of the pair of short side portions 27. The length LM1 of a long-side winding trunk portion 35 along a radial direction is shorter than the length LM2 of the short-side winding trunk portion 36 along the radial direction, and the length LT1 of the long-side flange portion 37 along the circumferential direction is longer than the length LT2 of the short-side flange portion 38 along the circumferential direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a brushless motor.

Background Art

[0002] For example, an inner rotor type brushless motor includes an annular stator and a rotor rotatably provided at the radial center of the stator. The stator includes a stator core and a coil wound around the stator core. The stator core includes an annular back yoke and a plurality of teeth protruding radially inward from the inner peripheral surface of the back yoke. A coil is wound around each tooth. The rotor includes a rotor shaft that rotates around the rotation axis, a columnar rotor core fixed to the rotor shaft, and a permanent magnet (magnetic pole) provided on the outer peripheral portion of the rotor core. Under such a configuration, when a current is sequentially supplied to a predetermined coil, a predetermined linked magnetic flux is formed in each tooth. This linked magnetic flux serves as a magnetomotive force, and a magnetic attractive force or repulsive force is generated between the permanent magnet. As a result, the rotor is continuously rotated.

[0003] By the way, when such a brushless motor is provided in, for example, a vehicle body, it may be miniaturized by flattening the brushless motor. As a means for flattening the brushless motor, a technique for flattening the stator core has been disclosed (see, for example, Patent Document 1). This one is configured with two linear yokes having a linear shape and two arc-shaped yokes having an arc shape for the back yoke. The linear yokes and the arc-shaped yokes are alternately arranged in the circumferential direction. Teeth protrude from each yoke.

[0004] Since the distances from the rotation axis to each yoke are different, among each tooth, the length of the tooth protruding from the linear yoke and the length of the tooth protruding from the arc-shaped yoke are different. According to Patent Document 1, in order to adjust the magnetic imbalance caused by the difference in the length of these teeth, the length, width, etc. of each part of the stator core are adjusted.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the above-described conventional technology, the size of the space (hereinafter referred to as the winding area) in which the coil is accommodated, which is formed between teeth adjacent in the circumferential direction, varies, and the balance of the magnetomotive force of each coil deteriorates. For this reason, there are problems that the noise and vibration during the drive of the brushless motor deteriorate, and the motor performance deteriorates.

[0007] Therefore, the present invention provides a brushless motor that can reduce noise and vibration during driving while achieving flattening, and further improve motor performance.

Means for Solving the Problems

[0008] In order to solve the above problems, in a first aspect of the present invention, a brushless motor includes an annular stator and a rotor disposed inside the stator in the radial direction and rotatably provided with respect to the stator. The rotor includes a rotor shaft having a rotation axis as its center, a rotor core fixed to the rotor shaft, and a plurality of magnetic poles provided on an outer peripheral portion of the rotor core. The stator includes a stator core and a coil wound around the stator core. The stator core has a flat shape when viewed from the direction of the rotation axis and an annular back yoke, and a plurality of teeth that project radially along the inner peripheral surface of the back yoke toward the inside in the radial direction and around which the coil is wound. The back yoke has a pair of long side portions disposed opposite to each other with the rotation axis interposed therebetween, and a pair of short side portions disposed opposite to each other in a direction orthogonal to the opposing direction of the long side portions with the rotation axis interposed therebetween. The length along the circumferential direction of the short side portions is shorter than the length along the circumferential direction of the long side portions. Each of the teeth projects from the inner peripheral surface of the back yoke and has a winding cylinder portion around which the coil is wound, and a flange portion provided at an end of the winding cylinder portion opposite to the back yoke and extending in the circumferential direction longer than the circumferential width of the winding cylinder portion. Each of the teeth has a long side tooth provided one by one on each of the pair of long side portions, and a short side tooth provided two by two on each of the pair of short side portions. The length along the radial direction of the winding cylinder portion in the long side tooth is shorter than the length along the radial direction of the winding cylinder portion in the short side tooth, and the length along the circumferential direction of the flange portion in the long side tooth is longer than the length along the circumferential direction of the flange portion in the short side tooth.

[0009] By configuring in this way, even when long side teeth and short side teeth of different shapes are mixed, each winding area can be made uniform. Therefore, the balance of the magnetomotive force of each coil can be improved, and noise and vibration when driving the brushless motor can be reduced. The flange portion of the long side tooth, whose winding cylinder portion is shorter than that of the short side tooth, is made longer than the flange portion of the short side tooth. By configuring in this way, the effective magnetic flux of the long side tooth can be increased. Therefore, the motor performance of the brushless motor can be improved.

