JP2020065350A - Brushless motor and method for manufacturing the same - Google Patents

Abstract

To provide a brushless motor capable of suppressing enlargement by dispersedly arranging crossover wires in each space.SOLUTION: A brushless motor 30 includes a rotor 31 having twelve slots and eight poles and rotatable about a shaft line 104, and a stator 33 disposed outside the rotor 31 in a radial direction 103. The stator 33 has a stator core 42 having a plurality of teeth 44 arranged on the same circumference about the shaft line 104 with a gap and a three-phase coil group 39 (a first coil group 91, a second coil group 92, and a third coil group 93) that are continuously wound on each tooth 44 via crossovers 91E, 92E, and 93E. The three-phase coil group 39 is delta-connected. The crossover 92E of the second coil group 92 is located closer to a first direction 102A side than the teeth 44. The crossover wires 91E and 93E of the first and the third coil groups 91 and 93 are positioned closer to a second direction 102B side than the teeth 44, respectively.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a brushless motor including a stator in which a coil group of three phases is wound around a plurality of teeth, and a method for manufacturing the brushless motor.

  Conventionally, a brushless motor including a stator in which a coil group of three phases is wound around a plurality of teeth is known. Many of such brushless motors are connected by a star connection like the one disclosed in Patent Document 1.

  The brushless motor disclosed in Patent Document 1 includes a terminal block for forming a neutral point necessary for star connection. Further, in the brushless motor disclosed in Patent Document 1, as shown in FIG. 3 of Patent Document 1, in all of the three-phase coil groups, the connecting wire between the coils is located above the tooth (the terminal block is provided). Side).

JP 2012-228136 A

  In the brushless motor disclosed in Patent Document 1, all the crossover wires and all the terminal blocks of the three-phase coil group are provided above the teeth. Therefore, a large space is required above the teeth, and the brushless motor becomes large. On the other hand, although there is a certain space below the teeth, the space is wasted because the terminal block and the crossover are not provided at all in the space.

  The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a brushless motor that can suppress an increase in size by disposing crossover wires in each space.

  (1) A brushless motor according to the present invention includes a rotor that is rotatable about an axis extending in the axial direction and a stator that faces the rotor in the radial direction of the rotor. The stator includes a stator core having a plurality of teeth arranged on the same circumference around the axis with a gap therebetween, and a three-phase coil continuously wound on each of the plurality of teeth via a connecting wire. And a group. The number M of magnetic poles of the rotor satisfies the relationship of M = 8 × n (n is a natural number), and the number T of teeth satisfies the relationship of T = 12 × n. The three-phase coil groups are delta connected. The crossover wire of the one-phase coil group of the three-phase coil group is located on the first direction side which is one direction of the axial direction with respect to the teeth. The crossover wire of the other two-phase coil group of the three-phase coil group is located on the second direction side which is the other direction of the axial direction with respect to the teeth.

  According to this configuration, the crossover wire of the one-phase coil group of the three-phase coil group is located on the first direction side with respect to the tooth, and the remaining two-phase coils of the three-phase coil group. The crossover of the group is located on the second direction side of the tooth. Therefore, the crossovers can be arranged in a space on the first direction side of the teeth and a space on the second direction side of the teeth. As a result, the crossover wires are not concentrated on one side of the tooth in the axial direction, so that the brushless motor can be prevented from becoming large.

  Further, according to this configuration, since the three-phase coil group is delta-connected, there is no neutral point. Therefore, a terminal block for forming the neutral point is unnecessary. As a result, it is possible to prevent the brushless motor from increasing in size.

  Further, according to this configuration, the three-phase coil groups are delta connected. In the delta connection, the line current is divided into two and becomes the phase current of each phase. Therefore, the current flowing through each coil in the delta connection is smaller than the current flowing through each coil in the star connection. Therefore, in the present configuration in which the three-phase coil group is delta-connected, the wire material forming the coil can be made thinner by winding around the tooth than in the configuration in which the three-phase coil group is star-connected. This facilitates winding the wire around the tooth. Further, this allows many wires to be wound around one tooth.

  Further, according to this configuration, since the two crossover wires connected to the coil wound around the teeth are located on one side and the other side of the coil in the circumferential direction, the slack of the wire material forming the coil is reduced. be able to.

  (2) For example, the stator core is formed by connecting a plurality of split cores each having a part of the plurality of teeth.

