JP4084889B2 - Permanent magnet motor rotor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet type synchronous motor having a field of a permanent magnet (hereinafter referred to as a magnet) typified by an electric motor for driving a compressor of a refrigerator or an air conditioner, and in particular, in the iron core of a rotor. The present invention relates to a rotor having a so-called embedded magnet structure in which a magnet is embedded.
[0002]
[Prior art]
As the rotor, one having the structure shown in FIG. 5 is known, and disclosed in, for example, Japanese Patent Laid-Open No. 9-182332.
[0003]
FIG. 5 is a plan sectional view showing a section perpendicular to the axial direction of the rotor. In FIG. 5, reference numeral 1a denotes an iron core, and a thin iron plate having a shaft hole 10 and a plurality of receiving holes 3a for inserting magnets. Are stacked in the axial direction. A flat magnet 2a is inserted in the housing hole 3a in the axial direction, and one magnet 2a is magnetized so as to form one pole, and forms a four-pole field in the illustrated example. It is like that. As the magnet material, rare earth magnets are mainly used.
[0004]
A gap portion 4a is formed at both ends of the accommodation hole 3a toward the outer periphery so as to prevent magnetic flux (hereinafter referred to as main magnetic flux) from the magnet from being short-circuited and leaked between adjacent poles. And between this space | gap part 4a and a rotor outer peripheral part, the bridge | bridging part 5a which narrowed the width as much as possible is formed.
[0005]
In the case of a rotor having such a configuration, a large q-axis inductance can be obtained because there are many iron core portions on the outer peripheral portion of the rotor. Therefore, in addition to the main magnetic flux torque obtained by the current of the energization winding of the motor stator and the main magnetic flux linked to this, it has the feature that the reluctance torque obtained by the difference in the magnetic resistance depending on the rotor position can be greatly utilized. ing.
[0006]
In general, the torque T of an electric motor is as follows: T1 is a main magnetic flux torque and T2 is a reluctance torque.
T = T1 + T2 (1)
The direction connecting the magnetic pole center of the magnet and the rotation axis is the d axis, the phase of the electrical angle with respect to the d axis is the q axis, the main magnetic flux amount is Φ, the d axis current is Id, Is Iq, d-axis inductance is Ld, and q-axis inductance is Lq,
T1 = Φ · Iq (2)
T2 = (Ld−Lq) Id · Iq (3)
It is represented by In the equation (3), if the control is performed so that Id becomes a negative value, the reluctance torque T2 can be increased as Lq becomes larger than Ld.
[0007]
FIG. 6 shows another example of the rotor, in which a flat plate is formed in a substantially V-shaped accommodation hole 3b formed so as to protrude toward the axial center and have an end portion close to the outer periphery of the rotor. Two magnets 2b are inserted to form a field of each pole. As a magnet material, a ferrite magnet is mainly used, but a rare earth magnet or the like may be used. As in the example of FIG. 5, in order to prevent a short circuit of the main magnetic flux, the width of the bridge portion 5b is preferably as narrow as possible, and a gap is provided between the magnet 2b and the bridge portion 5b at both ends of the accommodation hole 3b as necessary. You may comprise so that a part may be formed. Such a rotor is disclosed, for example, in JP-A-9-308148.
[0008]
Also in the example of FIG. 6, since many iron core portions exist on the outer peripheral portion of the rotor, the q-axis inductance Lq is increased, and the reluctance torque can be increased. In addition to this, the magnet housing hole is formed to have a convex shape toward the axial center, as disclosed in, for example, Japanese Patent Application Laid-Open No. 6-339241, and the like. There is a rotor using a magnet, and in this case, the same effect as in the examples of FIGS.
[0009]
[Problems to be solved by the invention]
In the conventional rotor, in order to increase the torque of the electric motor as much as possible, the main magnetic flux torque T1 is increased using a high performance magnet such as a rare earth magnet having a large residual magnetic flux density, while the q-axis inductance is increased as much as possible. Thus, a large reluctance torque T2 is extracted. In order to increase the q-axis inductance, for example, in the rotor as shown in FIG. 5, the circumferential width of the gap 4a is formed as narrow as possible, and in the rotor as shown in FIG. In the case where a gap is provided between the poles, only a small gap is provided on the outer peripheral side of the magnet 2b.
