JP6002617B2 - Permanent magnet synchronous machine - Google Patents

Description

  The present invention relates to a permanent magnet synchronous machine, and more particularly to a permanent magnet synchronous machine having a permanent magnet embedded therein.

  In the permanent magnet synchronous machine, an interior permanent magnet (hereinafter referred to as IPM) structure in which a permanent magnet is embedded in a rotor is widely adopted. In IPM, reluctance torque can be used in addition to magnet torque, but it is effective to increase the magnet magnetic flux generation section on the rotor gap facing surface in order to further increase the torque.

  In patent document 1, in order to adjust a magnetic flux generation | occurrence | production area, it is set as the structure which has the magnetic pole part which protrudes in the outer peripheral part of a U-shaped permanent magnet. According to Patent Document 1, it is possible to reduce the leakage magnetic flux from the magnet end by projecting the d-axis region with respect to the q-axis region, and to increase the torque by concentrating the magnetic flux on the magnetic pole portion. it can.

  In the permanent magnet synchronous machine having the IPM structure, the induced electromotive force waveform changes to a trapezoidal wave shape or a sine wave shape depending on the rotor shape. When driving a permanent magnet motor with trapezoidal induced electromotive force, torque pulsation and noise increase, and iron loss increases due to conduction of current containing higher-order components depending on the number of pole pairs. This causes a problem of lowering.

  In particular, since the holding force of the ferrite magnet is about 1/3 that of the neodymium magnet, it is necessary to increase the magnet thickness and cover the decrease in holding force. However, as a result, the inter-pole portion of the rotor-facing gap-facing surface becomes a magnetic flux-free section. For this reason, there is a problem that the shape of the induced electromotive force waveform cannot be uniquely determined by the method of adjusting the magnet arrangement as in Patent Document 1.

JP2002-136011

  SUMMARY OF THE INVENTION An object of the present invention is to achieve low vibration and low noise, reduce iron loss, and improve efficiency in a permanent magnet synchronous machine using a ferrite magnet and a drive system using the same.

  A permanent magnet motor according to the present invention includes a rotor having a permanent magnet, and a stator having teeth and being arranged with a gap in the outer circumferential direction of the rotor, and the rotor includes the teeth and Forming a first outer peripheral portion in which a gap between the teeth is a first distance and a second outer peripheral portion in which a gap between the teeth is a second distance larger than the first distance, and forming the second outer periphery The portion is formed at a position facing the end portion of the permanent magnet with respect to the radial direction from the rotation axis center, and an angle of the rotation axis center corresponding to the width of the teeth is defined as θs. The angle of the rotation axis center corresponding to the opening is defined as θp, the angle of the rotation axis center corresponding to the first outer peripheral portion of the rotor is defined as θa, and θs ≧ θp> θa. .

  According to the present invention, noise and vibration are reduced, iron loss is reduced, and efficiency is improved.

1 is an exploded perspective view of a permanent magnet motor 100. FIG. 1 is a perspective view of a permanent magnet motor 100. FIG. FIG. 3 is a cross-sectional view of the permanent magnet motor 100 shown in FIG. 2 cut along a plane A and viewed from the arrow direction. It is an expanded sectional view of the part B of FIG. It is an expanded sectional view showing other embodiments of a method of forming the 2nd peripheral part 22. The magnetic flux density distribution Bpm (x _r ) of the gap by the permanent magnet 3 is shown. It is a schematic diagram for demonstrating the magnetic flux amount linked to the one phase coil in the case where concentrated winding 2 pole 3 slot series is made into object. It is a figure which shows the composition rate of the quintic component with respect to the 1st outer peripheral part 21, and a 7th-order component. It is a figure which shows the induced electromotive force waveform in (theta) a = 69 degrees. It is a figure which shows the induced electromotive force waveform in (theta) a = 123 degree. It is a figure which shows the iron loss with respect to a frequency.