[0010] In a second aspect of the present invention, in the brushless motor of the first aspect, a straight line connecting the center in the circumferential direction in the drum portion and the rotation axis is defined as a tooth axis, and the angle between the tooth axis of the long-side teeth adjacent in the circumferential direction and the tooth axis of the short-side teeth is defined as θT1. When the angle between the tooth axes of two short-side teeth adjacent in the circumferential direction in one short-side portion is defined as θT2, the angle θT1 and the angle θT2 satisfy θT1 < θT2.

[0011] By configuring in this way, even if the teeth have different shapes, the phases of the induced voltages of the respective coils can be made equidistant. That is, the phases of the respective induced voltages can be made at 120° intervals. For this reason, noise and vibration can be further reduced.

[0012] In a third aspect of the present invention, in the brushless motor of the first aspect or the second aspect, the number of turns of the coil wound around the short-side teeth is larger than the number of turns of the coil wound around the long-side teeth.

[0013] The circumferential length of the flange portion in the short-side teeth is shorter than the circumferential length of the flange portion in the long-side teeth. For this reason, the effective magnetic flux decreases in the short-side teeth. Therefore, by increasing the number of turns of the coil wound around the short-side teeth to be larger than the number of turns of the coil wound around the long-side teeth, the induced voltage can be increased, and the balance of the induced voltages of the respective coils can be improved.

[0014] In a fourth aspect of the present invention, in the brushless motor according to any one of the first to third aspects, the magnetic poles are four poles, the coil has a three-phase structure, the coils are defined as a first-phase coil, a second-phase coil, and a third-phase coil in the order in which current is supplied, the peak value of the current supplied to the first-phase coil is defined as a first peak value, the peak value of the current supplied to the second-phase coil is defined as a second peak value, and the peak value of the current supplied to the third-phase coil is defined as a third peak value. When this is the case, the first-phase coil, the second-phase coil, and the third-phase coil are wound in order in the rotational direction of the rotor around each of the teeth arranged along the circumferential direction, the second-phase coil is wound around the long-side teeth, and the magnitudes C1 of the first peak value, the magnitudes C2 of the second peak value, and the magnitudes C3 of the third peak value satisfy C3 < C1 < C2.

[0015] By providing teeth with different shapes, the harmonic components included in the induced voltage of each phase vary, resulting in torque ripple. Therefore, by configuring the peak values of the current supplied to the coils of each phase in a brushless motor with four poles as described above, the torque ripple generated due to the variation in harmonic components can be offset, and the torque ripple can be reduced.

[0016] In a fifth aspect of the present invention, in the brushless motor according to any one of the first to third aspects, the magnetic poles are eight poles, the coil has a three-phase structure, the coils are defined as a first-phase coil, a second-phase coil, and a third-phase coil in the order in which current is supplied, the peak value of the current supplied to the first-phase coil is defined as a first peak value, the peak value of the current supplied to the second-phase coil is defined as a second peak value, and the peak value of the current supplied to the third-phase coil is defined as a third peak value. When this is the case, the coils are wound in the order of the third-phase coil, the second-phase coil, and the first-phase coil in the rotational direction of the rotor around each of the teeth arranged along the circumferential direction, the second-phase coil is wound around the long-side teeth, and the magnitudes C1 of the first peak value, the magnitudes C2 of the second peak value, and the magnitudes C3 of the third peak value satisfy C1 < C3 < C2.

[0017] By configuring in this way, it is possible to cancel out the torque ripple generated by the variation of the harmonic components in the 8-pole brushless motor, and reduce the torque ripple.

[0018] In the sixth aspect of the present invention, in the brushless motor according to any one of the first to fifth aspects, when viewed from the direction of the rotation axis, the back yoke has a portion overlapping with the region between two straight lines connecting the rotation axis and both circumferential ends of the flange portion extending linearly in a direction orthogonal to the radial direction.

[0019] By flattening the base of the winding drum in this way, a sufficient winding area can be secured. Therefore, the space factor of the coil can be improved, and the motor characteristics of the brushless motor can be improved. Since a sufficient winding area can be secured, the slot openings adjacent to each other in the circumferential direction can also be enlarged. Therefore, it becomes easier to insert a nozzle for winding a coil into the slot, and the winding workability of the coil can be improved.

Advantages of the Invention

[0020] According to the present invention, while achieving the flattening of the brushless motor, it is possible to reduce the noise and vibration during driving, and further improve the motor performance.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0022] Next, embodiments of the present invention will be described with reference to the drawings.

[0023] <Motor with a speed reducer> FIG. 1 is a cross-sectional view of a motor 1 with a speed reducer. As shown in FIG. 1, the motor 1 with a speed reducer includes a motor unit 2 and a speed reduction unit 3 that reduces and outputs the rotation of the motor unit 2. The motor unit 2 and the speed reduction unit 3 are arranged side by side.