  (3) For example, a casing that has the rotor and the stator therein and that rotatably supports the rotor is provided.

  (4) The third harmonic component contained in each phase voltage of the above three-phase coil group is 10% or less of the above phase voltage.

  In this case, even if the three-phase coil group is delta connected, the circulating current flowing through the delta connection can be reduced.

  (5) The present invention comprises a rotor rotatable around an axis extending in the axial direction, and a stator facing the rotor in the radial direction of the rotor, the stator having the same circle about the axis. The rotor includes a stator core having a plurality of teeth arranged around the circumference with a gap, and a three-phase coil group continuously wound on each of the plurality of teeth via a connecting wire. Satisfy the relation of M = 8 × n (n is a natural number), and the number T of teeth satisfies the relation of T = 12 × n, and the three-phase coil group is delta-connected. The crossover wire of the one-phase coil group of the three-phase coil group is located on the first direction side which is one direction of the axial direction with respect to the teeth, and The crossover of the remaining two-phase coil group is Than the teeth is a manufacturing method of a brushless motor that is positioned in the second orientation the side which is the other direction of the axial direction. In the method for manufacturing a brushless motor according to the present invention, at least one phase coil group among the three phase coil groups is formed by starting winding a wire rod from the ends of the plurality of teeth on the axis side in the radial direction. A coil group that is not formed in the first step of the three-phase coil group by starting winding a wire rod from the first step of forming and the ends of the plurality of teeth in the radial direction on the side opposite to the axis. Forming a second step.

  The plurality of teeth are arranged on the same circumference around the axis. Therefore, normally, the number of possible winding steps of the wire rod in each tooth is smaller on the inner side (axis side) in the radial direction than on the outer side (side opposite to the axis). In addition, usually, when wound around a tooth, the wire rod is wound so as to reciprocate between the inside and the outside in the radial direction.

  In the above case, when the wire rod is started to be wound from the end portions (outer end portions) on the opposite side to the axial lines of the plurality of teeth in the radial direction, the wire rods are attached to the axial end portions (inner side) of the plurality of teeth in the radial direction. The winding of the first stage is completed at the end) and the second stage is wound toward the outer end. That is, the increase in the number of winding steps at the inner end portion precedes the increase in the number of winding steps at the outer end portion. Then, when the number of winding steps reaches the number of possible winding steps at the inner end by repeating the winding that reciprocates in the radial direction, the number of winding steps at the outer end is the number of possible winding steps from the inner end to the tooth. Despite the large number of steps, it is less than the inner edge. This reduces the number of wire rods wound around the tooth.

  On the other hand, in the above case, when the wire is started to be wound from the inner end, the number of winding steps at the outer end is increased and the number of winding steps is increased at the inner end, contrary to the above case. Be ahead of. Then, when the number of winding steps reaches the possible number of winding steps at the inner end by repeating winding in the radial direction, the number of winding steps at the outer end can be increased by one step as compared with the above case.

  According to this manufacturing method, at least one phase coil group of the three-phase coil group is formed by starting to wind the wire rod from the axial end (inner end) of the plurality of teeth in the radial direction. ing. Therefore, the number of winding stages can be increased in the at least one-phase coil group.

  According to the brushless motor of the present invention, it is possible to suppress an increase in size by disposing the crossover wires in each space.

FIG. 1 is a schematic diagram showing the configurations of the brushless motor 30 and the controller 37. FIG. 2 is a sectional view showing a II-II section of the rotor 31, the shaft 32, and the stator 33 in FIG. FIG. 3 is a diagram showing the teeth 44 and the three-phase coil group 39 over 360 ° when the stator 33 is viewed in the radial direction from the axis 104 of the shaft 32 in FIG. 2. FIG. 4 is a circuit diagram of the brushless motor 30. FIG. 5 is a cross-sectional view of the rotor 31 and the stator 33 located on one side of the shaft 32 in the radial direction 103 as viewed in the circumferential direction 101.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate. It should be noted that the present embodiment is merely an example of the present invention, and may be appropriately changed without departing from the scope of the present invention.

[Schematic configuration of brushless motor 30]
As shown in FIG. 1, the brushless motor 30 includes a shaft 32, a rotor 31, a stator 33, and a casing 36.