  An embodiment of the present invention will be described below with reference to the drawings. In the following description, the same symbols are attached to the same components. Their names and functions are the same, and duplicate descriptions are avoided. Further, in the following description, the inner rotor is targeted, but the effect of the present invention is not limited to the inner rotor, and can be applied to an outer rotor having a similar configuration. is there.

  FIG. 1 is an exploded perspective view of the permanent magnet electric motor 100. FIG. 2 is a perspective view of the permanent magnet electric motor 100. FIG. 3 is a cross-sectional view of the permanent magnet motor 100 shown in FIG.

  The rotor 1 includes a shaft 5, permanent magnets 3 a to 3 f, and a rotor core 2. The shaft 5 is inserted into the shaft insertion hole 6 of the rotor core 2. The permanent magnets 3a to 3f are inserted into the magnet housing holes 4a to 4f of the rotor core 2.

  The stator 10 forms a space for housing the rotor 1 in the center, and has teeth 12a to 12i so as to surround the space. Windings (not shown) are wound around the teeth 12a to 12i. The present embodiment relates to a permanent magnet synchronous machine having an adder-type rotor 1 composed of permanent magnets 3 arranged to form a plurality of poles.

  4 is an enlarged cross-sectional view of a portion B in FIG. The part B illustrated in FIG. 4 shows an example of the configuration of the poles of the present embodiment, and the other poles have the same configuration.

  The rotor core 2 forms a magnet accommodation hole 4a. The magnet accommodation hole 4a is formed with a recess that opens toward the side where the stator 10 is disposed. The rotor core 2 may be composed of laminated steel plates stacked in the axial direction, may be composed of a dust core, or may be composed of an amorphous metal or the like.

  The permanent magnet 3a accommodated in the magnet accommodating hole 4a forms a bent portion 30 and a bent portion 31 in the circumferential direction per pole. The permanent magnet 3a is formed to extend toward the pole end 34 along the direction perpendicular to the magnetization direction 33 of the permanent magnet 3a, starting from the bent portion 30. The permanent magnet 3a is formed so as to extend toward the pole end 36 along the direction perpendicular to the magnetization direction 35 of the permanent magnet 3a, starting from the bent portion 31.

  The permanent magnet 3a may be configured to form three or more bent portions, may be U-shaped, or may be V-shaped consisting of two magnets. By adopting the magnet shape described here, the surface area of the magnet magnetic flux generation surface is increased, and the core cross-sectional area 20 of the outer peripheral portion in the radial direction of the permanent magnet 3 is increased, so that reluctance torque can be actively utilized. It becomes possible.

  Further, the permanent magnet 3 may be integrally formed without being divided in the circumferential direction per pole, or a plurality of permanent magnets 3 may be arranged in the circumferential direction. Further, a plurality of parts may be divided in the axial direction, or may be formed integrally without being divided.

  As the permanent magnet 3, a permanent magnet having a relatively low holding force and residual magnetic flux density, such as a ferrite magnet, is used. However, this example is limited to a holding force of 400 kA / m, such as a ferrite magnet, but SmFeN (holding force is 800 kA / m) or neodymium bonded magnet (coercive force 600 kA / m). Good. In other words, the use of a permanent magnet having a smaller holding force than a neodymium magnet has the effects of this embodiment.

  The rotor 1 forms a first outer peripheral portion 21 in which a gap between the rotor 12 and the tooth 12 a is a first distance 41. Further, the rotor 1 forms a second outer peripheral portion 22 in which a gap between the rotor 12 and the teeth 12 a becomes a second distance 42 that is larger than the first distance 41. The second outer peripheral portion 22 is formed at a position facing the end portions 34 and 36 of the permanent magnet 3 in the radial direction from the center of the rotation axis.

