JP2015226371A - Permanent magnet embedded rotary electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce windage loss of a rotor, in a permanent magnet embedded dynamo-electric machine including a rotor not having a side bridge.SOLUTION: Two slots 2 penetrating in the direction of the rotational axis are provided per pole in the circumferential direction of a rotor 1 for a plurality of poles, and a permanent magnet 3 is embedded in each slot 2. The rotor 1 has a notch 10 for interconnecting the end on the side of an adjacent pole with the outer periphery of the rotor 1 in the two slots 2 of each pole. The notch 10 is filled with a filling member 4 composed of a nonmagnetic material. The notch 10 plays a role for interrupting passage of leakage flux. The filling member 4 plays a role for reducing windage loss of the rotor 1 during rotation.

Description

  The present invention relates to a rotating electrical machine having a rotor, such as an electric motor and a generator, and more particularly to a permanent magnet embedded rotating electrical machine in which a permanent magnet is embedded in a rotor.

  FIG. 6 is a cross-sectional view showing a configuration of one pole of the stator 11 and the rotor 1c of this type of permanent magnet embedded rotary electric machine. In this permanent magnet-embedded rotating electric machine, two slots 2 are formed in the rotor core 5c of the rotor 1c to form one pole, and two permanent magnets are formed in the two slots 2. 3 is embedded. Here, between the two slots 2 in one pole, there is a center bridge 9 which is a thin portion of the rotor core 5c, and the end of the two slots 2 opposite to the center bridge 9 and the rotor core. Between the outer periphery of 5c, there is a side bridge 14 which is the same thin portion of the rotor core 5c. In the rotor core 5 c, the inner peripheral area of the slot 2 and the outer peripheral area of the slot 2 are connected via a center bridge 9 and a side bridge 14.

  The stator 11 has a hollow cylindrical stator core 12. The rotor 1 c is inserted inside the stator core 12. The stator core 12 is provided with a plurality of slots along the circumferential direction, and a stator coil 13 is wound in these slots.

  The magnetic flux generated from the permanent magnet 3 of the rotor core 5 c flows to the permanent magnet 3 having a different polarity via the stator core 12. However, a part of the magnetic flux generated from the permanent magnet 3 flows through the center bridge 9 and the side bridge 14 without passing through the stator core 12 and causes a short circuit state of the magnetic flux. In general, this short-circuited magnetic flux is called leakage magnetic flux. Generation | occurrence | production of this leakage magnetic flux causes the fall of the output torque of a permanent magnet embedding type rotary electric machine.

  In order to suppress the leakage magnetic flux, it is desirable to make the center bridge 9 and the side bridge 14 as thin as possible. However, if the center bridge 9 and the side bridge 14 are made thinner, the resistance to centrifugal force generated during the rotation of the rotor 1c is reduced. Therefore, it is necessary to design the thickness of the center bridge 9 and the side bridge 14 according to the rotational speed of the rotor 1c. However, as long as the center bridge 9 and the side bridge 14 are provided, the leakage magnetic flux cannot be made zero.

  As a document disclosing a technique for solving this problem, there is Patent Document 1. FIG. 7 is a cross-sectional view showing the configuration of the rotor 1d of the permanent magnet embedded rotary electric machine disclosed in Patent Document 1. As shown in FIG. In FIG. 7, parts corresponding to those in FIG. 6 are given the same reference numerals and explanations thereof are omitted. The rotor core 5d of the rotor 1d does not have the one corresponding to the side bridge 14 in FIG. The rotor core 5d is formed with a notch 10 that communicates the slot 2 with the outer periphery of the rotor core 5d. The notch 10 has the same permanent magnetic flux generated from, for example, the N pole of the permanent magnet 3 in the slot 2 via a closed magnetic path in the rotor core 5d that does not pass through the stator core (not shown). It functions as a flux barrier that prevents the magnetic flux leaking to, for example, the south pole of the magnet 3. According to the rotor 1d, since the notch 10 is provided, the leakage magnetic flux can be made substantially zero. Therefore, the permanent magnet embedded rotary electric machine having the rotor 1c with the side bridge 14 of FIG. The magnet torque can be increased compared to

