Rotating electric machine

Abstract

To provide a rotary electric machine that can reduce noise and vibration.SOLUTION: A rotor 9 includes: a shaft 31 that rotates around a rotation axis C1; a rotor core 32 fixed coaxially on the shaft 31; a plurality of permanent magnets 33 arranged on an outer peripheral surface 32b of the rotor core 32; and a plurality of salient poles 35 provided on the outer peripheral surface 32b of the rotor core 32 and protruding from the outer peripheral surface 32b radially outward. The salient poles 35 have a first salient pole 91 with the position of a radially outward leading end 91a located radially outward relative to an outer peripheral corner 33f of the permanent magnet 33, and a second salient pole 92 with the position of a radially outward leading end 92a located radially inward relative to the outer peripheral corner 33f of the permanent magnet 33. The first salient pole 91 and the second salient pole 92 are alternately arranged in a circumferential direction.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a rotating electric machine.

Background Art

[0002] As a rotating electric machine, for example, an electric motor can be mentioned. The electric motor includes a stator, and a rotor provided rotatably about a rotation axis with respect to the stator. The stator includes a plurality of teeth around which coils are wound. Slots are formed between adjacent teeth in the circumferential direction. Through these slots, coils are wound around each tooth. Some rotors include a rotor core and a plurality of permanent magnets for field excitation provided on the rotor core. When an electric current is applied to the coil, an interlinking magnetic flux is formed in the teeth. A magnetic attractive force or repulsive force is generated between this interlinking magnetic flux and the permanent magnets of the rotor, and the rotor is continuously rotated.

[0003] Among this type of rotor, there is a surface magnet (SPM: Surface Permanent Magnet) type rotor in which permanent magnets are arranged side by side in the circumferential direction on the outer peripheral surface of the rotor core. Among this surface magnet type rotor, there is a so-called inset type rotor provided with a plurality of salient poles that protrude radially outward from the outer peripheral surface of the rotor core and are arranged between adjacent permanent magnets in the circumferential direction.

[0004] In an inset type rotor, the rotor core and the salient poles are formed of a magnetic material. Since the salient poles of the rotor core protrude in the radially outward direction, it becomes a direction in which the interlinking magnetic flux of the stator easily flows. Further, the salient poles generate a reluctance torque that rotates the rotor core so as to reduce the magnetic resistance (reluctance) of the magnetic path of the interlinking magnetic flux.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in inset rotors, the formation of salient poles increases the distortion of the magnetic field on the outer surface of the rotor, which could potentially increase torque ripple. In particular, the order component of torque ripple that is the least common multiple of the number of magnetic poles and the number of slots tended to become significantly larger. This could potentially lead to increased noise and vibration in the electric motor.

[0007] Therefore, the present invention provides a rotating electric machine that can reduce noise and vibration. [Means for solving the problem]

[0008] To solve the above problems, in a first aspect of the present invention, a rotating electric machine comprises a stator core having a plurality of teeth around which a coil is wound, and a rotor rotatably provided radially inward from the plurality of teeth, wherein the rotor comprises a shaft that rotates around the axis of rotation, a rotor core fixed coaxially to the shaft, a plurality of permanent magnets arranged on the outer circumferential surface of the rotor core, and a plurality of salient poles provided on the outer circumferential surface of the rotor core and projecting radially outward from the outer circumferential surface, wherein the plurality of salient poles are arranged between adjacent permanent magnets in the circumferential direction on the outer circumferential surface of the rotor core, and the plurality of salient poles include a first salient pole whose radially outward tip is located radially outward from the corners on both sides of the circumferential surface of the permanent magnet, and a second salient pole whose radially outward tip is located radially inward from the corners of the permanent magnet, wherein the first salient poles and the second salient poles are arranged alternately in the circumferential direction.

[0009] This configuration suppresses the significant increase in specific order components of the torque ripple. As a result, noise and vibration of the rotating electric machine can be reduced.

[0010] In a second aspect of the present invention, in the rotating electric machine of the first aspect, the tip of the first salient pole may be located radially outward from the corner of the permanent magnet and radially inward from the inner circumferential surface of the stator core.

[0011] This configuration allows for a reduction in the motor torque performance of the rotating electric machine while reliably reducing noise and vibration.

[0012] In a third aspect of the present invention, in the rotating electric machine of the first or second aspect, the tip of the second salient pole may be located radially outward from the central position between the corner of the permanent magnet and the base of the salient pole, and radially inward from the corner of the permanent magnet.

[0013] This configuration allows for a reduction in the motor torque performance of the rotating electric machine while reliably reducing noise and vibration.