[0024] <Speed reduction unit> The speed reduction unit 3 includes a gear case 4 and a worm speed reduction mechanism 5 housed in the gear case 4. The worm speed reduction mechanism 5 includes a worm shaft 6 arranged along the axial direction and a worm wheel 7 meshed with the worm shaft 6. Both ends of the worm shaft 6 in the axial direction are rotatably supported by the gear case 4 via bearings 8a and 8b.

[0025] In the gear case 4, an opening 4a for receiving the motor unit 2 is formed on the side surface closer to the bearing 8b among the two bearings 8a and 8b, on the side closer to the motor unit 2. The end of the worm shaft 6 on the motor unit 2 side protrudes toward the motor unit 2 side through the bearing 8b and the opening 4a. An integral rotor shaft 16 (described later) of the motor unit 2 is formed at the end of the worm shaft 6 on the motor unit 2 side.

[0026] An output shaft 9 is provided at the radial center of the worm wheel 7. The output shaft 9 is arranged coaxially with the rotation axis direction of the worm wheel 7 and protrudes outside the gear case 4 through a bearing boss (not shown) of the gear case 4. A spline connectable to an electrical component (not shown) is formed at the protruding tip of the output shaft 9. Examples of the electrical component include a sunroof, a power window, a power seat, etc. However, it is not limited to this, and the output shaft 9 can be connected to various devices other than the electrical component.

[0027] <Motor unit> The motor unit 2 is a so-called brushless motor that does not require a brush when supplying power to the stator 12. The motor unit 2 includes a motor case 11 provided so as to close the opening 4a of the gear case 4, an annular stator 12 housed in the motor case 11, and a rotor 13 provided on the inner side in the radial direction of the stator 12 and rotatably provided with respect to the stator 12.

[0028] <Motor case> The motor case 11 is formed in a bottomed cylindrical shape. An outer flange portion 11b is formed on the periphery of the opening 11a of the motor case 11. The motor case 11 is fixed to the gear case 4 such that the outer flange portion 11b abuts against the side surface of the gear case 4. A bearing boss 14 protruding to the side opposite to the gear case 4 is formed on the bottom portion 11c of the motor case 11. A bearing 15 for rotatably supporting the rotor 13 is provided on the bearing boss 14.

[0029] <Rotor> Figure 2 is a cross-sectional view taken along line II-II of Figure 1. As shown in FIGS. 1 and 2, the rotor 13 includes a rotor shaft 16 integrally formed with the worm shaft 6, a cylindrical rotor core 17 fitted and fixed to the rotor shaft 16, and a plurality (for example, four in this embodiment) of permanent magnets 18 provided on the outer peripheral surface of the rotor core 17.

[0030] The rotor shaft 16 is arranged coaxially with the worm shaft 6. The end of the rotor shaft 16 on the side opposite to the worm shaft 6 is rotatably supported by the motor case 11 via the bearing 15. In the following description, the direction parallel to the rotation axis A of the rotor shaft 16 and the worm shaft 6 is referred to as the axial direction. The rotation direction of the rotor shaft 16 is referred to as the circumferential direction. The radial direction of the rotor shaft 16, that is, the direction perpendicular to the axial direction and the circumferential direction, is simply referred to as the radial direction.

[0031] The rotor core 17 is formed, for example, by axially laminating a plurality of steel plates. However, it is not limited to this, and the rotor core 17 may be formed, for example, by pressure molding soft magnetic powder. A through hole 17a is formed at the radial center of the rotor core 17. The rotor shaft 16 is inserted or press-fitted into the through hole 17a and fixed. A plurality (for example, four in the present embodiment) of salient poles 19 are provided on the outer peripheral surface 17b of the rotor core 17 at equal intervals in the circumferential direction. The salient poles 19 project outward in the radial direction and extend over the entire axial direction of the rotor core 17.

[0032] The permanent magnet 18 is disposed on the outer peripheral surface of the rotor core 17 and between adjacent salient poles 19 in the circumferential direction. The permanent magnet 18 is formed in an arc shape so as to follow the outer peripheral surface 17b of the rotor core 17 as viewed from the axial direction. The permanent magnet 18 has a smaller curvature radius on the outer peripheral surface than on the inner peripheral surface. For this reason, the permanent magnet 18 has a greater radial thickness at the center in the circumferential direction than at both ends in the circumferential direction. Examples of the permanent magnet 18 include ferrite magnets, neodymium bonded magnets, and neodymium sintered magnets. The permanent magnets 18 are arranged such that the magnetic poles alternate in the circumferential direction.

[0033] Thus, the rotor 13 is a surface magnet (SPM: Surface Permanent Magnet) type rotor having the field permanent magnets 18 on the outer peripheral surface 17b of the rotor core 17, and is an inset type rotor provided with salient poles 19 that project outward in the radial direction of the rotor core 17 between the permanent magnets 18 arranged in the circumferential direction.