[0010]
On the other hand, however, if the gap between the poles is reduced, the main magnetic flux short circuit leakage increases and the main magnetic flux torque may be reduced. Therefore, the balance with the reluctance torque makes designing difficult. In general, an electric motor using reluctance torque is configured such that the air gap between the stator and the rotor is as small as possible. However, in a motor for driving a compressor of 1 to 2 horsepower class, the air is limited due to structural limitations. The gap dimension is relatively large, about 0.5 to 0.7 mm. Accordingly, since the reluctance torque cannot be sufficiently extracted due to an increase in magnetic resistance, the ratio of the reluctance torque T2 to the total torque T is only about 20%, and the total torque T basically accounts for about 80%. A large part is imposed on the magnetic flux torque T1. However, the conventional design products tend to be reluctance torque biased, and even when high performance magnets such as rare earth magnets are used, there is no change in the trend in the configuration.
[0011]
Reducing power consumption for refrigerators and air conditioners is an urgent issue from the standpoint of global environmental conservation, and the motors that drive them are imperative to develop even more efficient ones. ing. The conventional configuration shown in FIGS. 5 and 6 can be said to be a safe configuration as a rotor of a permanent magnet type electric motor that uses both main magnetic flux torque and reluctance torque. The current situation is not necessarily the optimum and ultimate configuration for extracting the maximum capacity of the system.
[0012]
[Means for Solving the Problems]
The present invention includes an iron core and a permanent magnet inserted into a receiving hole for each pole formed in the iron core, and rotates in a state of facing a stator having a slot, and is perpendicular to the axial direction of the iron core. In a cross section, in a rotor of a permanent magnet type electric motor configured such that the interval between the accommodation hole and the outer peripheral portion of the iron core is wide at the center portion of the accommodation hole and narrows at both end portions, Is provided with a gap, and a radial iron core portion having a circumferential width d is left in the gap between adjacent gaps by the gap, and the gap between the gap and the outer circumference of the core is left. In addition, a bridge-shaped iron core portion is left, and the gap portion protrudes toward the pole center to an opening angle θ2 narrower than the opening angle θ1 from the axis of the permanent magnet inserted into the receiving hole. Formed in the circumferential direction of the radial iron core portion. The width d is set to be equal to or larger than the circumferential width of the slot opening of the stator slot.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment of the present invention, a flat plate-shaped permanent magnet or a C-shaped permanent magnet is inserted into the receiving hole, or the receiving hole is formed in a V shape with the convex side facing the axis. Alternatively, a rare earth magnet is used as the permanent magnet, or the gap is filled with a nonmagnetic material.
[0014]
With the above configuration, since the gap extends to a range narrower than the opening angle of the magnet, the area of the gap can be formed large, the short-circuit leakage of the main magnetic flux is reduced, and the main magnetic flux torque of the electric motor is greatly increased. At the same time, the magnetic path of the main magnetic flux is guided toward the pole center, and effectively links with the excitation part of the stator. On the other hand, since the q-axis inductance is maintained in a large state by the radial iron core portion and the bridge-like iron core portion left in the inter-electrode portion, a large reluctance torque can be obtained. As a result, the motor torque, which is the sum of the main magnetic flux torque and the reluctance torque, is greatly improved. When compared with the conventional torque, the current value is reduced and the copper loss is reduced. Increase greatly.
[0015]
【Example】
FIG. 1 is a plan sectional view of an electric motor rotor showing an embodiment of the present invention, and shows a cross section perpendicular to the axial direction of the rotor. The iron core 1 is formed by laminating a large number of thin steel plates of 0.35 mm thickness, 0.50 mm thickness, etc., punched into a predetermined shape by a progressive press die in the axial direction in the press die. The protrusions and recesses are fixed at a plurality of locations by well-known clamping means or the like that are fitted and fixed together in the axial direction. A shaft hole 10 is provided in the center of the substantially cylindrical iron core 1, and a plurality of receiving holes 3 for inserting magnets in parallel with the shaft hole 10 and a plurality of pin holes 6 for inserting caulking pins are provided. Each is provided.
