JP2013215028A - Single-phase induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce torque ripples generated at stator teeth and rotor teeth when a rotor of a single-phase induction motor rotates.SOLUTION: A single-phase induction motor comprises: a stator including an annular core back 211, a plurality of stator teeth 212, and a plurality of coils; and a rotor core including a back yoke 321, and a plurality of rotor teeth 322. The plurality of rotor teeth 322 are extended outward from the back yoke 321 in a radial direction and arranged at equal intervals in a circumferential direction. When the number of pairs of a plurality of magnetic poles, S and N, which are distributed in the stator, is regarded as the number of pole pairs, the number of rotor teeth 322 and the number of pole pairs satisfy any one of the following formulas: (the number of rotor teeth 322)=(the number of magnetic poles)×(2n-1); or when the number of magnetic poles is not less than 6, (the number of rotor teeth 322)=(the number of magnetic poles)×(2n-1)+1, or (the number of rotor teeth 322)=(the number of magnetic poles)×(2n-1)-1, where n is a natural number not including 0.

Description

  The present invention relates to an inner rotor type single-phase induction motor.

  With the advancement of technology, the demand for value-added performance such as low vibration and low noise is increasing in recent home appliances. An AC induction motor is often used to drive home appliances. A motor as a driving body is a main cause of vibration and noise of home appliances.

The AC induction motor includes a stator and a rotor. When the stator is excited, torque is generated with respect to the rotor, and the rotor rotates. The fluctuation of the generated torque is called torque ripple. The fluctuation range of this torque ripple is related to vibration and noise.
Japanese Patent Application Laid-Open No. 2010-130839 discloses an induction motor that reduces vibration and noise by setting the relationship between the thickness of the flange portion and the thickness of the flange portion of the stator teeth.
Japanese Patent Laid-Open No. 2002-369469 discloses an induction motor that reduces vibration and noise by skewing teeth.
In the above document, the torque fluctuation range is reduced by reducing the torque. That is, the fluctuation range of the torque cannot be reduced while maintaining the magnitude of the torque. Therefore, a method for further reducing vibration while maintaining the torque has been demanded.
JP 2010-130839 A JP 2002-369469 A

  Up to now, the single-phase induction motor that has been devised has sacrificed torque and reduced the fluctuation range of torque ripple. Therefore, in a single-phase induction motor, there is a need for a technique for reducing the combined torque ripple by combining the torque generated in each of the stator teeth and the rotor teeth generated when the rotor rotates as a torque ripple.

  A rotating portion including a shaft and a rotor core; a stationary portion including a stator; and a bearing portion that supports the rotating portion so as to be rotatable about a central axis with respect to the stationary portion, the stator including a magnetic plate An annular core back, a plurality of stator teeth extending radially inward from the core back, and a plurality of coils mounted on each of the plurality of stator teeth in a concentrated winding manner. The plurality of coils includes a plurality of main coils formed by main windings in which continuous windings are wound around every other stator tooth while reversing the winding direction. A plurality of auxiliary coils formed by auxiliary windings wound around stator teeth positioned between every other stator teeth while reversing the winding direction, and the rotor core comprises: And a plurality of rotor teeth, the plurality of rotor teeth extending radially outward from the back yoke and arranged at equal intervals in the circumferential direction, and S of a plurality of magnetic poles distributed in the stator A single-phase induction motor in which the number of rotor teeth and the number of pole pairs satisfy one of the following relational expressions, where the number of pairs of N and N is the number of pole pairs. (Number of rotor teeth) = (Number of magnetic poles) × (2n−1), When the number of magnetic poles is 6 or more, (Number of rotor teeth) = (Number of magnetic poles) × (2n−1) +1 or rotor Number of teeth) = (Number of magnetic poles) × (2n−1) −1 However, n is a natural number not including 0.

  In the single-phase induction motor according to the present invention, vibration and noise are suppressed when the number of magnetic poles and the number of rotor teeth satisfy any of the above relational expressions.