  The shaft 32 extends in the axial direction 102. The rotor 31 is rotatable about the axis 104 extending in the axial direction 102 around the center of the shaft 32 along the circumferential direction 101 (see FIG. 2). The axial direction 102 is a direction perpendicular to the paper surface of FIG. As shown in FIG. 2, the stator 33 is arranged to face the rotor 31 in the radial direction 103 that is orthogonal to the axial direction 102 and radially extends from the axis 104. As shown in FIG. 1, the casing 36 houses the rotor 31, the shaft 32, and the stator 33 therein. The shaft 32 is rotatably supported by the casing 36 via a bearing 52.

  The brushless motor 30 is electrically connected by a harness 38 to a controller 37 that supplies electric power.

[Rotor 31]
As shown in FIGS. 1 and 2, the rotor 31 includes a rotor core 22 having a substantially cylindrical shape. A through hole 54 is formed in the rotor core 22 so as to penetrate the rotor core 22 in the axial direction 102. The shaft 32 is press-fitted into the through hole 54. As a result, the rotor 31 and the shaft 32 rotate integrally. That is, the rotor 31 is rotatably supported by the casing 36 via the shaft 32.

  Eight through holes 63 are formed in the rotor core 22 so as to penetrate the rotor core 22 in the axial direction 102. The eight through holes 63 are formed at equal intervals along the circumferential direction 101.

  The magnet 40 is fitted into each of the eight through holes 63. That is, in this embodiment, the rotor 31 has eight magnetic poles. The eight magnets 40 are arranged so that the magnetic poles that face the outside in the radial direction 103 (in other words, the magnetic poles that face the stator 33) are alternately different poles in the circumferential direction 101.

  Note that the rotor core 22 is formed by stacking a plurality of substantially disk-shaped steel plates in the plan view shown in FIG. 2 along the axial direction 102, and the recessed and projected shapes of each steel plate are fitted to each other by caulking or the like. By doing so, they are integrally fixed.

[Stator 33]
As shown in FIGS. 1 and 2, the stator 33 is located outside the rotor 31 in the radial direction 103. The stator 33 faces the rotor 31 with a gap in the radial direction 103. That is, in the present embodiment, the brushless motor 30 is a so-called inner rotor type in which the rotor 31 is provided inside the stator 33 in the radial direction 103. The brushless motor 30 may be a so-called outer rotor type in which the rotor 31 is provided outside the stator 33 in the radial direction 103.

  The stator 33 includes a stator core 42, an insulator 45, and a three-phase coil group 39. Note that the insulator 45 is not shown in FIG. The stator 33 is formed by winding a three-phase coil group 39 around a stator core 42 having a substantially cylindrical outer shape. The stator core 42 is integrated by stacking a plurality of steel plates having a shape shown in FIG. 2 in a plan view in the axial direction 102 and connecting them by caulking.

  The stator core 42 has a core yoke 43 on the outer peripheral side. Twelve teeth 44A to 44L (collectively referred to as "teeth 44" collectively) protruding from the core yoke 43 to the center of the cylinder are evenly spaced in the circumferential direction 101 of the rotor 31 and arranged. Has been done. That is, the teeth 44 are arranged with a gap on the same circumference with the axis 104 as the center.

  As described above, in the present embodiment, the number of magnetic poles of the rotor 31 is 8 and the number of teeth 44 is 12. That is, in this embodiment, the brushless motor 30 has 12 slots and 8 poles.

  The stator core 42 is formed by connecting a plurality of split cores. In the present embodiment, the stator core 42 is composed of 12 split cores, as shown in FIG. Each split core includes a convex portion 94 and a concave portion 95. The convex portion 94 projects in the circumferential direction 101 from one end surface in the circumferential direction 101 of each split core. The recess 95 is recessed in the circumferential direction 101 from the other end surface of each split core in the circumferential direction 101. By fitting the protrusions 94 and the recesses 95 of two adjacent split cores of the split cores, the split cores are connected to each other to form the stator core 42.

  Note that in FIG. 2, twelve split cores are provided and each of the twelve split cores includes one tooth 44, but the number of split cores is not limited to twelve. For example, six split cores may be provided, and each of the six split cores may include two teeth 44. Further, the stator core 42 may be formed of one core instead of connecting the split cores.