[0016]
The housing hole 3 has a substantially V-shaped cross section for each pole, and is formed so that its end is close to the outer periphery of the rotor with a convex shape toward the axis. The space between the housing hole 3 and the outer periphery of the iron core 1 is configured to be wide at the center of each housing hole and narrow at both ends, and the V-shaped concave portion side of each pole is thicker toward the outer periphery of the rotor. Since the meat core portion is present, the q-axis inductance Lq is large, while the d-axis inductance is small.
[0017]
As shown in FIG. 2, two flat magnets 2 for each V-shape are inserted in the respective receiving holes 3 of the iron core 1 from the axial direction so as to form one pole for each V-shape. Thus, a four-pole field is formed. As a magnet material, a ferrite magnet or a rare earth magnet can be generally used, but the illustrated example shows a shape suitable for a rare earth magnet. That is, the main magnetic flux is made as large as possible by using rare earth magnets such as Nd-Fe-B (neodymium-iron-boron) magnets. In the case of rare earth magnets, those having an arc shape in cross section are expensive and are generally formed in a flat plate shape. Therefore, they are suitable for mounting in a V-shaped accommodation hole as shown in the figure.
[0018]
After the magnet 2 is inserted, end plates 9 are attached to both ends in the axial direction of the iron core 1 to cover them, and the caulking pins 7 are inserted into the pin holes 6 of the iron core and the pin holes 11 of the end plate, respectively. It is to become.
[0019]
Returning to FIG. 1, both end portions of the accommodation hole 3 in the iron core 1 are void portions 4 in which the magnet 2 is not accommodated, and the void portion 4 is bent with respect to the extension line of the cross-sectional contour of the magnet 2. The tip of the magnet 2 is formed so as to project toward the pole center to an opening angle θ2 narrower than the opening angle θ1 from the axis O of the magnet 2. The gap 4 leaves a radial core portion 8 having a width d at the portion between the adjacent poles, and a bridge portion 5 between the outer periphery of the core.
[0020]
Since the gap 4 in the iron core 1 is formed so as to project toward the pole center so that θ2 <θ1, the leakage short circuit of the main magnetic flux between adjacent poles is reduced more than the conventional product, and the main magnetic flux torque component of the motor is reduced. Will increase. In particular, when a high-performance magnet such as a rare magnet is used, the increase in the main magnetic flux torque is significant because the magnetic flux density is high.
[0021]
Further, by forming the relationship θ2 <θ1, there is an effect that the magnetic path of the main magnetic flux can be guided toward the pole center. In other words, since the three-phase 120 ° energization is generally adopted for such energization switching in the stator of the electric motor, the main magnetic flux of each field pole formed in the range of the electrical angle of 180 ° is as narrow as possible. This is because the more concentrated, the greater the contribution to torque. Therefore, also from this point, the main magnetic flux torque can be improved by the presence of the gap 4.
[0022]
On the other hand, the radial iron core portion 8 left in the interpolar portion allows a large amount of stator magnetic flux to flow into and out of the rotor core 1 through this portion, so that the q-axis inductance remains as large as before. The reduction in the reluctance torque of the electric motor due to the gap 4 is maintained low. In this case, the bridge portion 5 acts like a funnel, and has an effect of inducing the flow of the stator magnetic flux into the radial iron core portion 8 or the iron core portion outside the accommodation hole 3.
[0023]
The width of the bridge portion 5 in the radial direction is preferably narrow in view of characteristics, but is determined to be an appropriate width in consideration of the punching technology of the thin iron plate constituting the iron core 1 and the centrifugal strength strength of the bridge portion 5. The And since the iron core 1 is connected by the radial iron core part 8 and the bridge | bridging part 5, each thin iron plate can be punched integrally. However, in the case where the centrifugal strength is insufficient, it is preferable that the caulking pin 7 is inserted into the iron core portion outside the accommodation hole 3 to be reinforced so as to stabilize the quality as shown in the illustrated example. .