FIG. 1 is a longitudinal sectional view of a single-phase induction motor according to an embodiment. FIG. 2 is a perspective view of the rotating unit. FIG. 3 is a plan view of the rotor core. FIG. 4 is a plan view of the stator in the unfolded state. FIG. 5 is an enlarged view of the core element. FIG. 6 is an enlarged view of the vicinity of the connecting portion. FIG. 7 is a plan view of the stator. FIG. 8 is a schematic diagram of the magnetic path distribution when there are 8 stator teeth and 14 rotor teeth. FIG. 9 is a schematic diagram of the magnetic path distribution when there are 12 stator teeth and 21 rotor teeth. FIG. 10 is a schematic diagram of the magnetic path distribution when there are 12 stator teeth and 22 rotor teeth. FIG. 11 is a diagram illustrating the relationship between the number of magnetic poles and the rotor teeth.

  In the present specification, the upper side in the direction of the central axis J1 of the motor 1 shown in FIG. 1 is simply referred to as “upper side”, and the lower side is simply referred to as “lower side”. Note that the vertical direction does not indicate the positional relationship or direction when incorporated in an actual device. A direction parallel to the central axis J1 is referred to as an “axial direction”, a radial direction centered on the central axis is simply referred to as “radial direction”, and a circumferential direction centered on the central axis is simply referred to as “circumferential direction”. .

  FIG. 1 is a longitudinal sectional view showing a single-phase induction motor 1 (hereinafter referred to as “motor 1”) according to an exemplary embodiment of the present invention. The motor 1 is preferably used for a fan, a blower, an air cleaner, or an air conditioner. The motor 1 is an inner rotor type. When the single-phase alternating current is input, the rotating unit 3 of the motor 1 rotates. The motor 1 includes a stationary part 2, a rotating part 3, and a bearing part 4. The bearing portion 4 supports the rotating portion 3 so as to be rotatable with respect to the stationary portion 2 around the central axis J1. The bearing portion 4 includes a first ball bearing 41 and a second ball bearing 42. The second ball bearing 42 is disposed on the upper side in the axial direction of the rotating unit 3, and the first ball bearing 41 is disposed on the lower side in the axial direction of the rotating unit 3.

  The stationary part 2 includes a stator 21 and a housing 22. The stator 21 is disposed on the outer side in the radial direction of the rotor core 32 described later. The stator 21 includes an annular core back 211, a plurality of stator teeth 212, and a plurality of coils 213. The plurality of stator teeth 212 extends from the inner peripheral surface of the core back 211 toward the central axis J1. The coil 213 is attached to each of the plurality of stator teeth 212 in the form of concentrated winding. The types of winding are roughly classified into concentrated winding and distributed winding. In contrast to the distributed winding in which the conducting wire is wound across the plurality of stator teeth, the concentrated winding forms the coil 213 by winding the conducting wire intensively around one stator tooth. The plurality of coils 213 includes a plurality of main coils 214 and a plurality of auxiliary coils 215. The coil in which the forward winding and the reverse winding are alternately arranged with respect to every other stator tooth 212 having a continuous conducting wire is a main coil 214. For every other stator tooth 212 positioned between the stator teeth 212 around which the main coil 214 is wound, a coil in which continuous conducting wires are alternately arranged in forward and reverse turns is used as an auxiliary. Coil 215. When the main coil 214 starts to be wound in the forward rotation, the start of the auxiliary coil 215 wound around the adjacent stator teeth 212 is the reverse rotation. Different conductors are used for the main coil 214 and the auxiliary coil 215. That is, the plurality of coils 213 are configured by two continuous conductors.

  Similar to a normal single-phase induction motor, the motor 1 includes a capacitor. The phase of the alternating current flowing through the main coil 214 by the capacitor is 90 ° out of phase with the alternating current flowing through the auxiliary winding. As a result, a rotating magnetic field is generated inside the stator 21 and the rotating portion 3 rotates.

  The housing 22 includes an upper housing 221 and a lower housing 222. The upper housing 221 and the lower housing 222 face each other in the axial direction and are fixed by fitting. The housing 22 covers the stator 21 over the entire circumference. The upper housing 221 includes a first bearing holding portion 2211. The first bearing holding portion 2211 is a cylindrical portion that is arranged coaxially with the central axis J <b> 1 and extends in the axial direction from the lid portion of the upper housing 221. The first ball bearing 41 is held by the first bearing holding portion 2211. The lower housing 222 includes a second bearing holding portion 2221. The second bearing holding portion 2221 is a cylindrical portion that is disposed coaxially with the central axis J <b> 1 and extends in the axial direction from the bottom of the lower housing 222. The second ball bearing 42 is held by the second bearing holding portion 2212.