JP2013-46421A

J. et al. E. Vraccik, “Predictin® software winders in alternator”, NASA Technical Net D-4849 (1968)

  By the way, since the rotor core 5d shown in FIG. 7 has the notch part 10, the wind loss which is energy lost by air resistance at the time of rotation is large compared with the rotor core 5c shown in FIG. Further, in the rotor core 5d shown in FIG. 7, when the permanent magnet 3 is broken during the rotation, the permanent magnet 3 is scattered from the slot 2 to the outside of the rotor 1d through the notch 10, and the stator core There is a possibility of contact. In the rotor core 5d shown in FIG. 7, the permanent magnet 3 in the slot 2 is movable in the direction of the rotation axis of the rotor core 5d. For this reason, it is necessary to provide end plates for preventing the permanent magnet 3 from falling off at both ends of the rotor core 5d in the rotation axis direction.

  FIG. 8 is a side view showing a configuration example of a rotor 1d having such an end plate 7. As shown in FIG. In FIG. 8, a shaft 8 that is a rotation shaft passes through the rotor core 5d, and two end plates 7 are fixed to both ends of the rotor core 5d in the rotation axis direction. Thus, the conventional permanent magnet embedded rotary electric machine needs to provide the end plates 7 at both ends in the axial direction of the rotating shaft of the rotor core 5d in order to prevent the permanent magnet 3 from falling off. There was a problem that caused an up.

  The present invention has been made in view of the circumstances described above, and a first object of the invention is to reduce the windage loss of the rotor in a permanent magnet embedded rotary electric machine including a rotor that excludes a side bridge. This is to prevent the output torque from being lowered. A second object of the present invention is to eliminate the need for an end plate for preventing the permanent magnet from falling off the rotor in the permanent magnet embedded type rotating electrical machine.

  In the present invention, two slots per pole are formed in the circumferential direction of the rotor, and two slots are embedded in each slot, and permanent magnets are embedded in each slot. A slot having a notch for communicating the end on the side of the adjacent pole with the outer periphery of the rotor, and the notch is filled with a replenishing member made of a non-magnetic material. A magnet embedded rotary electric machine is provided.

  In a preferred embodiment, the replenishing member fixes the permanent magnet in the slot, and prevents the permanent magnet from falling off the slot in the direction of the rotation axis.

  According to the present invention, the portion where the slot communicates with the outer periphery of the rotor is filled with the supplementary member made of a non-magnetic material, thereby reducing the windage loss of the rotor and lowering the output torque of the permanent magnet embedded rotary electric machine. Can be prevented. In the present invention, when the replenishing member fixes the permanent magnet in the slot and prevents the permanent magnet from falling off the slot in the direction of the rotation axis, an end plate for preventing the permanent magnet from falling off is unnecessary. There is an advantage to become.

It is sectional drawing which shows the structure of the rotor of the permanent magnet type electric motor which is 1st Embodiment of this invention. It is sectional drawing of a salient pole type | mold rotor. It is a perspective view of a salient pole type rotor. It is the graph which showed the calculation result of the windage loss about a perfect circle rotor and a salient pole type rotor. It is sectional drawing which shows the structure of the rotor of the permanent magnet type electric motor which is 2nd Embodiment of this invention. It is sectional drawing which shows the structure for 1 pole of the stator and rotor of the conventional permanent magnet embedding type rotary electric machine. It is sectional drawing which shows the structure of the rotor of the permanent magnet embedding type rotary electric machine which excluded the conventional side bridge. It is a side view which shows the structure of the same rotor.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is a cross-sectional view showing a configuration of a rotor 1 of a permanent magnet embedded rotary electric machine according to a first embodiment of the present invention. In FIG. 1, parts corresponding to those in FIGS. 6 and 7 are given the same reference numerals. In FIG. 1, the shaft 8 is not shown.