[0014] In a fourth aspect of the present invention, in a rotating electric machine according to any one of the first to third aspects, the arc center of the inner circumferential surface of the permanent magnet and the arc center of the outer circumferential surface of the permanent magnet are located on a straight line passing through the axis of rotation and the circumferential center of the permanent magnet, and the arc center of the outer circumferential surface may be located radially outward with respect to the arc center of the inner circumferential surface.

[0015] This configuration allows the circumferential center of the permanent magnet to protrude radially outward more than the circumferential sides. Therefore, even if the tip of the first salient pole protrudes radially outward more than the radially outward end of the circumferential side surface of the permanent magnet, the clearance between the permanent magnet and the teeth can be kept as small as possible. Thus, it is possible to reliably reduce noise and vibration of the rotating electric machine while reliably suppressing a reduction in the motor torque performance of the rotating electric machine. [Effects of the Invention]

[0016] According to the present invention, noise and vibration of rotating electric machines can be reduced. [Brief explanation of the drawing]

[0017] [Figure 1] This is a perspective view of the motor with a speed reducer according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along line II-II of FIG. 1. [Figure 3] This is a cross-sectional view along the radial direction of the stator and the rotor according to an embodiment of the present invention. [Figure 4] This is an enlarged view of part IV of FIG. 3. [Figure 5] This is an explanatory view of the radial length of the second salient pole according to an embodiment of the present invention. [Figure 6] This is a graph showing the change in torque of the rotor according to an embodiment of the present invention. [Figure 7] This is a graph comparing the order components of the torque ripple and the magnitude of the torque ripple for each order component with a conventional rotor according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0018] Next, embodiments of the present invention will be described based on the drawings.

[0019] <Motor with a Speed Reducer> FIG. 1 is a perspective view of the motor 1 with a speed reducer. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. The motor 1 with a speed reducer is, for example, a drive source for a wiper mounted on a vehicle. The motor 1 with a speed reducer includes an electric motor 2, a speed reduction unit 3 that reduces and outputs the rotation of the electric motor 2, and a controller unit 4 that controls the driving of the electric motor 2.

[0020] In the following description, when simply referring to the "axial direction", it means the direction parallel to the central axis (rotation axis line C1 of the electric motor 2) on the shaft 31 of the electric motor 2. When simply referring to the "circumferential direction", it means the circumferential direction (rotation direction) of the shaft 31. When simply referring to the "radial direction", it means the radial direction of the shaft 31 that is orthogonal to the axial direction and the circumferential direction.

[0021] <Electric motor> The electric motor 2 comprises a motor case 5, a cylindrical stator 8 housed within the motor case 5, and a rotor 9 provided radially inward of the stator 8 and rotatably mounted relative to the stator 8. The electric motor 2 is a so-called brushless motor that does not require brushes to supply power to the stator 8.

[0022] <Motor Case> The motor case 5 is made of a material with excellent heat dissipation properties, such as aluminum die-cast. The motor case 5 consists of a first motor case 6 and a second motor case 7, which are configured to be separable in the axial direction. The first motor case 6 and the second motor case 7 are each formed in a bottomed cylindrical shape. The first motor case 6 is integrally molded with the gear case 40 of the reduction unit 3 such that its bottom portion 10 is joined to the gear case 40. A through hole 10a is formed in the radial center of the bottom portion 10, through which the shaft 31 of the rotor 9 can be inserted.

[0023] An outer flange portion 16 is formed in the opening 6a of the first motor case 6, extending radially outward. An outer flange portion 17 is formed in the opening 7a of the second motor case 7, extending radially outward. These outer flange portions 16 and 17 are brought together to form a motor case 5 with an internal space. A stator 8 is arranged in the internal space of the motor case 5 so as to fit inside the first motor case 6 and the second motor case 7.

[0024] <Stata> Figure 3 is a cross-sectional view along the radial direction of the stator 8 and rotor 9. As shown in Figures 2 and 3, the stator 8 comprises a stator core 20, a resin insulator 23 mounted on the stator core 20, and a coil 24 wound around the stator core 20 over the insulator 23.

[0025] The stator core 20 is integrally molded with a cylindrical core portion 21 arranged coaxially with the rotation axis C1 and a plurality of teeth 22 (for example, six in this embodiment) projecting radially inward from the core portion 21. The stator core 20 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction. However, it is not limited to this, and the stator core 20 may also be formed, for example, by pressure molding soft magnetic powder.

[0026] Each tooth 22 comprises an integrally molded tooth body 22a and a flange portion 22b. The tooth body 22a protrudes radially inward from the inner circumferential surface of the core portion 21. The flange portion 22b extends radially outward from the radially inner end of the tooth body 22a. The flange portion 22b is circumferential and constitutes the inner circumference of the stator core 20. Dovetail-shaped slots 19 are formed between adjacent teeth 22 in the circumferential direction. The insulator 23 is formed to cover the stator core 20. The insulator 23 provides insulation between the stator core 20 and the coil 24.

