JP2013229958A - Synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double rotor type synchronous motor in which cogging ripple is reduced, and ring winding can be employed even if the number of slots in a stator and the number of magnetic poles of a rotor are different on the inside and outside.SOLUTION: The synchronous motor includes a stator having a first stator tooth part 52 on the radial outside and a second stator tooth part 53 on the radial inside, a first rotor 56 disposed to face the first stator tooth part 52, and a second rotor 57 disposed to face the second stator tooth part 53. The number of slots Nsof the first stator tooth part 52, the number of slots Nsof the second stator tooth part 53, the number of magnetic poles Npof a first rotor, and the number of magnetic poles Npof a second rotor are set to satisfy a relational expression Ns±(Np/2)=2m, Ns=(Ns)/n, Np=2Ns×{(1/n)-1}+Np, where m is an integer of 1 or more, and n is an integer of 2 or more.

Description

  The present invention relates to a synchronous motor for servo applications used in machine tools and the like, and in particular, the number of stator slots that realizes a reduction in the amount of copper used in winding of a synchronous motor that generates a large torque at a low speed and a reduction in cogging ripple. And the number of rotor magnetic poles, and a winding method.

  FIG. 5 shows a cross-sectional view of the main part of a conventional synchronous motor and a method of winding the stator. The stator 100 of the synchronous motor includes a tooth portion 102 provided on the magnetic body 101 and a slot 103 formed between the tooth portions. In addition, a rotor 107 is provided between the inner peripheral surface of the stator 100 via a gap. The rotor 107 is configured by fitting a magnetic body 105 into a ring 104 and arranging and fixing a permanent magnet 106. As shown in FIG. 5, the stator winding method is such that one-phase winding is wound in the circumferential direction so as to straddle between the slots 103, and is generally called distributed winding. . Synchronous motors having such distributed winding stators are generally less susceptible to torque ripple, so that the rotor can be smoothly rotated and high torque can be achieved in a low rotation range.

  In the prior art, the distributed winding stator can smoothly rotate the rotor and enables high torque in the rotation region. However, since the distributed winding is wound so that the winding straddles between the slots, the volume of the coil end becomes large and it is difficult to reduce the size of the electric motor. Moreover, since the amount of copper used as the winding material is large, there is a problem that the winding resistance and copper loss increase, and the motor easily generates heat.

  On the other hand, there is a stator having an annular winding for winding the winding in an annular shape as in Patent Document 1. The synchronous motor having the stator of Patent Document 1 does not have windings straddling between slots, and the windings do not overlap with each other. Therefore, the volume of the coil end is reduced, and the motor can be reduced in size. In addition, the amount of copper used is reduced, the winding resistance and copper loss are reduced, and the heat generation of the motor is reduced. Incidentally, the phase of the current flowing through the winding of the annular winding is the same as that of the distributed winding.

  Furthermore, an electric motor including a stator having an annular winding, an inner rotor, and an outer rotor (hereinafter referred to as an annular winding double rotor type motor) is disclosed as in Patent Document 2. The annular double rotor type motor has two tooth portions 12 and 13 projecting inward and outward in the radial direction from the stator, and inner and outer slots 16 and 17 formed between the tooth portions. The stator 10 is configured to have two rotors having permanent magnets 22 and 32 bonded to the inner side and the outer side through a certain gap with respect to the tooth portions 12 and 13 of the stator 10. (Refer to FIG. 1 of Patent Document 2 for the figure of the annular winding double rotor type motor and the number of the component.)

Japanese Patent No. 3630991 Japanese Patent No. 4670871

  Generally, in an electric motor having an annular winding stator as in Patent Document 1, a cogging ripple is generated due to a permeance change between a stator slot and a magnetic pole of a rotor. In addition, an annularly wound double rotor type electric motor as in Patent Document 2 generally has the same number of slots in the inner and outer slots of the stator, and the number of magnetic poles of the inner and outer permanent magnets of the rotor. Only the same number of cases can be adopted.

  Therefore, the present invention devises the number of stator slots, the number of rotor magnetic poles, and the positional relationship of the synchronous motor, so that even if the number of stator slots and the number of rotor magnetic poles are different between the inner side and the outer side in a double rotor type motor, The purpose is to reduce the cogging ripple.

A synchronous motor according to the present invention includes a stator made of a soft magnetic material, and first and second rotors having a difference in magnetic resistance in the rotation direction and having permanent magnets on the surface or inside thereof. The stator includes a first stator tooth portion that forms a slot that opens radially outward, and a second stator tooth that forms a slot that opens radially inside. And a stator yoke portion common to the first and second stator tooth portions, and the first rotor is disposed so as to face the first stator tooth portion, The second rotor is disposed so as to face the second stator tooth portion, and a slot formed by the first stator tooth portion and a slot formed by the second stator tooth portion. the winding is wound, the number of slots Ns 1 of the first stator _teeth, and a second stator The number of slots Ns ₂ parts, the first rotor magnetic poles Np _1, and the second rotor poles Np ₂ is an integer of 1 or more m, when n an integer of 2 or more,
_{Ns 1 ± (Np 1/2} ) = 2m
Ns ₂ = (Ns ₁ ) / n
Np ₂ = 2 · Ns ₁ × {(1 / n) −1} + Np ₁
The relational expression is set so as to hold.