    FIG. 2 is a perspective view of the rotating unit 3. The rotating unit 3 includes a shaft 31, a rotor core 32, and an end ring 33. The shaft 31 is supported by the first ball bearing 41 and the second ball bearing 42 so as to be rotatable about the central axis J1. The output end of the shaft 31 protrudes downward from the opening of the second bearing holding portion 2212. The rotor core 32 is a laminate formed by laminating laminations that are magnetic plates. The rotor core 32 is disposed inside the stator 21 in the radial direction. The end rings 33 are annularly provided on the upper and lower surfaces of the rotor core 32. Each lamination constituting the rotor core 32 includes a plurality of rotor teeth 322. The plurality of rotor teeth 322 extend radially outward from the annular back yoke 321 and are arranged at equal intervals in the circumferential direction. The plurality of rotor teeth 322 have a rotor umbrella portion 323 extending in the circumferential direction at the radially outer end. The umbrella parts of the adjacent rotor teeth 322 face each other in the circumferential direction, and have a rotor slot open 324 therebetween. Between the plurality of rotor teeth 322, there are a plurality of gaps 325 from the rotor slot opening 324 to the back yoke 321.

  FIG. 3 is a plan view of the rotor core. As shown in FIG. 3, the plurality of laminations are laminated in a state where the rotor slot open 324 is out of phase by a predetermined angle in the circumferential direction, thereby forming the rotor core 32. That is, the rotor core 32 is configured by laminating laminations in a skewed state. A case where the lower end 321a of the gap 325 is disposed directly below the upper end 321b of the adjacent gap 325 in the axial direction is 1.0 skew.

  An end ring 33 formed of aluminum or an aluminum alloy is integrally formed on the rotor core 32 by insert molding in aluminum die casting. The end ring 33 includes two rings 331 positioned above and below the rotor core 32 and a plurality of columns 332 that connect the two rings 331 in the axial direction. One of the plurality of pillars 332 is located in each gap 325 of the lamination. Since the end ring 33 is molded by die casting, the gap 325 is filled with aluminum or an aluminum alloy as a material of the column 332. That is, since the rotor core 32 and the end ring 33 are configured in close contact with each other, they have high rigidity. A squirrel-cage rotor is formed by connecting the end ring 33 to the metal filled in the rotor core 32.

  FIG. 4 is a plan view of the stator 21 in the unfolded state. The left direction in FIG. 4 is the radially outward direction, and the upward direction is the circumferential direction. The stator 21 is a set group of a plurality of cores 60. Each of the plurality of cores 60 includes one tooth portion 61 and a core back portion 621. The core back part 621 is a 1/8 part of the core back 211. The plurality of core back portions 621 are arranged approximately in a straight line. The teeth portion 61 extends from each core back portion 621 in a direction perpendicular to the core back portion 621. Furthermore, the tooth part 61 has a stator umbrella part 622 extending in the vertical direction of the tooth part 61 at the tip. The stator umbrella portion 622 is curved in a direction away from the core back portion 621 as it is away from the tooth portion 61. That is, the tip of the umbrella part 622 has an arc shape.

  The core back portions 621 adjacent to each other are connected by a minute connecting portion 623. The stator 21 shown in FIG. 4 is bent at the connecting portion 623, whereby the annular stator 21 is formed. The core back portions 621 at both ends in FIG. 4 are joined by welding. When the stator 21 is annular, the connecting portion 623 is positioned on the outer side in the radial direction and on both sides in the circumferential direction (however, only one of the core back portions 621 of the core 60 located at the end). There is a gap between the umbrella element 622 and the adjacent stator umbrella portion 622. This gap is referred to as status lot open 624. A plurality of stator umbrella portions 622 and status lot open 624 form a virtual circle. The diameter of this virtual circle is the stator inner diameter 70. The outer diameter of the annular core back 211 is the stator outer diameter 80.