  The insulator 45 shown in FIG. 1 includes a member arranged on one side of the stator core 42 and a member arranged on the other side in the axial direction 102. These two members are integrally molded. Then, these two members are connected so as to sandwich each of the teeth 44A to 44L. As a result, the insulator 45 externally fits each of the teeth 44A to 44L.

  As shown in FIG. 1, a coil group 39 of three phases is wound around each of the teeth 44A to 44L via an insulator 45. As shown in FIG. 2, the protruding tip end portion of each tooth 44 forms a wide portion 59 having a longer length in the circumferential direction 101 than the other portions of the tooth 44. This prevents the three-phase coil group 39 wound around the tooth 44 from coming off the tip end side of the tooth 44.

[Three-phase coil group 39]
The three-phase coil group 39 is wired as shown in FIG. FIG. 3 shows the stator 33 over 360 ° when the stator 33 is viewed in the radial direction from the center of the shaft 32 (axis 104) in FIG. 2. In FIG. 3, the coils are wound only once for each of the teeth 44A to 44L for simplification of the drawing, but in reality, they are wound a plurality of times.

  As shown in FIG. 3, the three-phase coil group 39 includes a first coil group 91, a second coil group 92, and a third coil group 93. In FIG. 3, the right end R1 and the left end L1 of the first coil group 91 are connected, the right end R2 and the left end L2 of the second coil group 92 are connected, and the right end of the third coil group 93 is connected. R3 and the left end L3 are connected.

  The first coil group 91 includes coils 91A, 91B, 91C, 91D wound around the teeth 44A, 44D, 44G, 44J. The second coil group 92 includes coils 92D, 92C, 92B and 92A wound around the teeth 44B, 44E, 44H and 44K. The third coil group 93 includes coils 93A, 93B, 93C, 93D wound around the teeth 44C, 44F, 44I, 44L. That is, each of the three-phase coil groups 39 includes four coils.

  The first coil group 91 includes a connecting wire 91E. The crossovers 91E are provided at three locations. The crossover wire 91E connects the two coils wound around the teeth 44A and 44D, connects the two coils wound around the teeth 44D and 44G, and connects the two coils wound around the teeth 44G and 44J. There is.

  The second coil group 92 includes a connecting wire 92E. The crossovers 92E are provided at three locations. The crossover 92E connects the two coils wound around the teeth 44B and 44E, connects the two coils wound around the teeth 44E and 44H, and connects the two coils wound around the teeth 44H and 44K. There is.

  The third coil group 93 includes a connecting wire 93E. The crossovers 93E are provided at three locations. The crossover 93E connects the two coils wound around the teeth 44C and 44F, connects the two coils wound around the teeth 44F and 44I, and connects the two coils wound around the teeth 44I and 44L. There is.

  As described above, each of the three-phase coil groups 39 is wound around each of the plurality of teeth 44 via the connecting wires 91E, 92E, 93E. That is, each of the three-phase coil groups 39 is continuously wound without being cut between the plurality of teeth 44.

  One end 911 and the other end 912 of the first coil group 91 are connected to the coils wound around the teeth 44A and 44J, respectively. One end 921 and the other end 922 of the second coil group 92 are connected to the coils wound around the teeth 44K and 44B, respectively. One end 931 and the other end 932 of the third coil group 93 are connected to the coils wound around the teeth 44C and 44L, respectively.

  As shown in FIG. 4, one end 911 of the first coil group 91 and the other end 932 of the third coil group 93 are connected. Further, the one end 911 and the other end 932 are electrically connected to the controller 37 by an electric wire 381 forming the harness 38. An R-phase voltage is applied from the controller 37 to the one end 911 and the other end 932.

  One end 921 of the second coil group 92 and the other end 912 of the first coil group 91 are connected. Further, the one end 921 and the other end 912 are electrically connected to the controller 37 by an electric wire 382 that constitutes the harness 38. A voltage of S phase is applied from the controller 37 to the one end 921 and the other end 912.

  One end 931 of the third coil group 93 and the other end 922 of the second coil group 92 are connected. Further, the one end 931 and the other end 922 are electrically connected to the controller 37 by an electric wire 383 that constitutes the harness 38. The controller 37 applies a T-phase voltage to the one end 931 and the other end 922.

  From the above, the three-phase coil group 39 is delta-connected as shown in FIG. Further, the three-phase coil group 39 produces a magnetic field based on the voltage applied from the controller 37. As a result, the rotor 31 rotates.