[0027] <Rotor> The rotor 9 is rotatably mounted radially inward of the stator 8 with a small gap between them. The rotor 9 comprises a shaft 31 that rotates around a rotation axis C1, a rotor core 32 fixed to the shaft 31, and four permanent magnets 33 for field magnetism attached to the rotor core 32. Thus, the electric motor 2 has four magnetic poles for the permanent magnets 33 and six slots 19 (teeth 22), and is composed of four poles and six slots.

[0028] The shaft 31 is integrally molded with the worm shaft 44 (see Figure 2), which will be described later and constitutes the reduction gear 3. The rotor core 32 is fitted and fixed to the outer circumferential surface of the shaft 31. The rotor core 32 is formed in a cylindrical shape and is arranged coaxially with the rotation axis C1. The rotor core 32 is formed by laminating a plurality of electromagnetic steel sheets in the axial direction. However, it is not limited to this, and the rotor core 32 may be formed, for example, by pressure molding soft magnetic powder.

[0029] A through-hole 32a is formed in the radial center of the rotor core 32, extending axially. The shaft 31 is press-fitted into the through-hole 32a. However, this is not the only option; the rotor core 32 may also be fitted onto the outer circumferential surface of the shaft 31 and fixed to the shaft 31 with an adhesive or the like. Four salient poles 35 are provided on the outer circumferential surface 32b of the rotor core 32 at equal intervals in the circumferential direction. The salient poles 35 protrude radially outward, along the radial direction when viewed from the axial direction. The salient poles 35 extend along the entire axial direction of the rotor core 32.

[0030] The salient pole 35 has a first salient pole 91 and a second salient pole 92. Viewed from the axial direction, the radial length of the first salient pole 91 is longer than the radial length of the second salient pole 92. Details of the lengths of each salient pole 91 and 92 will be described later. The first salient pole 91 and the second salient pole 92 are arranged alternately in the circumferential direction. The first salient pole 91 and the second salient pole 92 differ only in their radial length when viewed from the axial direction; their other shapes are identical. For this reason, in the following description, the identical parts of the first salient pole 91 and the second salient pole 92 will be collectively referred to as salient pole 35.

[0031] The salient pole 35 is formed such that two opposing sides 35a in the circumferential direction are parallel. In other words, the salient pole 35 is formed so that its width dimension in the circumferential direction is uniform. A chamfered portion 35b is formed at the corners on both sides of the radially outer side of the salient pole 35 in the circumferential direction. A rounded chamfered portion 35c is formed at the base of the salient pole 35 so as to widen towards the radially inward direction. On the outer circumferential surface 32b of the rotor core 32 formed in this way, the space between two adjacent salient poles 35 in the circumferential direction is configured as a magnet housing portion 36.

[0032] In other words, the rotor 9 is a surface permanent magnet (SPM) type rotor in which permanent magnets 33 are arranged on the outer circumferential surface 32b of the rotor core 32, and is an inset type rotor equipped with salient poles 35 between the permanent magnets 33 arranged in the circumferential direction. The four permanent magnets 33 are each located in a magnet housing 36. Each permanent magnet 33 is fixed to the rotor core 32 in the magnet housing 36, for example, by adhesive. The permanent magnets 33 are, for example, ferrite magnets, neodymium bonded magnets, or neodymium sintered magnets.

[0033] The permanent magnets 33 are magnetized, for example, so that the orientation of the magnetization (magnetic field) is parallel along the thickness direction. In other words, the orientation of the permanent magnets 33 is a parallel orientation in which the easy magnetization direction is parallel to the radial direction in the central part of the permanent magnet 33. Adjacent permanent magnets 33 in the circumferential direction are arranged so that their magnetization directions are opposite to each other.

[0034] The four permanent magnets 33 are arranged so that their magnetic poles are staggered in the circumferential direction. In other words, the permanent magnet 33 with the north pole on the outer circumference and the permanent magnet 33 with the south pole on the outer circumference are arranged to be adjacent to each other in the circumferential direction. As a result, the salient poles 35 of the rotor core 32, which are positioned between the circumferentially adjacent permanent magnets 33, are located at the magnetic pole boundaries (polar boundaries).