  FIG. 5 is an enlarged view of the core 60. Hereinafter, the lower side in FIG. 5 is defined as the radially inner side, and the upper side is defined as the radially outer side. The left and right sides of the core back portion 621 in FIG. 6, that is, the side surfaces 651 facing the adjacent core back portion 621 are located on the radially inner side of the connecting portion 622. By making the stator 21 annular, the mutually opposing side surfaces 651 of the adjacent core back portions 621 substantially contact each other. Hereinafter, the side surface 651 is referred to as “mating surface”. The mating surface 651 is a flat surface. When the mating surfaces 651 come into contact with each other, a magnetic path in the core back 211 is formed. In the following description, the outer side in the radial direction of the core back part 621, that is, the surface 653 opposite to the teeth part 61 is referred to as “outer surface”, and the inner side in the radial direction, that is, the surface 654 on the teeth part 61 side is referred to as “inner surface”. That's it.

  FIG. 6 is an enlarged view of the vicinity of the connecting portion 622. The outer surface 653 of the core back part 621 is a substantially flat surface, but slightly toward the teeth part 61 in the vicinity of the connecting part 622. A radially inner surface of the connecting portion 622 is a micro cylindrical surface 652 (more precisely, a part of the micro cylindrical surface) extending in the thickness direction of the stator 21. The mating surface 651 extends from the minute cylindrical surface 652 toward the teeth portion 61 side. The micro cylindrical surface 652 and the mating surface 651 are smoothly connected. When the stator 21 is annular and the mating surfaces 651 overlap each other, the mating surface 651 extends in the radial direction.

  The outer surface 653 of the core back portion 621 is preferably 70% or more flat in the circumferential direction, that is, in the left-right direction in the unfolded state shown in FIG. Thereby, compared with the case where the whole is cylindrical surface shape, more magnetic plate components which comprise the stator 21 can be obtained from the same amount of magnetic plates. The plane of the outer surface 653 is preferably perpendicular to the direction in which the tooth portion 61 extends. In the core back portion 621, the inner surface 654 is a flat surface extending on both sides in the circumferential direction of the tooth portion 61. Thereby, the magnetic plate component which comprises the stator 21 can be obtained still more efficiently. The entire inner surface 654 does not need to be a flat surface, and the inner surface 654 may include a flat surface extending on both sides in the circumferential direction of the tooth portion 61 and other surfaces.

  As long as the outer surface 653 includes a plane extending substantially perpendicular to the radial direction, the plane does not necessarily have to be exactly perpendicular to the extending direction of the tooth portion 61. The outer surface 653 may not include a flat surface. A part of the outer surface 653 (particularly, the portion opposite to the tooth portion 61) may be a cylindrical surface centered on the central axis J1. A circumscribed circle of the stator 21, that is, a part of the outer surface 653 with respect to the outer diameter of the core back 211 is located on the inner side in the radial direction.

  On both sides of the tooth portion 61, the radial minimum width W <b> 1 of the core back portion 621 is equal to or greater than the circumferential minimum width W <b> 2 of the tooth portion 61. Here, the width in the radial direction of the core back portion 621 indicates the width in the substantially radial direction of the core back portion 621, and indicates the distance from one point on the outer surface 653 to one point on the shortest inner surface 654. . Moreover, the minimum width in the radial direction of the core back portion 621 means the minimum width at a portion not including the mating surface 651. The minimum width in the circumferential direction of the teeth 61 indicates the minimum width in a direction perpendicular to the central axis J1 of the stator 21 and the central axis of the teeth 61.

  In the case of a concentrated winding single-phase induction motor, the maximum magnetic flux flowing through the stator teeth 212 and the maximum magnetic flux flowing through the core back 211 are theoretically equal. Therefore, if the minimum width of the core back 211 is made smaller than the minimum width of the stator teeth 212, the magnetic flux may leak from the core back 211. Alternatively, the stator teeth 212 become thicker than necessary with respect to the core back 211, and in the case of the inner rotor type, the stator 21 is enlarged in order to secure a space for disposing the stator teeth 212. On the other hand, in the stator 21 of FIG. 6, the minimum core back width W1 is equal to or greater than the minimum teeth width W2.