  Here, the angle of the rotation axis center corresponding to the width of the teeth 12a is defined as θs. The angle of the rotation axis center corresponding to the opening of the permanent magnet 3 is defined as θp. Here, both ends of θp are defined as locations where the magnetic flux of the permanent magnet 3 is switched. Specifically, since the end portions 34 and 36 have a much smaller magnetic flux than the other surfaces of the permanent magnet 3, both ends of θp are determined by the magnitude of the magnetic flux on each surface of the permanent magnet 3.

  The angle of the rotation axis center corresponding to the width of the first outer peripheral portion 21 is defined as θa. The teeth 12a, the opening of the permanent magnet 3, and the first outer peripheral portion 21 are formed so as to have a relationship of θs ≧ θp> θa.

  Here, if the induced electromotive force waveform generated in the permanent magnet motor 100 due to the rotation of the rotor 10 has a shape close to a sine wave, the vibration and noise are reduced, and the iron loss is reduced and the efficiency is improved. be able to. On the other hand, when a ferrite magnet is used for the rotor 10 as compared with a neodymium magnet as in this embodiment, it is necessary to use a thick ferrite magnet in order to generate a desired magnetic flux.

  However, if a thick ferrite magnet is used, there is a risk of causing a sudden change in magnetic flux in the rotor 10, and it is difficult for the induced electromotive force waveform to have a shape close to a sine wave. Specifically, almost no magnetic flux is generated at the end portions 34 and 36 of the permanent magnet 3 shown in FIG. That is, by using a thick ferrite magnet, the magnetic flux change from the end portions 34 and 36 of the permanent magnet 3 to the iron core cross-sectional area 20 becomes abrupt, and the induced electromotive force waveform is unlikely to have a shape close to a sine wave.

  On the other hand, the permeability of air existing between the rotor 10 and the teeth 12 a is smaller than the permeability of the rotor core 2. Therefore, the rotor 1 of the present embodiment forms the second outer peripheral portion 22 in which the gap between the teeth 12a becomes the second distance 42 that is larger than the first distance 41. Thereby, since the change of magnetic flux becomes large gradually in order of the end part 34 of the permanent magnet 3, the 2nd outer peripheral part 22, and the 1st outer peripheral part 21, the change of magnetic flux becomes smooth and an induced electromotive force waveform is sine. It becomes easy to become a wave-like shape. As a result, the permanent magnet motor 100 can reduce vibration and noise, reduce iron loss, and improve efficiency.

  In the present embodiment shown in FIG. 4, the rotational axis center angle θs corresponding to the width of the tooth 12 a is larger than the rotational axis center angle θp corresponding to the opening of the permanent magnet 3. , Θs and θp are the same, the same effects as in the present embodiment occur.

  As shown in FIG. 4, the rotor core 2 forms a first gap switching portion 51 and a second gap switching portion 52 that connect the first outer peripheral portion 21 and the second outer peripheral portion 22. The first gap switching portion 51 and the second gap switching portion 52 form a step shape so that the first outer peripheral portion 21 is closer to the tooth 12 a than the second outer peripheral portion 22. That is, the second outer peripheral portion 22 forms a circular shape in the cross-sectional shape of the rotor core 2, while the first outer peripheral portion 21 is formed as a protruding portion protruding from the circular shape.

  Another forming method is shown in FIG. The first outer peripheral portion 21 forms a circular shape in the cross-sectional shape of the rotor core 2, while the second outer peripheral portion 22 is formed by cutting portions 53 and 54 from the circular shape.

  The operation and effect of the rotor core 2 configured as described above will be described below.

  Hereinafter, the theoretical formulas of the fifth and seventh order components of the induced electromotive force will be derived, and the principle of obtaining the functions and effects of this embodiment will be described.

First, the magnetic flux density distribution Bpm (x _r ) of the gap by the permanent magnet 3 is as shown in FIG. Here, _xr is the circumferential position (electrical angle, deg.) Of the outer periphery of the rotor. At this time, the spatial ν-order component of Bpm (x _r ) is expressed by the following equation.