  The rotor 1 has a rotor core 5. The rotor core 5 is formed by laminating silicon steel plates. The rotor core 5 may be configured by cutting a simple iron block. In the rotor core 5, two slots 2 per pole penetrate in the direction of the rotation axis, and two permanent magnets 3 are embedded in the two slots 2. Two permanent magnets 3 embedded in two slots 2 for one pole have magnetic poles of the same polarity facing a stator core (not shown). In addition, between the adjacent poles of the rotor core 5, the two permanent magnets 3 on one pole and the two permanent magnets 3 on the other pole have different magnetic poles between the poles. ). The permanent magnet 3 is preferably a neodymium magnet or a ferrite magnet, but is not necessarily limited thereto. In the rotor core 5 shown in FIG. 1, eight poles are formed by the 16 slots 2, but the number of poles formed in the rotor core 5 is not limited to eight. Further, the way of winding the coil around the stator is roughly classified into concentrated winding and distributed winding, but either winding method may be used. In FIG. 1, two slots 2 for one pole are arranged so as to form a V shape when the central axis of the rotor 1 is viewed downward, but two slots for one pole are arranged. The slots 2 may be arranged in a single letter shape or in an inverted V shape.

  In the rotor core 5, there is a center bridge 9 that is a thin portion of the rotor core 5 between the two slots 2 for one pole. Further, on the opposite side of the two slots 2 in one pole to the center bridge 9, a notch portion 10 is formed that communicates the slot 2 with the outer periphery of the rotor core 5. This notch 10 functions as a flux barrier that prevents passage of leakage magnetic flux. The notch 10 is filled with the replenishing member 4. The replenishing member 4 plays a role of reducing windage loss when the rotor core 5 rotates. The replenishing member 4 is a resin made of a nonmagnetic material. The reason why the replenishing member 4 is made of a nonmagnetic material is that the function of the notch 10 as a flux barrier is not impaired. In a preferred embodiment, the replenishing member 4 is filled so that the cross section of the rotor core 5 in the filled state forms a perfect circle with no irregularities. However, the cross section of the rotor core 5 filled with the replenishing member 4 is not necessarily a perfect circle, and the difference in unevenness of the outer peripheral surface of the rotor core 5 that causes the windage loss is reduced. do it.

In the present embodiment, the torque T shown in the following equation is generated in the rotor 1 of the permanent magnet embedded rotary electric machine.
T = Pn × Ψm × iq + Pn × (Ld−Lq) × id × iq (1)
In the above formula (1), Pn is the number of pole pairs of the rotor 1, Ψm is a magnetic flux interlinked with the stator coil among the magnetic flux generated by the permanent magnet 3, id is a d-axis current flowing through the stator coil, iq Is a q-axis current flowing in the stator coil, Ld is a d-axis inductance, and Lq is a q-axis inductance. The first term on the right side of the above formula (1) is the magnet torque, and the second term on the right side is the reluctance torque.

Here, the relationship between the magnetic flux Ψm and the induced voltage Vemf is as follows.
Ψm = Vemf / (2πf) (2)

In the above formula (2), f is the frequency of the current flowing through the stator coil, and Vemf is the induced voltage at the same frequency f.

  From the above formulas (1) and (2), when the same magnet torque is obtained, the q-axis current iq can be reduced as the magnetic flux Ψm increases. When the flux barrier is provided by removing the side bridge from the rotor 1 as in the present embodiment, the magnetic flux Ψm can be increased by reducing the leakage magnetic flux by the action of the flux barrier. For this reason, according to the present embodiment, the q-axis current iq can be reduced as compared with the case where the side bridge 14 is provided as shown in FIG.