  In a preferred aspect, the first straight line passing through the circumferential center and the rotation center of one first stator tooth portion is located on the opposite side of the one first stator tooth portion across the yoke portion. An angle Δθ formed by the second straight line passing through the circumferential center of the second stator tooth portion and the rotation center is 0 <Δθ <(2π / Ns2) [rad].

  According to the present invention, by designing a synchronous motor that satisfies the above relational expression, it is possible to employ an annular winding even when the number of stator slots and the number of rotor magnetic poles are different between the inside and the outside. Further, by arranging a line passing through the center of rotation and the center of the first stator tooth portion and a line passing through the center of rotation and the center of the second stator tooth portion so that the above relational expression is satisfied, the stator slot It is possible to reduce cogging ripple caused by a permeance change between the magnetic poles of the rotor and the rotor.

It is sectional drawing of the synchronous motor in case of m = 1 and n = 2 with the stator of the annular winding which concerns on the 1st Embodiment and 2nd Embodiment of this invention. FIG. 2 is a partial view showing a stator winding method in FIG. 1. It is the figure which showed the drive method of the synchronous motor which concerns on this embodiment. It is the A section enlarged view of FIG. It is sectional drawing of the synchronous motor which has the stator of the distributed winding which concerns on a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 shows a synchronous motor having an annular winding stator according to the first and second embodiments when m = 1 and n = 2. FIG. 2 is a view showing a winding method of the stator of the synchronous motor shown in FIG. FIG. 3 is a diagram illustrating a method for driving the synchronous motor according to the present embodiment. The present embodiment will be described with reference to FIGS. M is not necessarily n.

  First, the structure will be described. This electric motor has a stator 50 and a rotor made of a soft magnetic material. The stator 50 includes a first stator tooth portion 52, a second stator tooth portion 53, and a stator yoke portion 51 common to the first and second stator tooth portions 52, 53. Yes. The first stator tooth portion 52 has an opening portion that opens radially outward, and the second stator tooth portion 53 has an opening portion that opens radially inward. A first slot 54 is provided between each first stator tooth portion 52, and a second slot 55 is provided between each second stator tooth portion 53.

  In addition, the rotor is provided with a first rotor 56 provided to face the first stator tooth portion 52 and a second rotor 57 provided to face the second stator tooth portion 53. And. These rotors have a difference in magnetic resistance in the direction of rotation, and have permanent magnets on the surface or inside.

  As shown in FIG. 2, the winding is wound around the first slot 54 and the second slot 55 in an annular shape so as to straddle the stator yoke portion.

In the electric motor according to the present embodiment, the combination of the number of slots of the stator and the number of magnetic poles of the rotor is a special combination. Specifically, Np ₁ the number of magnetic poles of the first number of slots Ns _second stator Ns1 the number of slots of the teeth 52, and the second stator teeth 53, the first rotor 56, and a When the number of magnetic poles of the second rotor 57 is Np ₂ , m is an integer of 1 or more and n is an integer of 2 or more, all of the following formulas 1 to 3 are established.
_{Ns 1 ± (Np 1/2} ) = 2m Formula 1
Ns ₂ = (Ns ₁ ) / n Equation 2
Np ₂ = 2 · Ns ₁ × {(1 / n) −1} + Np ₁ Formula 3

For example, in the case of the electric motor shown in FIG. 1, the number of magnetic poles Np ₁ of the first rotor 56 is 32 poles, and the number of magnetic poles Np ₂ of the second rotor 57 is 14 poles. Further, the slot number Ns _{1 of} the first stator tooth portion 52 is 18 slots, and the slot number Ns _{2 of} the second stator tooth portion 53 is 9 slots.

  Next, an outline of the driving method will be described. Since the first rotor 56 and the second rotor 57 have different numbers of magnetic poles, the synchronization frequencies are different. Although not particularly illustrated, driving is possible by superimposing currents in consideration of the phase and frequency corresponding to the first rotor 56 and the second rotor 57. In addition, since each rotor can be rotated mechanically independently, by applying a current having a phase and frequency corresponding to the first rotor 56 or the second rotor 57, the first rotor 56, It is also possible to rotate the second rotor 57 alone.