(1)
When the rotor is rotating at the angular velocity ω1, the relationship between the stator coordinate x _s and the rotor coordinate x _r is
(2)
Therefore, the magnetic flux density distribution Bpm (x _s ) of the gap by the permanent magnet 3 viewed from the stator coordinate system is as follows.

(3)
In the expression (3), since the spatial order ν of the gap magnetic flux density distribution by the permanent magnet 3 and the time order μ are equal, both are expressed by μ.

  Next, in the case of concentrated winding 2-pole 3-slot series, the time μ-order component Φc, μ of the amount of magnetic flux interlinked with the one-phase coil is -θt / 2 to θt / 2 as shown in FIG. It is obtained from the integration interval.

(Four)
Here, l: Core axial length Therefore, the induced electromotive force waveform μ order component uc, μ due to the magnetic flux is expressed by the following equation.

(Five)
Here, Nc: number of turns of one coil From the above, the amplitude ratio kμ of the μ-order component to the fundamental wave component is expressed by the following equation.

(6)
In the concentrated winding, θt is 120 ° (electrical angle) at the maximum, and the relationship between θa and kμ at this time is obtained as shown in FIG.

  From Equation (6), the theoretical maximum values of the 5th and 7th components are 0.200 and 0.143, respectively, so that the sum of the 5th and 7th components is less than this average value of 0.171. Thus, the induced electromotive force waveform can be approximated to a sine wave shape. As shown in FIG. 10, the iron loss varies greatly depending on the frequency. For example, the iron loss is about 2.6 W at the fundamental wave frequency of 100 Hz, whereas the iron loss of 500 Hz and 700 Hz which are the fifth and seventh orders of the fundamental wave. Are about 33W and 55W respectively, more than 10 times. For this reason, high efficiency is realized by reducing the fifth and seventh order components having a low composition ratio. From Fig. 10, if the fundamental frequency is 50Hz or more, the increase in iron loss due to the 5th order (250Hz) and 7th order components (350Hz) is remarkable, and it shows a great effect in the permanent magnet synchronous machine driven under this operating condition. To do.

  From FIG. 8, it can be seen that θa is preferably set to 80 ° ≧ θa ≧ 50 ° or 160 ° ≧ θa ≧ 135 ° in electrical angle in order to make the induced electromotive force waveform sinusoidal. Even when θa other than the above is adopted, it is possible to reduce the sum of the fifth-order and seventh-order components, but for example, when θa = 10 °, the fundamental wave is clear as is clear from Equation (6). It can be said that it is unsuitable because the components are significantly reduced.

  FIG. 8 shows the case of θt = 120 °. However, even when θt = 90 °, only the value of the induced electromotive force is reduced, and the condition of θa for reducing the fifth and seventh order components. Will not change. However, if θt is reduced, the fundamental wave component is reduced. Therefore, θt should be in the range of 90 ° <θt <120 °, and is preferably closer to 120 °.

  FIG. 9A shows an induced electromotive force waveform at θa = 69 ° when the present embodiment is applied, and FIG. 9B shows a waveform at θa = 123 °. From FIG. 9A, it is understood that a sinusoidal induced electromotive force waveform can be generated by setting θa = 69 °. As a result, even when a thick ferrite magnet is applied, the vibration and noise can be reduced, and the iron loss can be reduced to improve the efficiency.

  In this embodiment, the concentrated winding 2-pole 3-slot system is targeted, but the value of the sin second term shown in equation (6) is different even for fractional slots such as the concentrated winding 4-pole 3-slot system. Therefore, by setting 80 ° ≧ θa ≧ 50 ° or 160 ° ≧ θa ≧ 135 °, a sinusoidal induced electromotive force waveform can be generated in the same manner. Also for distributed winding, only the value of the sin second term shown in Equation (6) is different, and 80 ° ≧ θa ≧ 50 ° or 160 ° ≧ θa ≧ 135 ° is similarly applied to a sinusoidal wave shape. The induced electromotive force waveform can be generated.