  In the present embodiment, the phase voltage of the three-phase coil group 39 shown in FIG. 4 (the phase voltage V1 of the first coil group 91, the phase voltage V2 of the second coil group 92, and the third coil group 93). The third harmonic component contained in each phase voltage V3) is 10% or less of each phase voltage V1, V2, V3. The configuration in which the third harmonic component is 10% or less of the phase voltages V1, V2, and V3 is the number of coils configuring each of the three-phase coil groups 39, the number of turns of each coil, It is determined by conducting an experiment referring to the waveform of the phase voltage while appropriately changing the position and the number of magnets.

  The third harmonic component contained in each of the phase voltages V1, V2, V3 of the three-phase coil group 39 is preferably 10% or less of each phase voltage V1, V2, V3, but 10% or more. May be large.

  As shown in FIGS. 3 and 5, the crossovers 92E of the second coil group 92, which is a one-phase coil group of the three-phase coil group 39, are located closer to the first direction 102A side than the teeth 44. is doing. The first direction 102A is one direction of the axial direction 102.

  On the other hand, the crossovers 91E and 93E of the first coil group 91 and the third coil group 93, which are the other two-phase coil groups of the three-phase coil group 39, are closer to the second direction 102B side than the teeth 44. Is located in. The second direction 102B is the other direction in the axial direction 102. That is, the second direction 102B is opposite to the first direction 102A. That is, the crossover wire 91E and the crossover wires 91E and 93E are located on opposite sides of the tooth 44 in the axial direction 102.

  Note that the one-phase coil group of the three-phase coil group 39 is not limited to the crossover wire 92E, and the other two-phase coil groups of the three-phase coil group 39 are limited to the crossover wires 91E and 93E. Absent. That is, the one-phase coil group of the three-phase coil group 39 may be the crossover wire 91E, and the other two-phase coil groups of the three-phase coil group 39 may be the crossover wires 92E and 93E. The one-phase coil group of the three-phase coil group 39 may be the crossover wire 93E, and the other two-phase coil groups of the three-phase coil group 39 may be the crossover wires 91E and 92E.

[Method for manufacturing brushless motor 30]
The brushless motor 30 is manufactured through steps of forming the rotor 31, forming the stator 33, and attaching the rotor 31 and the stator 33 to the casing 36.

  In the step of forming the rotor 31, the rotor core 22 is formed by integrally fixing the plurality of steel plates as described above. Then, the shaft 32 is press-fitted into the rotor core 22.

  In the step of forming the stator 33, the stator core 42 is formed by integrally fixing the plurality of steel plates as described above. Next, the insulator 45 is fitted onto the teeth 44 of the stator core 42. Then, as described later, the three-phase coil group 39 is wound around the tooth 44.

  The formed rotor 31 and stator 33 are attached to the casing 36 by known means. The three-phase coil group 39 and the controller 37 are electrically connected by the harness 38. Thereby, the brushless motor 30 is manufactured.

  Hereinafter, the step of forming the three-phase coil group 39 by winding the wire around the tooth 44 will be described with reference to FIG. When each of the three-phase coil groups 39 is wound around each tooth 44, the wire is wound from the end 441 and then wound substantially along the radial direction 103 toward the end 442. Here, the end portion 441 is an end portion on the axial line 104 side in the radial direction 103 of the tooth 44, and the end portion 442 is an end portion on the opposite side to the axial line 104 in the radial direction 103 of the tooth 44.

  When the winding of the wire reaches the end 442, the wire is wound substantially along the radial direction 103 toward the end 441. After that, the wire is wound while reciprocating the end portion 441 and the end portion 442 substantially along the radial direction 103. When the wire rod is wound around the tooth 44 by the maximum amount that can be wound, the wire rod is extended to the tooth 44 to be wound next. This extended line is a crossover. A coil is formed by winding the wire rod around the tooth 44 in the maximum amount. After that, the wire is wound around the tooth 44 in the same procedure, so that four coils are formed through the three connecting wires and one of the three-phase coil groups 39 is formed. The remaining two-phase coil groups 39 are similarly formed.

  In the above description, when each of the three-phase coil groups 39 is wound around each tooth 44, the wire rod is started to be wound from the end portion 441. That is, in all of the three-phase coil groups 39, the wire rod was started to be wound from the end portion 441. However, in some of the three-phase coil group 39, the wire may start winding from the end 442.