  The above relationship between the core back minimum width W1 and the teeth minimum width W2 holds when the thickness of the stator 21 is constant. When the thickness of the stator 21 is not constant, the minimum cross-sectional area of the core back part 621 is greater than or equal to the minimum cross-sectional area of the tooth part 61, so that the magnetic flux is prevented from leaking from the core back 211 (magnetic flux leakage). This also applies to the following. Thereby, the fall of the operation efficiency of the motor 1 can be prevented. The minimum cross-sectional area of the core back part 621 is precisely the minimum cross-sectional area of the core back part 621 formed by an arbitrary plane parallel to the axial direction at both sides of the tooth part 61 of the core back part 621. Of course, the cross section intersecting with the mating surface 651 is excluded. In other words, it refers to the smallest cross section that intersects both the outer surface 653 and the inner surface 654 and is parallel to the axial direction. In addition, the minimum cross-sectional area of the tooth portion 61 is precisely the minimum cross-sectional area of an arbitrary surface parallel to the axial direction and intersecting the side surfaces on both sides in the circumferential direction of the tooth portion 61. Usually, it is the area of the cross section perpendicular to the radial direction of the part where the winding is performed.

  The core back 211 includes a stator groove 655 extending in the axial direction on the outer surface 653. The stator groove 655 is used for positioning the stator 21 when the coil 213 is formed by the winding machine. The shortest distance between the inner surface 654, which is a surface extending on both sides of the tooth portion 61 of the core back portion 621, and the stator groove 655 is equal to or greater than W3 and the minimum circumferential width W2 of the tooth portion 61. Thereby, the leakage of magnetic flux can be prevented also between the teeth part 61 and the core back part 621, and the fall of the operating efficiency of the motor 1 can be prevented. The above relationship between the shortest distance W3 and the minimum tooth width W2 is the case where the thickness of the stator 21 is constant. When the thickness of the stator 21 is not constant, the minimum cross-sectional area of the core back part 621 intersecting with the stator groove 655 is equal to or larger than the above-described minimum cross-sectional area of the tooth part 61, thereby preventing magnetic flux leakage. Thereby, the fall of the operation efficiency of the motor 1 is prevented. Note that the minimum cross-sectional area of the core back portion 621 indicates the minimum cross-sectional area of the core back portion 621 at any cross section that is parallel to the axial direction and intersects the stator groove 655 and the inner surface 654.

  In the stator 21, the length of the mating surface 651 in plan view is larger than the circumferential width W <b> 2 of the teeth portion 61. The range of the mating surface 651 is a range that substantially contacts when the stator 21 is annular. If the mating surface 651 is inclined with respect to the radial direction when the stator 21 is annular, the length of the mating surface 651 is the surface extending in the radial direction passing through the center of the mating surface 651 and the central axis J1. The length when 651 is projected shall be pointed out. In the core back part 621, leakage of magnetic flux at the position of the mating surface 651 can be suppressed by setting the length of the mating surface 651 to be equal to or greater than the teeth minimum width W2.

  The above relationship between the length of the mating surface 651 and the minimum tooth width W2 is also the case where the thickness of the stator 21 is constant. When the thickness of the stator 21 is not constant, the area of the mating surface 651 is equal to or larger than the above-described minimum cross-sectional area of the tooth portion 61, so that leakage of magnetic flux is suppressed. If the mating surface 651 is inclined with respect to the radial direction when the stator 21 is annular, the area of the mating surface 651 is the mating surface that extends in the radial direction passing through the center of the mating surface 651 and the central axis J1. The area when 651 is projected shall be pointed out. In addition, when the core back part 621 is linear, the minimum cross-sectional area of the core back part 621 may be larger or smaller than the area of the mating surface 651. In particular, unlike FIG. 6, when the inner surface 654 is a part of a cylindrical surface centered on the central axis J <b> 1, the minimum cross-sectional area of the core back portion 621 is likely to be smaller than the area of the mating surface 651.

  FIG. 7 is a plan view of the stator. It is desirable that the stator inner diameter 70 be a value less than half of the stator outer diameter 80. In particular, the torque can be improved by setting the relationship between the stator inner diameter 70 and the stator outer diameter 80 to be stator inner diameter = stator outer diameter / 2 × (0.88 to 0.99). Further, it is desirable that the value of the diameter of the rotor core 32 is a value of the stator outer diameter × 0.47 or more.

  As the rotor core 32 is made smaller, the surface area of the stator 21 becomes relatively larger, so that the amount of magnetic flux from the stator 21 increases. On the other hand, if the diameter of the rotor core 32 is too small, the secondary resistance of the conductor of the rotor core 32 increases. Therefore, the rotor core 32 does not rotate efficiently.