[0034] <Stator> The stator 12 includes a stator core 21 formed in an annular shape so as to surround the rotor 13, and a plurality of coils 22 wound around the stator core 21. In FIG. 2, the illustration of the coils 22 is simplified for easier understanding. The stator core 21 is formed, for example, by axially laminating a plurality of steel plates. However, it is not limited to this, and the stator core 21 may be formed, for example, by pressure-molding soft magnetic powder.

[0035] The stator core 21 includes an annular back yoke 23 and six teeth 24 that project radially inward from the inner peripheral surface of the back yoke 23. Between two adjacent teeth 24 in the circumferential direction, sawtooth-shaped slots 25 are respectively formed. Since the number of teeth 24 is six, the number of slots 25 is also six. In the present embodiment, for example, since there are four permanent magnets 18, the number of magnetic poles is four. That is, the motor unit 2 is a four-pole six-slot brushless motor.

[0036] The back yoke 23 is formed in a flat shape when viewed from the axial direction. That is, the back yoke 23 has a pair of long side portions 26 disposed opposite each other with the rotation axis line A interposed therebetween, and a pair of short side portions 27 disposed opposite each other in a direction orthogonal to the opposing direction of the long side portions 26 with the rotation axis line A interposed therebetween. Each long side portion 26 linearly extends in a direction orthogonal to the opposing direction when viewed from the axial direction. The short side portion 27 has a short straight portion 28 that extends in a direction orthogonal to the extending direction of the long side portion 26 when viewed from the axial direction, and a connecting portion 29 that connects the short straight portion 28 and the long side portion 26. The short straight portion 28 and the connecting portion 29 are each linearly formed when viewed from the axial direction. The connecting portion 29 extends by bending from both circumferential ends of the short straight portion 28.

[0037] The length along the circumferential direction of the short side portion 27, that is, the length LS1 of the short straight portion 28 plus the length LS2 of the two connecting portions 29 when viewed from the axial direction, is shorter than the length LL of the long side portion 26 when viewed from the axial direction.

[0038] The teeth 24 are integrally formed with a drum portion 31 that projects along the radial direction from the inner peripheral surface of the back yoke 23, and a flange portion 32 that extends in the circumferential direction from the radially inner end of the drum portion 31. The flange portion 32 is a portion that generates a magnetic attractive force or repulsive force with respect to the permanent magnet 18 of the rotor 13 (details will be described later).

[0039] The six teeth 24 are composed of long-side teeth 33 provided one by one on a pair of long-side portions 26 and short-side teeth 34 provided one by one on each connecting portion 29 of the short-side portion 27. In other words, the short-side teeth 34 are provided two by two on a pair of short-side portions 27 respectively. As a result, the intervals between the respective teeth 33, 34 are set as follows.

[0040] That is, a straight line connecting the rotation axis line A and the circumferential center in the winding drum portion 31, that is, the circumferential center of the winding drum portion 31 is taken as the tooth axis line. Among these, the tooth axis line of the long-side tooth 33 is taken as the tooth axis line STL. The tooth axis line of the short-side tooth 34 is taken as the tooth axis line STS. Let the angle between the tooth axis line STL of the long-side tooth 33 and the tooth axis line STS of the short-side tooth 34 adjacent in the circumferential direction be θT1. Let the angle between the respective tooth axis lines STS of the short-side teeth 34 adjacent in the circumferential direction in one short-side portion 27 be θT2. At this time, the angle θT1 and the angle θT2 satisfy θT1 < θT2 ···(1) and satisfy this condition.

[0041] Among the winding drum portion 31, the length LM1 along the radial direction of the long-side winding drum portion 35 of the long-side tooth 33 is shorter than the length LM2 along the radial direction of the short-side winding drum portion 36 of the short-side tooth 34. On the other hand, among the flange portions 32, the length LT1 along the circumferential direction of the long-side flange portion 37 of the long-side tooth 33 is longer than the length LT2 along the circumferential direction of the short-side flange portion 38 of the short-side tooth 34. In other words, the magnetic flux convergence angle θC1 of the long-side flange portion 37 is larger than the magnetic flux convergence angle θC2 of the short-side flange portion 38. The magnetic flux convergence angle is the angle between two straight lines SC passing through the rotation axis line A and both circumferential ends of the flange portion 32.

[0042] The region of the magnetic flux convergence angle θC1 of the long-side flange portion 37 overlaps only with the long-side portion 26. The region of the magnetic flux convergence angle θC2 of the short-side flange portion 38 overlaps only with the connecting portion 29 of the short-side portion 27. That is, the back yoke 23 extends linearly in a direction orthogonal to the radial direction at a location overlapping with the region between the two straight lines SC connecting the rotational axis A and both circumferential ends of the flange portion 32 as viewed from the axial direction.

