JP3832530B2 - Permanent magnet motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inner rotor type permanent magnet motor used in the compressor or the like, in particular detail, it relates to adaptive motor can be obtained a permanent magnet motor rotor structure.
[0002]
[Prior art]
The inner rotor configuration of this type of permanent magnet motor has a permanent magnet embedded in the rotor core, and for example, those shown in FIGS. 7 and 8 have been proposed. As shown in FIG. 7, on the rotor core 2 in the 24-slot stator core 1, plate-like permanent magnets 3 are arranged in the circumferential direction along the outer diameter for the number of poles (for example, four poles) of the permanent magnet motor. In addition, a flux barrier 4 is formed between the adjacent permanent magnets 3 to prevent magnetic flux short circuit and leakage. In addition, 5 is a center hole (hole for shafts).
[0003]
Here, assuming that the magnetic flux distribution in the gap (between the teeth of the stator core 1 and the permanent magnet 3) by the permanent magnet 3 is sinusoidal, the torque T of the permanent magnet motor is T = Pn {Φa · Ia Cos β-0.5 (Ld−Lq) · I ² · sin 2β} T is the output torque, Φa is the armature flux linkage by the permanent magnets on the d and q coordinate axes, Ld and Lq are d and q axis inductances, Ia is the amplitude of the armature current on the d and q coordinate axes, and β is The advance angle of the armature current on the d and q coordinate axes from the q axis, Pn, is the number of pole pairs.
[0004]
In the above formula, the first term is the magnet torque generated by the permanent magnet 3, and the second two terms are the reluctance torque generated by the difference between the d-axis inductance and the q- axis inductance. For details, see T.W. IEEE Japan, Vol. See 117-D, No. 7, 1997. Further, the rotor core 2 shown in FIG. 8 has a configuration having a permanent magnet 6 having a shape different from that of the permanent magnet 3 shown in FIG. 7, but the application of the above formula is clear.
[0005]
By the way, typical permanent magnets 3 and 6 include an inexpensive ferrite magnet and an expensive rare earth magnet. When a ferrite magnet is used, it is possible to obtain permanent magnets of various shapes due to the ease of molding, but it is difficult to reduce the size of the rotor core because the magnetic flux density is small. On the other hand, when a rare earth magnet is used, the magnetic flux density is large, so that the rotor core can be easily reduced in size. However, the shape of the permanent magnet is limited due to difficulty in forming. Therefore, either a ferrite magnet or a rare earth magnet has been selected in consideration of the application and cost of the motor.
[0006]
[Problems to be solved by the invention]
However, in the permanent magnet motor, as shown in FIGS. 7 and 8, only one type (for example, one of a rare earth magnet or a ferrite magnet) is used as the permanent magnet constituting the magnetic pole (four poles). There were the following drawbacks.
[0007]
For example, when a permanent magnet of a magnetic pole is composed only of ferrite magnets, the amount of magnets must be increased to increase the magnetic flux density (the magnetization width must be increased), and as a result, most of the rotor core is Thus, the q-axis inductance is small, the difference between the q-axis and the d-axis inductance (reluctance torque parameter; see the above equation) is small, and sufficient reluctance torque cannot be obtained. Also, when the permanent magnet of the magnetic pole is composed of only rare earth magnets, the magnetic flux density is high, so it does not occupy most of the rotor core as in the case of a ferrite magnet, but the magnetic flux density may be too high, Moreover, since it is expensive as mentioned above, the cost of a motor will become high. As described above, it is difficult to obtain a desired reluctance torque and magnetic flux density, that is, it is difficult to obtain a low-cost one corresponding to a narrow selection range and an appropriate motor.
[0008]
The present invention has been made in view of the above-mentioned problems, and its object is to expand the selection range of the reluctance torque and magnetic flux density and to reduce the cost, and to obtain an adaptive motor. It is to provide an electric motor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a permanent magnet motor in which a magnet-embedded field core (rotor core) is arranged in a stator core, wherein the magnet constituting the magnetic pole of the field of the permanent magnet motor is a magnet. And a first permanent magnet arranged in a number corresponding to the number of poles in the circumferential direction along the circumference of the rotor core inner diameter, and a second permanent magnet arranged along the boundary of the magnetic poles of the first permanent magnet. The second permanent magnet is shared by adjacent magnetic poles, each magnetic pole is composed of at least three permanent magnets, the first permanent magnet is composed of a rare earth magnet, and the second permanent magnet is composed of a ferrite magnet. It is a feature.