  FIG. 8 is a schematic view showing a magnetic path loop when there are 8 stator teeth 212 and 14 rotor teeth 322. A magnetic path loop at an arbitrary time of the rotating rotor core 32 is indicated by an arrow. The plurality of coils 213 are indicated by dotted lines. Depending on the coil winding method described above, the main coil 214 and one of the auxiliary coils 215a adjacent to the main coil 214 have the same winding direction. Therefore, when a current flows through the main coil 214 and the auxiliary coil 215a, the main coil 214 and the auxiliary coil 215a become the same magnetic pole. That is, the main coil 214 and the auxiliary coil 215a constitute one magnetic pole. The main coil 214 and the other auxiliary coil 215b adjacent to the main coil 214 create one magnetic path loop. At this time, the number of magnetic poles refers to the number of magnetic poles distributed in the stator 21. Therefore, in FIG. 8, the number of magnetic poles is four. The number of magnetic path loops is four. The number of pole pairs indicates the number of pairs of magnetic poles S and N. Therefore, the number of pole pairs is two.

  The magnetic path loop is a closed loop through which the magnetic flux passes through the first stator teeth 2121 → the first rotor teeth 3221 → the back yoke 321 → the second rotor teeth 3222 → the second stator teeth 2122 → the core back 211. For convenience of explanation, the stator teeth 212 and the rotor teeth 322 related to the flow of magnetic flux from the stator 21 to the rotor core 32 are referred to as a first stator tooth 2121 and a first rotor tooth 3221. The stator teeth 212 and the rotor teeth 322 related to the flow of magnetic flux from the rotor core 32 to the stator 21 are referred to as second stator teeth 2122 and second rotor teeth 3222.

  The magnetic path 1 connects the center of the first rotor teeth 3221 from the center of the first stator teeth 2121 and is indicated by a solid line. The magnetic path 2 connects the center 3211 of the gap 325 from the center of the first stator teeth 2121 and is indicated by a dotted line. When attention is paid to one magnetic path loop, the rotor teeth 322 are located on the radially inner side of the first stator teeth 2121 and the second stator teeth 2122. At this time, the rotor teeth 322 located on the radially inner side of the first stator teeth 2121 and the rotor teeth 322 located on the radially inner side of the second stator teeth 2122 have different circumferential positions. That is, the flow of magnetic flux generated when a current is passed through the main coil 214 and the auxiliary coil 215 is arranged on the inner side in the radial direction of the rotor teeth 322 and the second stator teeth 2122 on the inner side in the radial direction of the first stator teeth 2121. The way the magnetic flux flows differs between the rotor teeth 322 positioned. The magnetic path 1 and the magnetic path 2 have different ways of flowing magnetic flux. When FIG. 7 is seen, the magnetic path 1 which becomes the same magnetic path loop appears in the position of 180 degree | times centering on the central axis J1, and the magnetic path 2 is similarly in the position of 180 degree | times centering on the central axis J1. appear.

  When the rotor core 32 rotates, torque is generated for each stator tooth 212. This torque variation is called torque ripple. The synthesized torque ripple refers to a synthesized torque ripple generated in each of the stator teeth 212. In the case of the embodiment of FIG. 7, the same magnetic path loop appears every 180 degrees around the central axis J1. Since the same magnetic path loop appears at a position of 180 degrees with the central axis J1 as the center, partial magnetic force bias does not occur. On the other hand, when the way of connecting the magnetic path loops is different over the entire circumference, the magnetic force is partially biased, so that radial vibration occurs. Further, since the torque ripple generated in each stator tooth 212 is different, the synthesized torque ripple is also increased. That is, the vibration in the radial direction can be reduced by appearing each time the magnetic path loop rotates 180 degrees and canceling out the mutual torque ripples.

  Moreover, the magnetic path 1 and the magnetic path 2 appear every 90 degrees centering on the central axis J1. This means that a plurality of magnetic path loops are generated when the torque ripples cancel each other. On the other hand, there is a condition for canceling each other's torque ripple by one type of magnetic path loop. However, in this case, the torque generated in the stator teeth 212 may increase. As a result, when the torque ripples cancel each other and when the torque ripples do not cancel each other, the fluctuation range of the torque generated in the stator teeth 212 becomes large. As a result, the pulsation of the synthesized torque ripple increases. The pulsation of the synthesized torque ripple causes uneven rotation speed of the rotor core 32 and causes vibration and noise. When a plurality of magnetic path loops are generated under the condition that the torque ripples cancel each other, the fluctuation range of the torque generated in the stator teeth 212 becomes small.