[0043] Figure 3 is a wiring diagram of the coil 22. As shown in Figure 3, the coil 22 is wound around each tooth 24 in a concentrated winding method. Each coil 22 is connected by a △ (delta) connection method. Among the coils 22, the number of turns of the coil 22 wound around the short-side teeth 34 is larger than the number of turns of the coil 22 wound around the long-side teeth 33.

[0044] <Operation of the motor with a speed reducer> Next, the operation of the motor 1 with a speed reducer will be described. The motor 1 with a speed reducer includes a controller (not shown) that selectively supplies current to each coil 22. When current is selectively supplied to each coil 22 through this controller, a linked magnetic flux is formed in a predetermined tooth 24. The linked magnetic flux flows from the flange portion 32 of each tooth 24 toward the rotor 13, and generates a magnetic attractive force or repulsive force (magnet torque) with the effective magnetic flux formed by the permanent magnet 18 of the rotor 13. In addition, the salient pole 19 of the rotor core 17 generates a reluctance torque that rotates the rotor core 17 so that the protruding direction is the direction in which the linked magnetic flux from each flange portion 32 easily flows and the magnetic resistance (reluctance) of the magnetic path of the linked magnetic flux is reduced.

[0045] These magnetic torques and reluctance torques continuously rotate the rotor 13. The rotation of the rotor 13 is transmitted to the worm shaft 6 integrated with the rotor shaft 16. Further, it is transmitted to the worm wheel 7 meshed with the worm shaft 6. The rotation of the worm wheel 7 is transmitted to the output shaft 9 connected to the worm wheel 7. The desired electrical components are driven by the rotation of the output shaft 9.

[0046] <Method of energization control for each coil> The above-described motor unit 2 is formed in a flat shape when viewed from the axial direction of the back yoke 23, and accordingly, the teeth 24 are composed of long-side teeth 33 and short-side teeth 34. Therefore, among the coils 22, the number of turns of the coil 22 wound around the short-side teeth 34 is made larger than the number of turns of the coil 22 wound around the long-side teeth 33. Further, the method of energization control for each coil 22 is as follows.

[0047] That is, when the rotation direction of the rotor 13 is the direction of the arrow CCW shown in FIG. 2, as shown in FIGS. 2 and 3, the coils 22 are set as the first-phase coil, the second-phase coil, and the third-phase coil in the order in which current is supplied. In the present embodiment, the first-phase coil is, for example, the U-phase coils U1, U2 (the first U-phase coil U1, the second U-phase coil U2). The second-phase coil is, for example, the V-phase coils V1, V2 (the first V-phase coil V1, the second V-phase coil V2). The third-phase coil is, for example, the W-phase coils W1, W2 (the first W-phase coil W1, the second W-phase coil W2). In the following description, the coil 22 or each phase coil U1 to W2 will be selectively used for explanation as necessary, but they are the same coil.

[0048] The first U-phase coil U1, the first V-phase coil V1, and the first W-phase coil W1 are wound in order in the direction of arrow CCW around the respective teeth 24 adjacent to each other in the circumferential direction. At this time, the first V-phase coil V1 is wound around the long-side tooth 33. The same applies to the second U-phase coil U2, the second V-phase coil V2, and the second W-phase coil W2. That is, the second U-phase coil U2, the second V-phase coil V2, and the second W-phase coil W2 are wound in order in the direction of arrow CCW around the respective teeth 24 adjacent to each other in the circumferential direction. At this time, the second V-phase coil V2 is wound around the long-side tooth 33.

[0049] Here, let the peak value of the current supplied to the first U-phase coil U1 and the second U-phase coil U2, which are the first-phase coils, be the first peak value. Let the peak value of the current supplied to the first V-phase coil V1 and the second V-phase coil V2, which are the second-phase coils, be the second peak value. Let the peak value of the current supplied to the first W-phase coil W1 and the second W-phase coil W2, which are the third-phase coils, be the third peak value. At this time, the magnitudes C1 of the first peak value, C2 of the second peak value, and C3 of the third peak value satisfy C3 < C1 < C2 ···(2) and meet the requirement.

[0050] The magnitudes C1 to C3 of each peak value can be controlled, for example, by changing the pulse width when the energization control of the current supplied to the coil 22 is PWM (Pulse Width Modulation) control. In addition, the magnitudes C1 to C3 of each peak value can be controlled by, for example, changing the applied voltage to the coil 22 or varying the resistance value with a controller (not shown).

[0051] <Actions and effects of each component> Next, the actions and effects of each component will be described. The above-mentioned motor unit 2 is formed with a flat shape when viewed in the axial direction of the back yoke 23, and the teeth 24 are composed of long-side teeth 33 and short-side teeth 34. The length LM1 along the radial direction of the long-side winding cylinder portion 35 is shorter than the length LM2 along the radial direction of the short-side winding cylinder portion 36. On the other hand, the length LT1 along the circumferential direction of the long-side flange portion 37 is longer than the length LT2 along the circumferential direction of the short-side flange portion 38. By configuring in this way, even when long-side teeth 33 and short-side teeth 34 with different shapes are mixed, the winding area CA1 of the long-side teeth 33 and the winding area CAs of the short-side teeth 34 (the portions shown shaded in FIG. 2 respectively) can be made uniform. Therefore, the balance of the magnetomotive force of each coil 22 can be improved, and the noise and vibration when driving the motor unit 2 can be reduced.