[0035] Figure 4 is an enlarged view of section IV of Figure 3. As shown in Figure 4, in the permanent magnet 33, the arc center Ci of the radially inner inner circumferential surface 33b coincides with the position of the rotation axis C1. In the permanent magnet 33, the arc center Co of the radially outer circumferential surface 33a is eccentric with respect to the rotation axis C1 of the shaft 31. Specifically, the arc center Co of the circumferential surface 33a of the permanent magnet 33 is located radially outward from the rotation axis C1 on a straight line L1 passing through the rotation axis C1 and the circumferential central part 33c of the permanent magnet 33.

[0036] As a result, the radial thickness of the permanent magnet 33 gradually increases from both sides in the circumferential direction toward the central part 33c. Consequently, the gap between the outer surface 33a of the permanent magnet 33 and the inner surface 22c of the teeth 22 (the inner surface of the flange portion 22b, the inner surface of the stator core 20) gradually decreases from both sides in the circumferential direction toward the central part 33c. The radial thickness of the permanent magnet 33 is greater than the radial thickness of the rotor core 32. For example, the radial thickness Rm of the circumferential central portion 33c of the permanent magnet 33 is greater than the radial thickness Rc of the circumferential central portion 32c of the rotor core 32.

[0037] Almost the entire inner circumferential surface 33b of the permanent magnet 33 is in contact with the outer circumferential surface 32b of the rotor core 32. Each surface on both sides of the permanent magnet 33 in the circumferential direction has a side surface 33d facing the salient pole 35 in the circumferential direction, a connecting surface 33e connecting the side surface 33d to the outer circumferential surface 33a, and an arcuate surface 33h connecting the side surface 33d to the inner circumferential surface 33b. The side surface 33d is formed flat and almost parallel to the side surface 35a of the salient pole 35.

[0038] The connecting surface 33e is a so-called flat surface and is formed to be flat. That is, the connecting surface 33e is formed to gradually move away from the salient pole 35 as it extends radially outward from the salient pole 35. In other words, the connecting surface 33e is formed to change the radial thickness of the permanent magnet 33 to gradually increase as it extends radially outward, for example. An outer corner portion (corner portion in the claim) 33f is formed at the connection between the connecting surface 33e and the outer peripheral surface 33a. A side corner portion 33g is formed at the connection between the connecting surface 33e and the side surface 33d. The arcuate surface 33h smoothly connects the side surface 33d and the inner circumferential surface 33b.

[0039] <Radial length of the first salient pole, and radial length of the second salient pole> Next, the radial lengths of the first salient pole 91 and the second salient pole 92 will be described based on Figures 4 and 5. First, let's explain the radial length of the first salient pole 91. The radial length of the first salient pole 91 is the length such that the radially outer tip 91a of the first salient pole 91 is in the following position.

[0040] In other words, the tip 91a of the first salient pole 91 is located radially outward from the outer corner portion 33f of the permanent magnet 33, and radially inward from the inner surface 22c of the teeth 22. Radially outward from the outer corner portion 33f of the permanent magnet 33 means radially outward from the straight line L2 that passes through two opposing outer corner portions 33f of adjacent permanent magnets 33 in the circumferential direction.

[0041] Next, we will explain the radial length of the second salient pole 92. Figure 5 is an explanatory diagram of the radial length of the second salient pole 92. Figure 5 is a partially enlarged cross-sectional view along the radial direction of the stator 8 and rotor 9. As shown in Figures 4 and 5, the radial length of the second salient pole 92 is such that the radially outer tip 92a of the second salient pole 92 is in the following position: That is, the tip 92a of the second salient pole 92 is located radially outward from the central position 92c between the outer corner portion 33f of the permanent magnet 33 and the base 92b of the second salient pole 92 (salient pole 35), and radially inward from the outer corner portion 33f (see region Ar shown by dot hatching in Figure 5).

[0042] Here, the base 92b of the second salient pole 92 (salient pole 35) refers to the connection point between the rounded chamfered portion 35c of the salient pole 35 and the outer circumferential surface 32b of the rotor core 32. The central position 92c between the outer circumferential corner portion 33f of the permanent magnet 33 and the base 92b of the second salient pole 92 (salient pole 35) refers to the central position between the bases 92b on both sides in the circumferential direction of the second salient pole 92 (salient pole 35) and the intersection point S of the line L3 parallel to the side surface 35a of the salient pole 35 passing through the base 92b and the line L2. Radially inside the outer circumferential corner portion 33f of the permanent magnet 33 refers to radially inside the line L2.

[0043] <Deceleration part> Returning to Figures 1 and 2, the reduction unit 3 comprises a gear case 40 to which the motor case 5 is attached, and a worm reduction mechanism 41 housed within the gear case 40. The gear case 40 is formed from a material with excellent heat dissipation properties, such as die-cast aluminum. The gear case 40 is formed in a box shape with an opening 40a on one side.