  That is, when the one-phase coil group 39 among the three-phase coil groups 39 is formed by starting the winding of the wire from the end 441, the remaining two-phase coil group 39 has the wire from the end 442. It is formed by starting to wind. When the two-phase coil group 39 of the three-phase coil group 39 is formed by starting the winding of the wire from the end portion 441, the remaining one-phase coil group 39 has the wire material from the end portion 442. It is formed by starting to wind. Further, when all the coil groups 39 of the three-phase coil group 39 are formed by starting the winding of the wire from the end 441, the coil group 39 is formed by starting the winding of the wire from the end 442. There is no such thing.

  That is, the step of forming the three-phase coil group 39 by winding the wire rod around the tooth 44 is performed by starting to wind the wire rod from the end 441 so that at least one phase coil group among the three-phase coil group 39 is formed. And a second step of forming a coil group that is not formed in the first step of the three-phase coil group 39 by starting to wind the wire from the end portion 442. If all the coil groups 39 of the three-phase coil group 39 are formed by starting the winding of the wire from the end 441, the second step is not executed.

[Operation and effect of this embodiment]
According to the present embodiment, the crossover wire 92E of the second coil group 92, which is a one-phase coil group of the three-phase coil group 39, is located closer to the first direction 102A side than the teeth 44, Crossovers 91E and 93E of the first and third coil groups 91 and 93, which are the remaining two-phase coil groups of the three-phase coil group 39, are located closer to the second direction 102B side than the teeth 44. . Therefore, the crossovers 91E, 92E, 93E can be arranged in a space closer to the first direction 102A than the tooth 44 and a space closer to the second direction 102B than the tooth 44. As a result, the crossovers 91E, 92E, 93E are not concentrated on one side of the tooth 44 in the axial direction 102, so that the brushless motor 30 can be prevented from increasing in size.

  Further, according to the present embodiment, since the three-phase coil group 39 is delta-connected, there is no neutral point. Therefore, a terminal block for forming the neutral point is unnecessary. As a result, upsizing of the brushless motor 30 can be suppressed.

  Further, according to this embodiment, the three-phase coil group 39 is delta-connected. In the delta connection, the line current is divided into two and becomes the phase current of each phase. Therefore, the current flowing through each coil in the delta connection is smaller than the current flowing through each coil in the star connection. Therefore, in the present embodiment in which the three-phase coil group 39 is delta-connected, the wire wound around the coil can be made thinner than in the configuration in which the three-phase coil group 39 is star-connected. This makes it easy to wind the wire around the coil. Further, as a result, many wires can be wound around one tooth 44.

  Further, according to the present embodiment, as shown in FIG. 3, one of the two connecting wires extending from the coil wound around each tooth 44 has one side of the coil (in FIG. 3) in the circumferential direction 101. The other of the two connecting wires extending from the coil wound around each tooth 44 extends to the other side (left in FIG. 3) of the coil in the circumferential direction 101. That is, the two crossover wires extending from the coil wound around each tooth 44 extend in the opposite direction of the circumferential direction 101 from the coil. Therefore, it is possible to reduce the slack of the wire material that constitutes the coil.

  Further, according to the present embodiment, the third harmonic component contained in each phase voltage V1, V2, V3 of the three-phase coil group 39 is 10% or less of the phase voltage V1, V2, V3. Therefore, even if the three-phase coil group 39 is delta connected, the circulating current flowing through the delta connection can be reduced.

  Further, the plurality of teeth 44 are arranged on the same circumference centered on the axis 104. Therefore, normally, the number of possible winding steps of the wire rod in each tooth 44 is smaller on the inner side (on the side of the axis 104) in the radial direction 103 than on the outer side (on the side opposite to the axis 104). Further, normally, when the wire rod is wound around the tooth 44, the wire rod is wound so as to reciprocate in the radial direction between the inner side and the outer side.