  According to the present embodiment, the fifth and seventh order components of the induced electromotive force due to the magnet magnetic flux can be reduced, that is, a sinusoidal induced electromotive force waveform can be obtained even when a ferrite magnet is applied. Reduces iron loss and improves efficiency while achieving vibration.

  The stator core 11 has a tooth 12a and a tooth 12b adjacent to the tooth 12a. The thickness 37 of the permanent magnet 3 is determined by a distance 14 between the end of the tooth 12a and the end of the tooth 12b. Is also formed large. By forming the first outer peripheral portion 21 and the second outer peripheral portion 22 with respect to such a configuration, the effect of obtaining a sinusoidal induced electromotive force waveform is increased.

  In this embodiment, a sinusoidal induced electromotive force waveform including the fifth and seventh harmonic components can be generated by setting 80 ° ≧ θa ≧ 50 ° or 160 ° ≧ θa ≧ 135 °. Due to the influence of the 5th and 7th components, the harmonic 5th and 7th components can be reduced in the current waveform energized from the inverter to the permanent magnet synchronous machine. Even in 180 ° energization control, it is possible to improve efficiency by reducing iron loss as well as reducing vibration and noise.

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Rotor core, 3a thru | or 3f ... Permanent magnet, 4a thru | or 4f ... Permanent magnet insertion hole, 5 ... Shaft, 6 ... Shaft insertion hole, 10 ... Stator, 11 ... Stator iron core, 12a thru | or 12i ... Teeth, 20 ... Iron core cross-sectional area, 21 ... First outer periphery, 22 ... Second outer periphery, 30 ... Bend, 31 ... Bend, 33 ... Magnetization direction, 34 ... End, 35 ... Magnetization direction, 36 ... End, 41 ... First distance, 42 ... Second distance, 51 ... First gap switching section, 52 ... Second gap switching section, 53 ... Part, 54 ... Part, 100 ... Permanent magnet motor

Claims (6)

A rotor having a permanent magnet having a property of holding power smaller than that of a neodymium magnet;
A stator having teeth and being arranged via a gap in the outer circumferential direction of the rotor,
In the cross section in the vertical direction of the rotation axis direction of the rotor, the permanent magnet is configured such that the cross-sectional shape of the permanent magnet forms a recess that opens toward the side where the stator is disposed,
The rotor has a first outer peripheral portion in which a gap between the teeth is a first distance, a second outer peripheral portion in which a gap between the teeth is a second distance larger than the first distance, and Form the
The second outer peripheral portion is formed at a position facing the end portion of the permanent magnet with respect to the radial direction from the center of the rotation axis,
Angle θs of the rotation axis corresponding to the width of the teeth, Angle θp of the rotation axis corresponding to the opening of the permanent magnet, Angles θa, θs of the rotation axis corresponding to the first outer peripheral portion of the rotor A permanent magnet motor having a relationship of ≧ θp> θa. The permanent magnet motor according to claim 1,
The permanent magnet motor is a permanent magnet motor that is a ferrite magnet. The permanent magnet motor according to claim 1 or 2,
The stator has a first tooth and a second tooth adjacent to the first tooth,
The permanent magnet motor has a thickness of the permanent magnet that is greater than a distance between an end portion of the first tooth and an end portion of the second tooth. The permanent magnet motor according to any one of claims 1 to 3,
θa is a permanent magnet motor having an electrical angle of 80 ° ≧ θa ≧ 50 ° or 160 ° ≧ θa ≧ 135 °. The permanent magnet motor according to any one of claims 1 to 4,
The rotor forms a gap switching portion that connects the first outer peripheral portion and the second outer peripheral portion,
The air gap switching portion is a permanent magnet electric motor formed so as to have a step shape between the first outer peripheral portion and the second outer peripheral portion. The permanent magnet motor according to any one of claims 1 to 5,
θs is a permanent magnet motor that has an electrical angle of 90 ° <θt <120 °.