[0044] The gear case 40 has a gear housing section 42 that houses a worm reduction mechanism 41 inside. An opening 43 is formed in the side wall 40b of the gear case 40. The opening 43 is formed in a location where the first motor case 6 is integrally molded. The opening 43 allows the through hole 10a of the first motor case 6 to pass through to the gear housing section 42.

[0045] A cylindrical bearing boss 49 is provided protruding from the bottom wall 40c of the gear case 40. The bearing boss 49 is provided to rotatably support the output shaft 48 of the worm reduction mechanism 41. A sliding bearing (not shown) is provided on the inner circumferential surface of the bearing boss 49. An O-ring (not shown) is fitted to the inner circumferential edge of the tip of the bearing boss 49. This prevents dust and water from entering the interior from the outside through the bearing boss 49. Multiple ribs 52 are provided on the outer circumferential surface of the bearing boss 49. This ensures the desired rigidity of the bearing boss 49.

[0046] The worm gear reduction mechanism 41 consists of a worm shaft 44 and a worm wheel 45 that meshes with the worm shaft 44. The worm shaft 44 is positioned coaxially with the shaft 31 of the electric motor 2. The worm shaft 44 is rotatably supported at both ends by bearings 46 and 47 provided in the gear case 40. The end of the worm shaft 44 on the electric motor 2 side protrudes through the bearing 46 to the opening 43 of the gear case 40.

[0047] The end of the protruding worm shaft 44 and the end of the shaft 31 of the electric motor 2 are joined together, so that the worm shaft 44 and the shaft 31 are integrated. However, the invention is not limited to this, and the worm shaft 44 and the shaft 31 may be formed as a single unit by molding the worm shaft portion and the rotating shaft portion from a single base material.

[0048] An output shaft 48 is provided at the radial center of the worm wheel 45. The output shaft 48 is positioned coaxially with the rotation axis of the worm wheel 45. The output shaft 48 protrudes to the outside of the gear case 40 via a bearing boss 49 of the gear case 40. A spline 48a is formed at the protruding tip of the output shaft 48, which can be connected to electrical components (not shown).

[0049] A sensor magnet (not shown) is provided at the radial center of the worm wheel 45, on the side opposite to the side from which the output shaft 48 protrudes. The sensor magnet constitutes one part of the rotational position detection unit 60, which detects the rotational position of the worm wheel 45. The other part of the rotational position detection unit 60, the magnetic detection element 61, is provided in the controller unit 4, which is positioned opposite the worm wheel 45 on the sensor magnet side of the worm wheel 45 (the side of the opening 40a of the gear case 40).

[0050] <Controller section> The controller unit 4 includes a controller board 62 on which a magnetic detection element 61 is mounted, and a cover 63 provided to close the opening 40a of the gear case 40. The controller board 62 is positioned opposite the sensor magnet side of the worm wheel 45 (the side of the opening 40a of the gear case 40).

[0051] The controller board 62 is made of a so-called epoxy substrate with multiple conductive patterns (not shown) formed on it. The terminals of the coils 24 drawn from the stator core 20 of the electric motor 2 are connected to the controller board 62. Terminals (not shown) of a connector 11 provided on the cover 63 are electrically connected to the controller board 62.

[0052] In addition to the magnetic detection element 61, the controller board 62 is equipped with a power module (not shown) which has switching elements such as an FET (Field Effect Transistor) that controls the current supplied to the coil 24. Capacitors and the like are also mounted on the controller board 62. The capacitors and the like smooth the voltage applied to the controller board 62.

[0053] The cover 63 that covers the controller board 62 is made of resin. The cover 63 is formed to bulge slightly outward. The inner surface of the cover 63 is a controller housing section 56 that houses the controller board 62 and the like. A connector 11 is integrally molded on the outer periphery of the cover 63. The connector 11 is formed to be compatible with a connector extending from an external power supply (not shown). A controller board 62 is electrically connected to terminals (not shown) of the connector 11. This supplies power from the external power supply to the controller board 62.

[0054] A fitting portion 81 is formed protruding from the opening edge of the cover 63. The fitting portion 81 is fitted into the end of the side wall 40b of the gear case 40. The fitting portion 81 is composed of two walls 81a and 81b that run along the opening edge of the cover 63. The end of the side wall 40b of the gear case 40 is inserted (fitted) between these two walls 81a and 81b. This forms a labyrinth portion 83 between the gear case 40 and the cover 63. The labyrinth portion 83 prevents dust or water from entering between the gear case 40 and the cover 63. The gear case 40 and the cover 63 are fixed together by fastening bolts (not shown).