  Moreover, in this embodiment, the replenishment member 4 with which the notch part 10 as a flux barrier was filled brings about the effect which reduces a windage loss. In order to facilitate understanding of this effect, a reference example is shown below. Non-Patent Document 1 describes the windage loss that occurs in the salient pole rotor 1a as exemplified in FIGS. 2 is a cross-sectional view of the salient pole type rotor 1a, and FIG. 3 is a perspective view of the salient pole type rotor 1a. Slots and magnets are not shown.

According to Non-Patent Document 1, the increment ratio K of the windage loss generated in the salient pole rotor 1a to the windage loss generated in the perfect circle rotor can be expressed by the following equation.
K = 8.5 (H / R) +2.2 (3)
In the above formula (3), R is the rotor radius that is the length from the rotation axis center 15a to the outer periphery of the salient pole type rotor core 5a including the salient pole part 16a, and H is the radial length of the salient pole part 16a. That's it. However, H / R> 0.06.

  FIG. 4 is a graph showing the calculation results of windage loss for the perfect circle rotor and the salient pole type rotor 1a. In FIG. 4, the calculation was performed with the rotor radius R being 100 mm, the rotor axial length being 100 mm, and the salient pole radial length H being 10 mm. However, values of a temperature of 25 ° C. were used for the air density and the kinematic viscosity coefficient. In this case, H / R = 0.1, and if H / R = 0.1 is substituted into the above equation (3), K = 3.05. Therefore, in this case, the windage loss of the salient pole type rotor 1a with respect to the perfect circle rotor is 3.05 times. In FIG. 4, when the perfect circle rotor and the salient pole type rotor 1a are rotated at a rotational speed of 12000 r / min, for example, the wind loss generated in the true circle rotor is 500 W, whereas the salient pole type rotation is performed. The windage loss generated in the child 1a is 1521W. The same applies to the rotor 1d from which the side bridge 14 as shown in FIG. 7 is eliminated, and the windage loss is very large as compared to a perfect circle rotor.

  In this embodiment, by filling the notch 10 with the replenishing member 4, the windage loss of the rotor 1 can be reduced to the same windage loss as that of the perfect circle rotor. If the replenishing member 4 is overfilled or underfilled, the outer peripheral surface of the rotor 1 is uneven. Even in such a case, the refilling member 4 is not filled at all with the rotor 1d shown in FIG. The windage loss of the rotor 1 is reduced compared to.

  Moreover, according to this embodiment, since the replenishment member 4 was filled in the notch part 10 of the rotor core 5, there exists another effect. First, since the replenishing member 4 is filled in the notch portion 10, even if the permanent magnet 3 in the slot 2 is damaged during the rotation of the rotor 1, the permanent magnet 3 is scattered outside the rotor 1. It is possible to prevent the permanent magnet 3 from coming into contact with the stator core.

  Moreover, the permanent magnet 3 becomes difficult to rust by filling the notch 10 with the replenishing member 4. Since the permanent magnet 3 often uses an iron-based material, if the permanent magnet 3 is exposed to the air, oxygen in the air is bound to iron of the permanent magnet 3 and rust is likely to occur. However, if the replenishing member 4 is filled in the cutout portion 10, the permanent magnet 3 is less likely to come into contact with air, and the permanent magnet 3 becomes difficult to rust.

  Further, the filling of the replenishing member 4 makes it possible to balance the rotor 1 in the direction of the rotation axis. More specifically, if the rotation axis of the rotor 1 and the center axis of the shaft are offset and fitted in the interference fitting process of the rotor 1 and the shaft, the weight balance of the rotor core 5 with respect to the rotation axis is uneven. It becomes. Under the prior art, in such a case, the balance is made uniform by adjusting the weights of the end plates 7 (see FIG. 8) provided at both ends of the rotor 1 in the axial direction. However, in the present embodiment, it is possible to cut a part of the replenishing member 4 of the rotor 1 or to adjust the filling amount of the replenishing member 4 into the notch 10. Thus, by adjusting the balance by the amount of the replenishing member 4, the rotor 1 of the permanent magnet embedded rotary electric machine can be easily balanced.