  In order to reduce the synthesized torque ripple, it is necessary to have a condition for canceling each other's torque ripple and a condition for reducing the torque fluctuation range. In other words, in order to reduce the synthesized torque ripple, it is necessary to form a plurality of magnetic path loops when canceling each other's torque ripple. As a result, it is possible to reduce radial vibration due to magnetic force bias during rotation and vibration due to the pulsation of the synthesized torque ripple.

  FIG. 9 is a schematic diagram showing a loop of a magnetic path when there are 12 stator teeth 212 and 21 rotor teeth 322. The number of magnetic poles is 6, and the number of pole pairs is 3. At this time, there are two types of similar magnetic path loops. The magnetic path 1 is indicated by a solid line, and the magnetic path 2 is indicated by a dotted line. The magnetic path 1 connects the center of the first rotor teeth 3221 from the center of the first stator teeth 2121. The magnetic path 2 connects the center 3211 of the gap 325 from the center of the first stator teeth 2121. The magnetic path 1 and the magnetic path 2 are arranged in order counterclockwise. That is, the magnetic path 1 and the magnetic path 2 are positioned at an equal distribution of 120 degrees with the central axis J1 as the center. Even in this case, the torque ripples cancel each other. Therefore, there is no bias in the magnetic force of the rotating magnetic flux over the entire circumference. In addition, since a plurality of magnetic path loops are generated, the fluctuation range of the torque generated in the stator teeth 212 becomes small.

  FIG. 10 is a schematic diagram showing a loop of the magnetic path when there are 12 stator teeth 212 and 22 rotor teeth 322. The number of magnetic poles is 6, and the number of pole pairs is 3. At this time, there are three types of similar magnetic path loops. The magnetic path 1 is indicated by a solid line, the magnetic path 2 is indicated by a dotted line, and the magnetic path 3 is indicated by a one-dot chain line. The magnetic path 1 connects the center of the first rotor teeth 3221 from the center of the first stator teeth 2121. The magnetic path 2 connects the center 3211 of the second stator teeth 2122 from the center 3211 of the gap 325. The magnetic path 3 connects a position shifted from the center of the first rotor teeth 3221 from the center of the first stator teeth 2121. At this time, the magnetic path 1, the magnetic path 2, and the magnetic path 3 are arranged in order counterclockwise. The magnetic path 1, the magnetic path 2, and the magnetic path 3 are positioned at an equal distribution of 180 degrees with the central axis J1 as the center. Therefore, there is no bias in the magnetic force of the rotating magnetic flux. Therefore, vibration and noise can be reduced when the motor is driven.

  When the number of pole pairs is 2, the magnetic paths connecting the same loops are positioned at an equal distribution of 180 degrees with the central axis J1 as the center. When the number of pole pairs is 3, the distribution of loops connecting the same magnetic path is divided into 120 degree equidistant and 180 degree equidistant centered on the central axis J1. The 180 degree equidistant centering on the central axis J1 has a smaller torque fluctuation range than the 120 degree equidistant centering on the central axis J1. This is because there are three types of magnetic path loop connection methods when canceling each other's torque ripple. As a result, vibration and noise can be further reduced.

  FIG. 11 summarizes the number of magnetic poles with which the synthesized torque ripple is reduced and the number of rotor teeth 322 in a table.

In order to reduce the combined torque ripple as described above, the conditions for canceling each other's torque ripple and the conditions for reducing the torque fluctuation range satisfy either of the following relational expressions.
(Number of rotor teeth) = (Number of pole pairs) × (2n−1) (Formula 1)
When the number of magnetic poles is 6 or more, (number of rotor teeth) = (number of pole pairs) × (2n−1) +1 (Expression 2)
When the number of magnetic poles is 6 or more, (number of rotor teeth) = (number of pole pairs) × (2n−1) −1 (Equation 3)
However, n is a natural number not including 0.