[0055] <Operation of a motor with a gearbox> Next, the operation of the motor 1 with a reduction gear will be explained. In the motor 1 with a reduction gear, the power supplied to the controller board 62 via the connector 11 is selectively supplied to each coil 24 of the electric motor 2 via a power module (not shown). The current flowing through each coil 24 then forms a predetermined flux linkage in the stator 8 (teeth 22). This flux linkage generates a magnetic attractive or repulsive force (magnetic torque) between itself and the effective flux formed by the permanent magnets 33 of the rotor 9.

[0056] The salient poles 35 of the rotor core 32 are positioned to allow the flux linkage from the stator 8 (teeth 22) to flow easily, and generate a reluctance torque that rotates the rotor core 32 in order to reduce the magnetic resistance (reluctance) of the flux linkage path. These magnetic torques and reluctance torques cause the rotor 9 to rotate continuously.

[0057] The rotation of the rotor 9 is transmitted to the worm shaft 44, which is integrated with the shaft 31, and further to the worm wheel 45, which is meshed with the worm shaft 44. The rotation of the worm wheel 45 is transmitted to the output shaft 48, which is connected to the worm wheel 45, and the output shaft 48 drives the desired electrical components.

[0058] The detection signal of the rotational position of the worm wheel 45, detected by the magnetic detection element 61 mounted on the controller board 62, is output to an external device (not shown). The external device is, for example, a software function unit that operates when a predetermined program is executed by a processor such as a CPU (Central Processing Unit).

[0059] The software function unit is an ECU (Electronic Control Unit) that includes a processor such as a CPU, ROM (Read Only Memory) for storing programs, RAM (Random Access Memory) for temporarily storing data, and electronic circuits such as timers.

[0060] At least a portion of the external equipment may be an integrated circuit such as an LSI (Large Scale Integration). The external equipment controls the switching timing of switching elements of a power module (not shown) based on the rotational position detection signal of the worm wheel 45, and controls the drive of the electric motor 2. The output of the drive signal of the power module and the drive control of the electric motor 2 may be performed by the controller unit 4 instead of the external equipment.

[0061] <Analysis of the order of torque waveform and torque ripple of the rotor> Next, we will explain the torque waveform of the rotor 9 and the order analysis of the torque ripple of the rotor 9 based on Figures 6 and 7. Figure 6 is a graph showing the change in torque of the rotor 9, with torque on the vertical axis and rotation angle on the horizontal axis. In Figure 6, the torque waveform shown by the solid line is the torque waveform of this embodiment. In Figure 6, the torque waveform shown by the dashed line is a conventional torque waveform shown for comparison. Conventional refers to a rotor 9 in which the radial lengths of all salient poles 35 are the same (the same applies to Figure 7 below). In the conventional design, the tips of the salient poles 35 are assumed to be located on the circumference passing through the central part 33c of the permanent magnet 33.

[0062] As shown in Figure 6, the torque of the rotor 9 is obtained by two torques: magnetic torque and reluctance torque. Here, the reluctance torque pulsates each time the salient pole 35 crosses the teeth 22. In the conventional case (see the dashed line in Figure 6), the radial length of all salient poles 35 is the same, so the amplitude of the reluctance torque waveform is also constant. In contrast, the salient pole 35 in this embodiment is composed of a first salient pole 91 and a second salient pole 92 of different lengths. Therefore, the reluctance torque waveform is one in which large and small amplitudes alternate.

[0063] Figure 7 is a graph comparing the order components of torque ripple and the magnitude of torque ripple for each order component between the rotor 9 of this embodiment and a conventional rotor. As shown in Figure 7, in conventional rotors, the order component of the least common multiple of the number of magnetic poles and the number of slots tended to be significantly large. The least common multiple of the number of magnetic poles and the number of slots referred to here is the same as the least common multiple of the number of magnetic poles and the number of slots in this embodiment. Since the electric motor 2 in this embodiment is composed of 4 poles and 6 slots, in the conventional case, the torque ripple of the 12th order component becomes significantly large.

[0064] In contrast, in the electric motor 2 of this embodiment, although torque ripple of the 6th and 18th order components occurs compared to the conventional model, it can be confirmed that the generation of significantly larger order components is prevented. In other words, it can be confirmed that the overall torque ripple is reduced compared to the conventional model.

[0065] As described above, in the embodiment, the salient pole 35 is composed of a first salient pole 91 and a second salient pole 92 of different lengths. The tip 91a of the first salient pole 91 is located radially outward from the outer corner portion 33f of the permanent magnet 33. The tip 92a of the second salient pole 92 is located radially inward from the outer corner portion 33f of the permanent magnet 33. The first salient pole 91 and the second salient pole 92 are arranged alternately in the circumferential direction. Therefore, it is possible to suppress a significant increase in a specific order component (for example, the 12th order component in this embodiment) of the torque ripple of the rotor 9. As a result, the noise and vibration of the electric motor 2 can be reduced.