[0010]
In the present invention, the second permanent magnet may include two permanent magnets having a rectangular cross section arranged parallel to each other along the boundary of the magnetic pole.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. In the permanent magnet motor according to the present invention, if a plurality of permanent magnets for each magnetic pole are formed of different materials, various reluctance torques and magnetic flux densities can be selected, and the cost can be reduced. This is because it does not interfere with the rotation of the motor.
[0012]
Therefore, as shown in FIG. 1 and FIG. 2, the rotor core 10 of this permanent magnet electric motor is composed of a rare earth magnet permanent magnet 11 and a ferrite magnet permanent magnet 12 for each magnetic pole, and the permanent magnet 12 is an adjacent magnetic pole. Sharing. Permanent magnets 11 have a rectangular cross section (thin plate shape) and are arranged in a number corresponding to the number of poles (for example, 4 poles) in the circumferential direction along the periphery of the core inner diameter (center hole 14). A rectangular cross section (thick plate shape) is formed on the boundary between the magnetic poles of the permanent magnet 11 and arranged in the outer diameter direction from about 1/3 of the core radius. Therefore, each magnetic pole is composed of three permanent magnets 11 and permanent magnets 12 and 12. Further, a flux barrier hole 13 is provided between both end portions of the permanent magnet 11 and the core inner diameter side end portion of the permanent magnet 12 in order to prevent short-circuiting and leakage of magnetic flux. In addition, 14 is a center hole for shafts, and 15 is a stator core.
[0013]
The reluctance torque and the magnetic flux density will be described with reference to FIG. In the figure, the curve of the broken line arrows represent the magnetic flux. In this case, since the permanent magnet 11 of the rare earth magnet and the shared permanent magnets 12 and 12 are arranged for the adjacent magnetic poles for each magnetic pole, the magnetic flux density can be increased, and the breakage of FIG. As shown in the line frame A, it is possible to take a wider area on the core outer diameter side of each magnetic pole. Therefore, taking a wide broken line frame A illustrated in FIG. 3, i.e. reducing the percentage of the magnet, since it is possible to increase the proportion of core made of magnetic steel, q-axis inductance made large as compared with the d-axis inductance The difference between the q-axis and d-axis inductance (reluctance torque parameter) increases, and the reluctance torque increases.
[0014]
In addition, the combined use of ferrite magnets and rare earth magnets reduces the magnetic flux density. For example, the magnetic flux density is lower than when all of the magnets are composed of rare earth magnets. That is, the magnetic flux density is not too high, and an appropriate magnetic flux density is selected. be able to. Moreover, for example, when all of the magnets are composed of ferrite magnets, the thickness (magnetization width) of the permanent magnets may exceed the manufacturing limit if an attempt is made to obtain the required magnetic flux density. In combination, the magnetic flux density can be adjusted, that is, a desired magnetic flux density can be easily obtained by a method other than the magnetization width. In addition, since the flux barrier hole 13 provided between the permanent magnet 11 and the permanent magnet 12 can prevent a short circuit and leakage of the magnetic flux, the magnetic flux error due to the permanent magnet 11 is particularly small, that is, necessary. The magnetic flux density can be obtained more easily.
[0015]
In this way, the magnetic flux density can be increased or decreased by the rare-earth magnet permanent magnet 11 and the magnetic flux density can be finely adjusted by the ferrite magnet permanent magnet 12, that is, the optimum magnetic flux density can be easily obtained. Can do. In addition, by using an inexpensive ferrite magnet in combination, the amount of rare earth magnet used can be reduced. For example, it is possible to reduce the cost compared to the case where all the magnetic poles are composed of rare earth magnets, and the cost can be reduced. For the reasons described above, the reluctance torque and magnetic flux density can be selected from a wider range of freedom (degree of freedom), so that an adaptive motor can be easily obtained.
[0016]
As shown in FIG. 2, the rotor core 10 is obtained by punching a magnetic steel sheet with a press and automatically laminating it in a mold, and embedding the permanent magnets 11 and 12 to magnetize them. At least the shape holes of the permanent magnets 11 and 12 are formed in advance. At the same time, a hole 13 for the flux barrier may be formed. Therefore, it is not different from the conventional manufacturing process, that is, the cost is not different from the conventional manufacturing process, and the cost is not increased. Further, the fat Rashiresu DC motor incorporating a rotor core formed by the above, by using as a compressor motor or the like of the air conditioner, without up the cost, increase the performance up (operation efficiency of the air conditioner, the vibration And noise reduction).