  Further, as the number of stator teeth 212 increases, the leakage magnetic flux from stator teeth 212 decreases. Therefore, the disturbance of the induced voltage waveform is reduced, leading to improvement in motor efficiency.

  In the present embodiment, when the number of stator teeth 212 is 8, the skew of the rotor core 32 is 0.6 to 1.2. That is, the angle formed by the central axis J1 and the rotor teeth 322 is preferably about 15 degrees to about 31 degrees. When there are 12 stator teeth 212, the rotor core 32 has a skew of 1.2. That is, the angle formed by the central axis J1 and the rotor teeth 322 is preferably about 21 degrees. By providing the skew in the rotor core 32, the harmonic torque due to the harmonics of the stator teeth 212 can be suppressed. Therefore, the disturbance of torque ripple is reduced. Therefore, vibration and noise can be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment.

  For example, in the above embodiment, the core back 211 may be annular. Even in this case, since the minimum cross-sectional area of the core back part 621 is equal to or larger than the minimum cross-sectional area of the tooth part 61, leakage of magnetic flux can be prevented, and a reduction in operating efficiency of the motor can be prevented. The number of cores 60 may be twelve or even more. In the case of a single-phase induction motor, in principle, the number of cores 60 is a multiple of four. When the number of cores 60 is 8 or 12, the use efficiency of the magnetic plate is particularly improved by making the outer surface 653 substantially flat.

  In the embodiment described above, the rotor core 32 may be a winding rotor in which a conducting wire is wound in the gap 325. Moreover, the end ring 33 formed of copper or a copper alloy may be integrally formed by insert molding in die casting. That is, various materials may be used for the end ring 33 as long as it is a conductor.

  The bearing portion 4 is not limited to the ball bearings 41 and 42. For example, a sleeve-shaped bearing portion may be used.

  The configurations in the above embodiment and each modification may be combined as appropriate as long as they do not contradict each other.

  The present invention can be used as a motor for various applications, and is particularly suitable for a motor for a fan, a blower, a humidifier, a water heater, an air conditioner, and a range hood.

2 Static part 3 Rotating part 4 Bearing part 21 Stator 211 Core back 212 Stator teeth 213 Coil 214 Main coil 215 Auxiliary coil 216 Crossover 22 Housing 221 Upper housing 222 Lower housing 2211 First bearing holding part 2221 Second bearing holding part 31 Shaft 32 rotor core 33 end ring 321 back yoke 322 rotor teeth 323 rotor umbrella portion 324 rotor slot open 325 gap 41 first ball bearing 42 second ball bearing 5 insulator 2121 first stator teeth 2122 second stator teeth 3221 first rotor teeth 3222 first 2 rotor teeth 3211 Center of gap

Claims (3)

A rotating part comprising a shaft and a rotor core;
A stationary part comprising a stator;
A bearing portion that rotatably supports the rotating portion with respect to the stationary portion about a central axis;
With
The stator is formed by laminating magnetic plates,
An annular core back,
A plurality of stator teeth extending radially inward from the core back;
A plurality of coils mounted in a concentrated winding manner on each of the plurality of stator teeth;
With
The plurality of coils are a plurality of main coils formed by winding main conductors wound around every other stator teeth while reversing the winding direction;
A plurality of auxiliary coils formed by auxiliary windings in which continuous conductors are wound around the stator teeth positioned between the other stator teeth while reversing the winding direction;
With
The rotor core includes a back yoke and a plurality of rotor teeth.
The plurality of rotor teeth extend radially outward from the back yoke and are arranged at equal intervals in the circumferential direction,
When the number of pairs of S and N of a plurality of magnetic poles distributed in the stator is the number of pole pairs,
The single-phase induction motor in which the number of rotor teeth and the number of pole pairs satisfy one of the following relational expressions.
(Number of rotor teeth) = (number of pole pairs) × (2n−1),
When the number of magnetic poles is 6 or more, (number of rotor teeth) = (number of pole pairs) × (2n−1) +1 or
(Number of rotor teeth) = (number of pole pairs) × (2n−1) −1
n is a natural number not including 0. In the motor according to claim 1,
The number of stator teeth is 8,
The angle formed between the rotor teeth and the central axis is 15 to 31 degrees. In the motor according to claim 1,
The number of stator teeth is 12,
The angle formed by the rotor teeth and the central axis is 21 degrees.

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