  Further, the first rotor 56 disposed radially outward has a high torque because of a large moment of inertia and a large number of magnetic poles, but has a high induced voltage and can rotate only at a low speed. Further, the second rotor 57 arranged inward in the radial direction has a small moment of inertia and a small number of magnetic poles, so that it can rotate at a high speed, but only a low torque is generated. By using the two rotors connected to the rotary shaft by a drive mechanism such as a clutch, the characteristics of the respective rotors can be utilized.

  This will be specifically described with reference to FIG. The stator 50 is fixed and restrained to the flange 60. The first rotor 56 and the second rotor 57 are connected by a clutch 62 fixed to the rotating shaft 61. When using a synchronous motor as a positioning application in a machine tool, a high torque is required. In this case, the first rotor 56 and the second rotor 57 are connected to the rotary shaft 61 via the clutch 62. As a result, the torques of the two rotors can be added together and positioned with high torque. Next, when the synchronous motor is used for a turning application like a main spindle of a lathe, high speed rotation is required. In this case, the first rotor 56 having a large number of magnetic poles is disconnected from the clutch, and only the second rotor 57 is connected to the rotating shaft 61. Thereby, it is possible to turn at high speed. The drive mechanism that connects the first rotor 56, the second rotor 57, and the rotating shaft 61 may be a mechanical structure using mechanical parts or an electric structure using control.

  As described above, according to the present embodiment, the number of teeth of the first stator and the second stator is different, but the number of magnetic poles configured in the stator by the respective rotor magnetic poles is the same. An annular winding is possible. Therefore, it is possible to take advantage of the characteristics of the annular winding, such as downsizing by reducing the coil end volume, winding resistance by reducing the amount of copper used in winding, and reduction in copper loss.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a view showing a synchronous motor in the case of m = 1 and n = 2 having an annularly wound stator according to the first and second embodiments. FIG. 4 is an enlarged view of part A in FIG. In the second embodiment, compared with the first embodiment, the cogging torque generated by the permeance change between the stator slot and the magnetic pole of the rotor can be reduced.

  In the case of n = 2, cogging ripple is generated due to permeance change between the first rotor 56-first stator and the second rotor 57-second stator, the stator slot, and the magnetic pole respectively. To do. On the other hand, as shown in FIG. 4, the angle difference Δθ is given to one of the stator tooth portions in the range of 0 <Δθ <(2π / Ns2) [rad]. In other words, the straight line connecting the circumferential center of one first stator tooth portion 52 and the center of rotation and the second stator tooth portion 53 corresponding to the first stator tooth portion 52. An angle Δθ formed by a straight line connecting the center in the circumferential direction and the rotation center is set to 0 <Δθ <(2π / Ns2). Note that n is not limited to 2, and may be an integer of 2 or more.

  In this way, by providing an angle difference between the line passing through the center of the first stator tooth portion and the line passing through the center of the second stator tooth portion, cogging ripples generated in the respective rotor and stator are canceled out. And the cogging torque generated in the entire motor can be reduced.

  50 Stator, 51 Stator Yoke, 52 First Stator Teeth, 53 Second Stator Teeth, 54 First Slot, 55 Second Slot, 56 First Rotor, 57 Second Rotor, 60 flange, 61 rotating shaft, 62 clutch, 100 stator, 101 magnetic body, 102 teeth, 103 slot, 104 ring, 105 magnetic body, 106 permanent magnet, 107 rotor.

Claims (2)

A synchronous motor comprising a stator made of a soft magnetic material, and first and second rotors having a level difference in magnetic resistance in the rotation direction and having permanent magnets on the surface or inside thereof,
The stator includes a first stator tooth portion that forms a slot that opens radially outward, a second stator tooth portion that forms a slot that opens radially inside, and A stator yoke portion common to the first and second stator tooth portions,
The first rotor is disposed so as to face the first stator tooth portion,
The second rotor is disposed so as to face the second stator tooth portion,
A winding is wound around the slot formed by the first stator tooth portion and the slot formed by the second stator tooth portion,
The number of slots Ns _second slot number Ns ₁ of the first stator teeth, and the second stator teeth, the first rotor magnetic poles Np _1, and the second rotor poles Np ₂ is, m Is an integer greater than or equal to 1, and n is an integer greater than or equal to 2,
_{Ns 1 ± (Np 1/2} ) = 2m
Ns ₂ = (Ns ₁ ) / n
Np ₂ = 2 · Ns ₁ × {(1 / n) −1} + Np ₁
The relational expression of
A synchronous motor characterized by that. In the synchronous motor according to claim 1,
A first straight line passing through a circumferential center and a rotation center of one first stator tooth portion and the second fixing located on the opposite side of the one first stator tooth portion across the yoke portion A synchronous motor characterized in that an angle Δθ formed by a second straight line passing through the center in the circumferential direction of the child tooth portion and the rotation center is 0 <Δθ <(2π / Ns2) [rad].

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