  In the above case, when the wire rod is started to be wound from the end portion (outer end portion) of the plurality of teeth 44 on the side opposite to the axis 104 of the plurality of teeth 44 in the radial direction 103, the wire rod has the axis lines 104 of the plurality of teeth 44 in the radial direction 103. The winding of the first step is completed at the end portion on the side (inner end portion), and the winding of the second step is performed toward the outer end portion. That is, the increase in the number of winding steps at the inner end portion precedes the increase in the number of winding steps at the outer end portion. Then, when the winding that reciprocates in the radial direction 103 is repeated and the number of possible winding steps is reached at the inner end, the number of winding steps at the outer end can be changed from the inner end to the teeth 44. Although there are many winding steps, the number of winding steps is smaller than the inner end. As a result, the number of wires wound around the teeth 44 decreases.

  On the other hand, in the above case, when the wire is started to be wound from the inner end, the number of winding steps at the outer end is increased and the number of winding steps is increased at the inner end, contrary to the above case. Be ahead of. Then, when the winding that reciprocates in the radial direction 103 is repeated and the number of possible winding steps is reached at the inner end, the number of winding steps at the outer end can be increased by one step compared to the above case. .

  According to this manufacturing method, at least one-phase coil group 39 of the three-phase coil group 39 winds the wire rod from the end portions (inner end portions) on the axis 104 side of the plurality of teeth 44 in the radial direction 103. Is formed by starting. Therefore, the number of winding stages can be increased in the at least one-phase coil group.

[Modification]
In the above embodiment, the number of magnetic poles of the rotor 31 was eight, but the number of magnetic poles of the rotor 31 is not limited to eight, provided that it is a multiple of eight. That is, the number M of magnetic poles of the rotor 31 may satisfy the relationship of M = 8 × n when n is a natural number.

  In the above-described embodiment, the stator core 42 includes twelve teeth 44, but the number of teeth 44 is not limited to twelve, provided that it is a multiple of twelve. The number T of the teeth 44 may satisfy the relationship of T = 12 × n, which is an expression including n described above.

30 ... Brushless motor 31 ... Rotor 33 ... Stator 39 ... Coil group 42 ... Stator core 44 ... Teeth 91E ... Crossover 92E ... Crossover 93E ... Crossover 102 ... axial direction 102A ... 1st direction 102B ... 2nd direction 104 ... axial line

Claims (5)

A rotor that can rotate around an axis extending in the axial direction,
A stator facing the rotor in the radial direction of the rotor,
The stator is
A stator core having a plurality of teeth arranged with a gap on the same circumference about the axis,
And a group of three-phase coils continuously wound on each of the plurality of teeth via a connecting wire,
The number M of magnetic poles of the rotor satisfies the relationship of M = 8 × n (n is a natural number), and the number T of teeth satisfies the relationship of T = 12 × n,
The three-phase coil group is delta connected,
The crossover wire of the one-phase coil group of the three-phase coil group is located on the first direction side which is one direction of the axial direction with respect to the teeth,
The crossover wire of the coil group of the other two phases of the coil group of the three phases is located on the second direction side which is the other direction in the axial direction with respect to the teeth.   The brushless motor according to claim 1, wherein the stator core is formed by connecting a plurality of split cores each having a part of the plurality of teeth.   The brushless motor according to claim 1 or 2, further comprising a casing that has the rotor and the stator inside and that rotatably supports the rotor.   The brushless motor according to claim 1, wherein a third harmonic component included in each phase voltage of the three-phase coil group is 10% or less of the phase voltage. A rotor that is rotatable around an axis extending in the axial direction and a stator that faces the rotor in the radial direction of the rotor are provided, and the stator is provided with a gap on the same circumference centered on the axis. A stator core having a plurality of teeth arranged and a three-phase coil group continuously wound on each of the plurality of teeth via a connecting wire are provided, and the number of magnetic poles M of the rotor is M = 8 × n ( n is a natural number), and the number T of teeth is T = 12 × n, the three-phase coil group is delta-connected, and the three-phase coil group The crossover wire of the one-phase coil group is located on the first direction side, which is one direction in the axial direction with respect to the teeth, and the remaining two-phase coils of the three-phase coil group. The crossover of the group is from the teeth Is a method for manufacturing a brushless motor located on the second direction side, which is the other direction in the axial direction,
A first step of forming a coil group of at least one phase among the coil groups of three phases by starting to wind a wire rod from the ends of the plurality of teeth on the axis side in the radial direction;
A second step of forming a coil group that is not formed in the first step of the three-phase coil group by starting to wind the wire from the ends of the plurality of teeth in the radial direction opposite to the axis. A method for manufacturing a brushless motor including:

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