  In this embodiment, the replenishing member 4 filled in the notch 10 fixes the permanent magnet 3 in the slot 2, so that the permanent magnet 3 moves in the direction of the rotation axis and falls off the rotor core 5. Can be prevented. Therefore, in this embodiment, it is not necessary to provide the rotor 1 with the end plate 7 as shown in FIG. 8 in order to prevent the permanent magnet 3 from falling off. Therefore, according to this embodiment, the manufacturing cost of the rotor 1 can be reduced by the amount of the end plate 7.

Second Embodiment
FIG. 5 is a cross-sectional view showing a configuration of a rotor 1b of a permanent magnet embedded rotary electric machine according to a second embodiment of the present invention. In FIG. 5, parts corresponding to those shown in FIG. 1 are given the same reference numerals, and explanation thereof is omitted.

  The rotor 1b in the present embodiment has a configuration in which a ring 6 is added to the outer peripheral side of the rotor 1 in the first embodiment (FIG. 1). The ring 6 has a hollow cylindrical shape, and has an inner diameter that substantially matches the outer diameter of the rotor core 5. The ring 6 has its inner periphery in contact with the outer periphery of the rotor core 5 and covers the rotor core 5.

  According to the present embodiment, as in the first embodiment, the notch 10 that communicates the slot 2 with the outer periphery of the rotor core 5 is filled with the replenishment member 4 made of a nonmagnetic material. The same effect can be obtained. Further, according to the present embodiment, since the outer periphery of the rotor core 5 is further covered by the ring 6, the unevenness on the outer peripheral surface of the rotor 1 is further reduced and windage loss is reduced as compared with the first embodiment. Can be made closer to the windage loss of a perfect circular rotor.

  Although the first and second embodiments of the present invention have been described above, other embodiments are conceivable for the present invention. For example:

  In the first embodiment, the notch 10 is filled with the replenishing member 4 so that the cross section of the rotor 1 becomes a perfect circle, but the amount of the cross section of the rotor 1 becomes a perfect circle. A small amount of the replenishment member 4 may be filled in the notch 10, or a larger amount of the replenishment member 4 may be filled in the notch 10. Also in this aspect, the windage loss can be reduced and the output torque of the permanent magnet embedded rotary electric machine can be increased as compared with the conventional rotor 1c in which the replenishment member 4 is not filled at all.

1, 1b, 1c, 1d ... Rotor, 1a ... Salient pole type rotor, 2 ... Slot, 3 ... Permanent magnet, 4 ... Replenishing member, 5, 5b, 5c, 5d ... Rotor core 5a ... salient pole type rotor core, 6 ... ring, 7 ... end plate, 8 ... shaft, 9 ... center bridge, 10 ... notch, 11 ... stator, 12 ... fixed Child core, 13 ... Coil, 14 ... Side bridge, 15a ... Center of rotation axis, 16a ... Salient pole, R ... Rotor radius, H ... Radial length of salient pole, K ... Wind Loss increment percentage.

Claims (3)

Two slots per pole are formed in the circumferential direction of the rotor, and two slots per pole are formed in the circumferential direction, and permanent magnets are embedded in each slot.
The rotor has a notch for communicating the end of the adjacent pole in two slots of each pole with the outer periphery of the rotor, and a replenishing member made of a nonmagnetic material is provided in the notch. A permanent magnet embedded rotary electric machine characterized by being filled.   2. The permanent magnet embedded rotating electric machine according to claim 1, further comprising a ring made of a nonmagnetic material having an inner periphery in contact with an outer periphery of the rotor. 3. The permanent magnet embedded rotation according to claim 1, wherein the replenishing member fixes the permanent magnet in the slot and prevents the permanent magnet from falling off from the slot in the rotation axis direction. Electric.

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