[0052] Moreover, since the length LT1 along the circumferential direction of the long-side flange portion 37 is longer than the length LT2 along the circumferential direction of the short-side flange portion 38, even if the length LM1 along the radial direction of the long-side winding cylinder portion 35 is shorter than the length LM2 along the radial direction of the short-side winding cylinder portion 36, the effective magnetic flux of the long-side teeth 33 can be increased. Therefore, the motor performance of the motor unit 2 can be improved.

[0053] The angle θT1 between the tooth axis STL of the long-side teeth 33 and the tooth axis STS of the short-side teeth 34 adjacent in the circumferential direction, and the angle θT2 between the tooth axes STS of the short-side teeth 34 adjacent in the circumferential direction in one short-side portion 27 satisfy the above formula (1). Here, the length LT1 along the circumferential direction of the long-side flange portion 37 is longer than the length LT2 along the circumferential direction of the short-side flange portion 38. In such a case, since the waveforms of the induced voltages at each flange portion 37, 38 are different, if each tooth 33, 34 is provided at equal intervals in the circumferential direction, the phases of the induced voltages of each phase coil U1~W2 will not be at 120° intervals (uniform). Therefore, by providing the angle θT1 and the angle θT2 so as to satisfy the above formula (1), the phases of the induced voltages of each phase coil U1~W2 can be made at equal intervals. That is, the phases of each induced voltage can be at 120° intervals. For this reason, the noise and vibration can be further reduced.

[0054] In addition, among the coils 22, the number of turns of the coil 22 wound around the short-side teeth 34 is larger than the number of turns of the coil 22 wound around the long-side teeth 33. Here, since the length LT2 along the circumferential direction of the short-side flange portion 38 is shorter than the length LT1 along the circumferential direction of the long-side flange portion 37, the effective magnetic flux of the short-side flange portion 38 decreases as compared with the long-side flange portion 37. Therefore, by making the number of turns of the coil 22 wound around the short-side teeth 34 larger than the number of turns of the coil 22 wound around the long-side teeth 33, the induced voltage of the coil 22 wound around the short-side teeth 34 can be increased. For this reason, the balance of the induced voltages of the coils 22 can be improved.

[0055] FIG. 4 is a graph showing the change (waveform) of the induced voltage of the coils 22 of each phase when the vertical axis represents the induced voltage [V] of the coils 22 of each phase and the horizontal axis represents the rotation angle [deg]. As shown in FIG. 4, in the stator 12 of the present embodiment, it can be confirmed that the waveforms of the induced voltages of the coils 22 of each phase are sine waves of the same magnitude with phases at intervals of 120°.

[0056] In addition, the peak values C1 to C3 of the currents supplied to the phase coils U1 to W2 satisfy the above formula (2). Here, by configuring the teeth 24 with the long-side teeth 33 and the short-side teeth 34 having different shapes, the harmonic components included in the induced voltages of the phase coils U1 to W2 vary, and torque ripple occurs. More specifically, since the number of poles of the motor unit 2 of the present embodiment is 4 poles, the torque ripple of the 4th component increases. Therefore, in the motor unit 2 having 4 poles, by configuring the peak values C1 to C3 of the currents supplied to the phase coils U1 to W2 so as to satisfy the above formula (2), the torque ripple generated by the variation of the harmonic components can be offset, and the torque ripple can be reduced.

[0057] FIG. 5 is a graph showing the change in the torque of the rotor 13 when the vertical axis represents the torque [Nm] of the rotor 13 and the horizontal axis represents the rotation angle [deg]. As shown in FIG. 5, it can be confirmed that in this embodiment, the fluctuation of torque ripple can be reduced as compared with the conventional case.

[0058] The back yoke 23 extends linearly in a direction orthogonal to the radial direction at a location overlapping with a region between two straight lines SC connecting the rotation axis line A and both circumferential ends in the flange portion 32 when viewed from the axial direction. In this way, by flattening the base of each winding cylinder portion 35, 36, a sufficient winding area can be secured. For this reason, the occupation ratio of the coil 22 can be improved, and the motor characteristics of the motor portion 2 can be improved. Since a sufficient winding area can be secured, the opening width on the radially inner side in the slot 25 can be increased. For this reason, it becomes easy to insert a nozzle (not shown) for winding the coil 22 into the slot 25, and the winding workability of the coil 22 can be improved. The nozzle is a nozzle for feeding out the coil 22 provided in a winding device (flyer) for winding the coil 22 around each tooth 24.