[0017]
At least the shape hole of the permanent magnet 11 and the hole 13 for the flux barrier may be integrated, that is, connected holes. Moreover, sufficient intensity | strength is given so that the location by the side of the core outer diameter of the permanent magnet 12 can endure centrifugal force. Furthermore, since the stator core 15 may be the same as that in FIGS. 7 and 8, the description thereof is omitted.
[0018]
FIG. 4 shows a modification of the above embodiment. In the figure, the same parts as those in FIG. The rotor core 10 of this permanent magnet motor is formed by dividing the permanent magnet 12 of the above-described embodiment into two, that is, permanent magnets 16a and 16b of ferrite permanent magnets having a rectangular cross section (thin plate shape thinner than the previous example). They are arranged in one-third to or al outer diameter direction of the core inner diameter along the pole boundary. Therefore, each magnetic pole is composed of three permanent magnets 11 and permanent magnets 16a and 16b.
[0019]
In this case, the magnetization width of the permanent magnets 16a and 16b is smaller than that of the previous embodiment (see FIG. 3). For example, the permanent magnets 16a and 16b are longer than the permanent magnet 12 and the magnetization width of the permanent magnet 11 of a rare earth magnet. Is made larger than that in FIG. 3, the magnetic flux density can be made comparable to that in FIG. 3.
Therefore, no change from the previous SL embodiment for the magnetic flux density, also possible without the magnet occupancy of the core increases, i.e. since it is possible to widen the area without the permanent magnets in the same manner as FIG. 3, compared with the d-axis inductance As a result, the q-axis inductance is increased, the difference between the q-axis and the d-axis inductance is increased, and the reluctance torque is increased. Moreover, since the burden in the location between the core outer-diameter side edge part of permanent magnet 16a, 16b and a core outer diameter becomes light, the intensity | strength of the location comes to fully endure centrifugal force.
[0020]
FIG. 5 shows a modification of the rotor core of the present invention. In the figure, the same parts as those in FIG. In the rotor core 10 of this permanent magnet motor, the ferrite magnet and the rare earth magnet of the embodiment shown in FIG. 3 are reversed , that is, a permanent magnet 17 of a ferrite magnet is disposed in place of the permanent magnet 11, and the permanent magnet 12 is replaced. A permanent magnet 18 of rare earth magnet is arranged.
[0021]
Permanent magnets 17 have a polygonal cross section (for example, a deformed hexagon) and are arranged in a number corresponding to the number of poles in the circumferential direction along the circumference of the core inner diameter. The permanent magnet 17 is longer than the permanent magnet 18 and has a larger magnetization width to compensate for the magnetic flux density. The permanent magnet 18 has a rectangular cross section (thick plate shape) and is arranged on the boundary of the magnetic poles by the permanent magnet 17 in the outer diameter direction from about 2/3 of the core radius. Although this permanent magnet 18 is smaller than the permanent magnet 12, it is a rare earth magnet, and therefore generates a magnetic flux density that is the same as that of the permanent magnet 12.
[0022]
Therefore, in the rotor core 10 of this modified example, the previous SL embodiment it is expected to generate almost the same magnetic flux density, also possible without the magnet occupancy of the core is so raised, that the 3 same Since a region without permanent magnets can be made as wide as possible, the q-axis inductance can be larger than the d-axis inductance, the difference between the q-axis and the d-axis inductance is increased, and the reluctance torque is increased. A flux barrier may be provided on the end portion side of the permanent magnet 18, but if the end portion on the core outer diameter side of the permanent magnet 18 is made as close as possible to the outer diameter of the core, the flux barrier is not provided. That's it.
[0023]
FIG. 6 shows a modification of the embodiment shown in FIG. In the figure, the same parts as those in FIG. The rotor core 10 of this permanent magnet motor has a shape in which the permanent magnet 18 is divided into two parts, that is, permanent magnets 19a and 19b of a rare earth permanent magnet having a rectangular cross section (thin plate shape) along the magnetic pole boundary. 2/3 are arranged in much the al outer radial. Therefore, each magnetic pole is composed of three permanent magnets 17 and permanent magnets 19a and 19b.