[0066] Furthermore, the tip 91a of the first salient pole 91 is located radially outward from the outer corner portion 33f of the permanent magnet 33, and radially inward from the inner surface 22c of the teeth 22. Therefore, the tip 91a of the first salient pole 91 can be brought as close as possible to the teeth 22. As a result, the torque due to reluctance torque can be increased, and the reluctance ripple can be increased. Thus, the noise and vibration of the electric motor 2 can be reliably reduced while suppressing a reduction in the motor torque performance of the electric motor 2.

[0067] The tip 92a of the second salient pole 92 is located radially outward from the central position 92c between the outer corner portion 33f of the permanent magnet 33 and the base 92b of the second salient pole 92 (salient pole 35), and radially inward from the outer corner portion 33f. Therefore, even when the tip 92a of the second salient pole 92 is positioned radially inward from the outer corner portion 33f of the permanent magnet 33, the reduction in the amount of flux linkage of the stator 8 flowing into the second salient pole 92 can be minimized. Thus, the noise and vibration of the electric motor 2 can be reliably reduced while suppressing a reduction in the motor torque performance of the electric motor 2.

[0068] The permanent magnet 33 has a misalignment between the position of the arc center Co on the outer surface 33a and the position of the arc center Ci on the inner surface 33b. That is, the arc centers Co and Ci are located on a straight line L1 passing through the axis of rotation C1 and the circumferential central part 33c of the permanent magnet 33, and the arc center Co of the outer surface 33a is located radially outward from the arc center Ci of the inner surface 33b. As a result, the radial thickness of the permanent magnet 33 gradually increases from both sides in the circumferential direction toward the central part 33c.

[0069] As a result, even when the tip 91a of the first salient pole 91 is positioned radially outward from the outer corner portion 33f of the permanent magnet 33, the clearance between the permanent magnet 33 and the teeth 22 can be made as small as possible. Therefore, the noise and vibration of the electric motor 2 can be reliably reduced while suppressing a reduction in the motor torque performance of the electric motor 2.

[0070] By suppressing a reduction in the motor torque performance of electric motor 2 while reliably reducing the noise and vibration of electric motor 2, it becomes possible to contribute to United Nations Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable, and modern energy for all," and Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0071] The present invention is not limited to the embodiments described above, but includes various modifications to the embodiments described above, without departing from the spirit of the invention. For example, in the above embodiment, the motor with a reduction gear 1 was described in the case where it is used as a drive source for a vehicle's wiper device. However, it is not limited to this, and the motor with a reduction gear 1 can be applied to various drive devices. Furthermore, only the electric motor 2 with the above configuration may be used in various electrical devices.

[0072] In the above-described embodiment, an electric motor 2 was used as an example of a rotating electric machine. However, the above configuration can be applied to various rotating electric machines. For example, a generator may be used instead of the electric motor 2 as the rotating electric machine. In the above-described embodiment, the electric motor 2 was described as having 4 magnetic poles for the permanent magnet 33 and 6 slots 19 (teeth 22), and was configured as 4 poles and 6 slots. Correspondingly, the case where there are 4 salient poles 35 was described. However, it is not limited to this, and the number of poles of the electric motor 2 and the number of salient poles 35 can be set arbitrarily.

[0073] In the above-described embodiment, the case was explained in which the tip 91a of the first salient pole 91 is located radially outward from the outer circumferential corner portion 33f of the permanent magnet 33 and radially inward from the inner circumferential surface 22c of the teeth 22. The case was explained in which the tip 92a of the second salient pole 92 is located radially outward from the central position 92c between the outer circumferential corner portion 33f of the permanent magnet 33 and the base 92b of the second salient pole 92 (salient pole 35) and radially inward from the outer circumferential corner portion 33f. However, the embodiment is not limited to this, and the tip 91a of the first salient pole 91 only needs to be located radially outward from the outer circumferential corner portion 33f of the permanent magnet 33. The tip 92a of the second salient pole 92 only needs to be located radially inward from the outer circumferential corner portion 33f of the permanent magnet 33.