[0059] Since it is possible to reduce the noise and vibration when driving the motor portion 2 and improve the motor performance of the motor portion 2, it contributes to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure access for all people to affordable, reliable, and sustainable modern energy", and Goal 9, "Foster resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation".

[0060] [Modification Example] The present invention is not limited to the above-described embodiment, and includes those obtained by making various changes to the above-described embodiment without departing from the gist of the present invention.

[0061] For example, in the above-described embodiment, the case where the motor portion 2 is a brushless motor with 4 poles and 6 slots has been described. However, the present invention is not limited to this, and the motor portion 2 may be a brushless motor with 8 poles and 6 slots. In this case, the magnitudes C1 to C3 of the peak values of the currents supplied to the phase coils U1 to W2 are C1 < C3 < C2 ···(3) It satisfies the above. By configuring in this way, the same effects as those of the above-described embodiments can be achieved.

[0062] In the above-described embodiment, the case where the rotation direction of the rotor 13 is the direction of the arrow CCW shown in FIG. 2 has been described. However, it is not limited to this, and the rotation direction of the rotor 13 may be the direction of the arrow CW shown in FIG. 2. In this case, the winding order of each phase coil U1 to W2 may also be in the order of the arrow CW.

[0063] Also, it is possible to set the rotation direction of the rotor 13 to the arrow CW without changing the winding order of each phase coil U1 to W2 from that of the above-described embodiment. In this case, for example, the first-phase coil is set as the W-phase coil, and the third-phase coil is set as the U-phase coil. That is, the peak value of the current supplied to the first W-phase coil W1 and the second W-phase coil W2, which are the first-phase coils, is defined as the first peak value. The peak value of the current supplied to the first V-phase coil V1 and the second V-phase coil V2, which are the second-phase coils, is defined as the second peak value. The peak value of the current supplied to the first U-phase coil U1 and the second U-phase coil U2, which are the third-phase coils, is defined as the third peak value.

[0064] At this time, in the 4-pole 6-slot motor unit 2, the magnitude C1 of the first peak value, the magnitude C2 of the second peak value, and the magnitude C3 of the third peak value satisfy the above formula (2). In the 8-pole 6-slot motor unit 2, the magnitude C1 of the first peak value, the magnitude C2 of the second peak value, and the magnitude C3 of the third peak value satisfy the above formula (3).

[0065] In the above-described embodiment, the case where each long-side portion 26 linearly extends in a direction orthogonal to the facing direction when viewed from the axial direction has been described. The short-side portion 27 has been described in the case of having a short straight-line portion 28 that extends in a direction orthogonal to the extending direction of the long-side portion 26 when viewed from the axial direction, and a connecting portion 29 that connects the short straight-line portion 28 and the long-side portion 26. The case where the short straight-line portion 28 and the connecting portion 29 are each linearly formed when viewed from the axial direction has been described. The case where the connecting portion 29 extends by bending from both circumferential ends of the short straight-line portion 28 has been described.

[0066] However, it is not limited to this. The back yoke 23 is formed in a flat shape when viewed from the axial direction, and it is only necessary that the length along the circumferential direction of the short side portion 27 is shorter than the length along the circumferential direction of the long side portion 26. For example, the long side portion 26 may be formed by bending. It is sufficient if the six teeth 24 are constituted by long side teeth 33 provided one by one on a pair of long side portions 26 and short side teeth 34 provided two by two on a pair of short side portions 27.

[0067] In the above-described embodiment, the motor unit 2 has been described in the case where it is provided in the motor 1 with a speed reducer. However, it is not limited to this. It is also possible to use the motor unit 2 alone, and it is possible to adopt the motor unit 2 in various devices.

Explanation of reference numerals

[0068] 1… Motor with speed reducer, 2… Motor section (brushless motor), 3… Speed reduction section, 4… Gear case, 4a… Opening, 5… Worm speed reduction mechanism, 6… Worm shaft, 7… Worm wheel, 8a… Bearing, 8b… Bearing, 9… Output shaft, 11… Motor case, 11a… Opening, 11b… Outer flange section, 11c… Bottom, 12… Stator, 13… Rotor, 14… Bearing boss, 15… Bearing, 16… Rotor shaft, 17… Rotor core, 17a… Through hole, 17b… Outer peripheral surface, 18… Permanent magnet (magnetic pole), 19… Salient pole, 21… Stator core, 22… Coil, 23… Back yoke, 24… Teeth, 25… Slot, 26… Long side section, 27… Short side section, 28… Short straight section, 29… Connecting section, 31… Winding drum section, 32… Flange section, 33… Long side teeth, 34… Short side teeth, 35… Long side winding drum section, 36… Short side winding drum section, 37… Long side flange section, 38… Short side flange section, A… Axis of rotation, C1… Magnitude of the first wave height value, C2… Magnitude of the second wave height value, C3… Magnitude of the third wave height value, CCW… Arrow, CW… Arrow, LL, LM1, LM2, LS1, LS2, LT1, LT2… Lengths, SC… Straight line, STL… Axis of the long side teeth, STS… Axis of the short side teeth, U1… First U-phase coil, U2… Second U-phase coil, V1… First V-phase coil, V2… Second V-phase coil, W1… First W-phase coil, W2… Second W-phase coil, θC1… Magnetic flux convergence angle, θC2… Magnetic flux convergence angle, θT1, θT2… Angles