[0024]
In this case, the permanent magnets 19a, although 19b of magnetization width is slightly smaller than the previous SL embodiment (see FIG. 5), for example, a permanent magnet 19a, 19b and the large (long in the radial direction), and the ferrite magnet permanent If the magnetized width of the magnet 17 is made smaller than that shown in FIG. 5, the magnetic flux density can be set to the same level as in FIG. Therefore, no change from the previous SL embodiment for the magnetic flux density, also even if the magnet occupancy of the core is increased, without down, i.e. it can take a wide area without the permanent magnets similar to FIG. 3 Therefore, the q-axis inductance is larger than the d-axis inductance, the difference between the q-axis and the d-axis inductance is increased, and the reluctance torque is increased. A flux barrier may be provided on the end side of the permanent magnets 19a and 19b. However, if the end portions on the core outer diameter side of the permanent magnets 19a and 19b are very close to the outer diameter of the core, the flux barrier is provided. Therefore, the core strength of the end portion on the outer diameter side of the core can be further maintained.
[0025]
As described above, various reluctance torques and magnetic flux densities can be selected by combining various ferrite magnets and rare earth magnets, that is, their selectivity can be expanded. It is obvious that the embodiment shown in FIGS. 4 to 6 has the same effect as the embodiment shown in FIGS.
[0026]
【The invention's effect】
As described above , according to the present invention, in a permanent magnet motor in which a magnet-embedded field core (rotor core) is disposed in a stator core, the magnet constituting the magnetic pole of the field of the permanent magnet motor And a first permanent magnet arranged in a number corresponding to the number of poles in the circumferential direction along the circumference of the rotor core inner diameter, and a second permanent magnet arranged along the boundary of the magnetic poles of the first permanent magnet. The second permanent magnet is shared by adjacent magnetic poles, each magnetic pole is composed of at least three permanent magnets, the first permanent magnet is composed of a rare earth magnet, and the second permanent magnet is composed of a ferrite magnet. by the wider range without the magnet as the core outer diameter side of each magnetic pole, increasing the difference between the q-axis and d-axis inductance by increasing the q-axis inductance as compared to the d-axis inductance, Mari, it is possible to increase the reluctance torque. Moreover, since the magnetic flux density of the ferrite magnet is low, the magnetic flux density can be adjusted in combination with the rare earth magnet to obtain an appropriate magnetic flux density to facilitate obtaining a desired magnetic flux density, that is, reluctance torque and magnetic flux density. Can be expanded, and the selection range of magnetic flux density can be expanded. In addition, by using an inexpensive ferrite magnet in combination, the cost can be reduced, and as a result, an adaptive motor can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a permanent magnet motor showing an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view of a rotor of the permanent magnet motor shown in FIG.
3 is a schematic enlarged plan view of a rotor of the permanent magnet motor shown in FIG. 1. FIG.
4 is a schematic plan view for explaining a modification of the rotor of the permanent magnet motor shown in FIG. 1; FIG.
FIG. 5 is a schematic plan view for explaining a modification of the rotor of the permanent magnet motor shown in FIG. 1;
6 is a schematic plan view for explaining a modified example of the rotor of the permanent magnet motor shown in FIG. 1; FIG.
FIG. 7 is a schematic plan view of a conventional permanent magnet motor.
FIG. 8 is a schematic plan view of a conventional permanent magnet motor.
[Explanation of symbols]
10 Rotor core (embedded magnet field core)
11, 18, 19a, 19b Permanent magnet (rare earth magnet)
12, 16a, 16b, 17 Permanent magnet (ferrite magnet)
13 holes (for flux barrier)
14 Center hole (for shaft)
15 Stator core

Claims (2)

In a permanent magnet motor in which a magnet-embedded field core (rotor core) is disposed in a stator core,
The magnets constituting the magnetic poles of the field of the permanent magnet motor include first permanent magnets arranged in a number corresponding to the number of poles in the circumferential direction along the circumference of the inner diameter of the rotor core, and magnetic poles formed by the first permanent magnets. A second permanent magnet disposed along the boundary of the second permanent magnet, wherein the second permanent magnet is shared by adjacent magnetic poles, each magnetic pole is composed of at least three permanent magnets, and the first permanent magnet is a rare earth magnet. And the second permanent magnet is a ferrite magnet . The permanent magnet motor according to claim 1, wherein the second permanent magnet includes two permanent magnets having a rectangular cross section arranged parallel to each other along a boundary of the magnetic poles.

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