[0074] In the above-described embodiment, the case where the position of the arc center Co on the outer circumferential surface 33a and the position of the arc center Ci on the inner circumferential surface 33b are misaligned was explained. This described a case where the radial thickness of the permanent magnet 33 gradually increases from both sides in the circumferential direction toward the central part 33c. However, it is not limited to this, and the position of the arc center Co on the outer circumferential surface 33a and the position of the arc center Ci on the inner circumferential surface 33b may be the same. Each arc center Co,Ci may be located on the axis of rotation C1. In this case, the radial thickness of the permanent magnet 33 may be uniform throughout the entire circumferential direction. [Explanation of Symbols]

[0075] 1…Motor with reduction gear, 2…Electric motor (rotating electric machine), 3…Reduction unit, 4…Controller unit, 5…Motor case, 6…First motor case, 6a…Opening, 7…Second motor case, 7a…Opening, 8…Stator, 9…Rotor, 10…Bottom, 10a…Through hole, 11…Connector, 16…Outer flange, 17…Outer flange, 19…Slot, 20…Stator core, 21…Core unit, 22…Tee 22a...Tooth body, 22b...Flange, 22c...Inner surface (inner surface of stator core), 23...Insulator, 24...Coil, 31...Shaft, 32...Rotor core, 32a...Through hole, 32b...Outer surface, 32c...Center, 33...Permanent magnet, 33a...Outer surface, 33b...Inner surface, 33c...Center (circumferential center), 33d...Side, 33e...Connecting surface, 33f...Outer corner (corner), 33g...Side Corner section, 33h...Arch surface, 35...Sailing pole, 35a...Side surface, 35b...Flat surface, 35c...Rounded chamfer, 36...Magnet housing, 40...Gear case, 40a...Opening, 40b...Side wall, 40c...Bottom wall, 41...Worm reduction mechanism, 42...Gear housing, 43...Opening, 44...Worm shaft, 45...Worm wheel, 46...Bearing, 47...Bearing, 48...Output shaft, 48a...Spline, 49...Bearing boss, 52 …rib, 56…controller housing, 60…rotation position detection unit, 61…magnetic detection element, 62…controller board, 63…cover, 81…fitting part, 81a…wall, 81b…wall, 83…labyrinth part, 91…first salient pole, 91a…tip, 92…second salient pole, 92a…tip, 92b…base, 92c…center position, Ar…region, C1…rotation axis, Ci…arc center, Co…arc center, L1…straight line, L2…straight line

Claims

1. A stator core having multiple teeth around which a coil is wound, A rotor is provided radially inward from the aforementioned multiple teeth, and is rotatable around the axis of rotation, Equipped with, The rotor is A shaft that rotates around the aforementioned axis of rotation, A rotor core is fixed coaxially to the aforementioned shaft, Multiple permanent magnets arranged on the outer surface of the rotor core, A plurality of salient poles are provided on the outer circumferential surface of the rotor core, and protrude radially outward from the outer circumferential surface, Equipped with, The plurality of salient poles are arranged between adjacent permanent magnets in the circumferential direction on the outer surface of the rotor core. The surfaces of the plurality of salient poles that face the permanent magnet in the circumferential direction are parallel to the surfaces of the permanent magnet that face the plurality of salient poles in the circumferential direction. The aforementioned multiple salient poles are A first salient pole whose radially outer tip is located radially outward from the corners on both sides of the circumferential surface of the permanent magnet, A second salient pole whose radially outer tip is located radially inward from the corner portion of the permanent magnet, It has, The first salient pole and the second salient pole are arranged alternately in the circumferential direction. A rotating electric machine characterized by the following features.

2. The torque ripple of the rotor has an order component of the least common multiple of the number of magnetic poles of the permanent magnets and the number of slots formed between adjacent teeth in the circumferential direction that is lower than the order component of the torque ripple in a rotor where the position of the radially outer tip of the first salient pole and the position of the radially outer tip of the second salient pole are the same. The rotating electric machine according to feature 1.

3. The tip of the first salient pole is located radially outward from the corner of the permanent magnet and radially inward from the inner circumferential surface of the stator core. The rotating electric machine according to claim 1 or 2.

4. The rotating electric machine according to claim 1 or 2, characterized in that the tip of the second salient pole is located radially outward from the central position between the corner of the permanent magnet and the base of the salient pole, and radially inward from the corner of the permanent magnet.

5. The permanent magnet has a connecting surface that is connected to the side surface and the outer peripheral surface, The aforementioned connecting surface is a flat surface formed by a planar cut. The aforementioned corner portion is located at the connection point between the connecting surface and the outer peripheral surface. A side corner is formed at the connection between the connecting surface and the side surface. The tip of the second salient pole is located radially outward from the side corner. The rotating electric machine according to claim 1 or 2.

6. The arc centers of the inner surface and outer surface of the permanent magnet are located on a straight line passing through the axis of rotation and the circumferential center of the permanent magnet. The center of the arc on the outer surface of the permanent magnet is located radially outward with respect to the center of the arc on the inner surface. The rotating electric machine according to claim 1 or 2.

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