Claims

1. An annular stator, a rotor disposed radially inside the stator and rotatably provided with respect to the stator, and the rotor includes a rotor shaft having a rotation axis as its axis, a rotor core fixed to the rotor shaft, and a plurality of magnetic poles provided on an outer peripheral portion of the rotor core, and the stator includes a stator core, and a coil wound around the stator core, and the stator core is flat and annular when viewed from the direction of the rotation axis, and an annular back yoke, a plurality of teeth protruding radially inward along the radial direction from an inner peripheral surface of the back yoke, around which the coil is wound, and the back yoke has a pair of long side portions disposed opposite to each other with the rotation axis interposed therebetween, and a pair of short side portions disposed opposite to each other in a direction orthogonal to the opposing direction of the long side portions with the rotation axis interposed therebetween, and a length along the circumferential direction of the short side portions is shorter than a length along the circumferential direction of the long side portions, each of the teeth protrudes from the inner peripheral surface of the back yoke and has a winding cylinder portion around which the coil is wound, and a flange portion provided at an end of the winding cylinder portion opposite to the back yoke, extending in the circumferential direction and longer than the circumferential width of the winding cylinder portion, and each of the teeth includes long side teeth respectively provided one by one on the pair of long side portions, and short side teeth respectively provided two by two on the pair of short side portions, and The length along the radial direction of the winding cylinder portion in the long-side teeth is shorter than the length along the radial direction of the winding cylinder portion in the short-side teeth. The length along the circumferential direction of the flange portion in the long-side teeth is longer than the length along the circumferential direction of the flange portion in the short-side teeth. A brushless motor characterized by the above.

2. A straight line connecting the center in the circumferential direction in the winding cylinder portion and the rotation axis is defined as the tooth axis. Let the angle between the tooth axes of the adjacent long-side teeth and the tooth axes of the short-side teeth in the circumferential direction be θT1, and let the angle between the tooth axes of the two adjacent short-side teeth in the circumferential direction in one short-side portion be θT2. The angle θT1 and the angle θT2 are θT1 < θT2 satisfying The brushless motor according to claim 1, characterized by the above.

3. The number of turns of the coil wound around the short-side teeth is more than the number of turns of the coil wound around the long-side teeth. The brushless motor according to claim 1 or claim 2, characterized by the above.

4. The magnetic poles are four poles. The coil has a three-phase structure. Let the coils be the first-phase coil, the second-phase coil, and the third-phase coil in the order in which current is supplied. Let the peak value of the current supplied to the first-phase coil be the first peak value, the peak value of the current supplied to the second-phase coil be the second peak value, and the peak value of the current supplied to the third-phase coil be the third peak value. The first-phase coil, the second-phase coil, and the third-phase coil are wound in order in the rotation direction of the rotor around each of the teeth arranged along the circumferential direction, and the second-phase coil is wound around the long-side teeth. The magnitude C1 of the first peak value, the magnitude C2 of the second peak value, and the magnitude C3 of the third peak value are C3 < C1 < C2 satisfying The brushless motor according to claim 1 or claim 2, characterized in that.

5. The magnetic poles are 8 poles, The coil has a three-phase structure, When the coils are the first-phase coil, the second-phase coil, and the third-phase coil in the order in which current is supplied, and the peak value of the current supplied to the first-phase coil is the first peak value, the peak value of the current supplied to the second-phase coil is the second peak value, and the peak value of the current supplied to the third-phase coil is the third peak value, The coils are wound in the order of the third-phase coil, the second-phase coil, and the first-phase coil in the rotational direction of the rotor in each of the teeth arranged along the circumferential direction, and the second-phase coil is wound around the long-side teeth, The magnitude C1 of the first peak value, the magnitude C2 of the second peak value, and the magnitude C3 of the third peak value are C1 < C3 < C2 satisfying The brushless motor according to claim 1 or claim 2, characterized in that.

6. When viewed from the direction of the rotation axis, a portion of the back yoke overlapping with the region between two straight lines connecting the rotation axis and both circumferential ends of the flange portion extends linearly in a direction orthogonal to the radial direction. The brushless motor according to claim 1 or claim 2, characterized in that.

Images