[0024]
FIG. 3 shows the change of the main magnetic flux amount Φ and the ratio of the q-axis inductance Lq and the d-axis inductance Ld when the circumferential width d of the radial core portion 8 left in the inter-pole portion is changed. The change of salient pole ratio Lq / Ld is shown, respectively. The main magnetic flux amount Φ can be known by measuring the induced voltage of the stator winding when the rotor is rotated with the rotor facing the stator of the electric motor. On the other hand, the q-axis inductance Lq and the d-axis inductance Ld are similarly known by measuring the maximum value and the minimum value of the winding inductance when the rotor is rotated in a state of facing the stator of the motor. Can do. As described above, the main magnetic flux torque T1 increases as the main magnetic flux amount Φ increases, and the reluctance torque T2 increases as the salient pole ratio Lq / Ld increases.
[0025]
In FIG. 3, a point indicated by P1 represents a point where the width d is equal to the circumferential width of the slot opening of the stator, and the slope of Φ does not change so much at this point, whereas Lq The inclination of / Ld forms a bending point. That is, if the width d is narrower than P1, the magnetic resistance between the stator and the rotor becomes extremely large, which is not preferable because the drop in the reluctance torque exceeds the increase in the main magnetic flux torque. Therefore, by setting the circumferential width d of the radial core portion 8 left in the inter-pole portion to a value not less than the slot opening width P1 and in the vicinity of P1, a high torque electric motor can be obtained.
[0026]
FIG. 4 shows changes in the main magnetic flux amount Φ and changes in the salient pole ratio Lq / Ld when the opening angle θ2 of the gap 4 at both ends of the accommodation hole is changed. It can be seen that the inclination of Lq / Ld does not change much at the point where the opening angle θ2 of the gap 4 becomes equal to the opening angle θ1 of the magnet 2, whereas the inclination of Φ forms a bending point. . That is, when θ2 is made narrower than θ1, the short-circuit leakage of the main magnetic flux Φ between adjacent poles is greatly reduced, and at the same time, the magnetic path of the main magnetic flux is concentrated in the direction of the pole center. It becomes prominent with θ1 as a boundary. Since the increase in the main magnetic flux torque exceeds the decrease in the reluctance torque, a high torque electric motor can be obtained by forming the relationship θ2 <θ1.
[0027]
Note that the tendency shown in FIG. 4 becomes more conspicuous especially when a high-performance magnet such as a rare earth magnet is used, and thus greatly contributes to the improvement of the characteristics of the electric motor. In addition, it is preferable that the opening angle θ2 of the gap portion 4 is small, but it is not preferable to make it too small due to the punching of the iron core 1 or mechanical strength, particularly the strength of the bridge portion 5, and the lower limit value is mainly used. Determined by manufacturing convenience.
[0028]
Further, in the present invention, even when the gaps at both ends of the accommodation hole are filled with a nonmagnetic material such as a resin, the same action is produced, so that the gaps are not necessarily limited to the gaps. Further, the present invention is not limited to a magnet having a V-shaped cross section, and is configured by a single plate-shaped magnet for each pole as shown in FIG. 5 or using a magnet having a C-shaped cross section. Any rotor can be used as long as it is a rotor of a permanent magnet type motor configured such that the distance from the outer peripheral portion of the iron core is wide at the center of each housing hole and narrow at both ends.
[0029]
【The invention's effect】
In the present invention, the viewpoint is changed from the conventional configuration in which the reluctance torque is biased, and the improvement of the main magnetic flux torque is achieved by paying attention to the gap portion between the poles, whereby the main magnetic flux torque and the reluctance torque are The total torque of a certain motor can be greatly increased, which means that the copper loss of the motor can be reduced and the efficiency of the motor can be greatly improved as compared with the conventional torque. In particular, in an electric motor of a type that pursues high torque or high efficiency using a high-performance magnet such as a rare earth magnet, an effective configuration is provided for extracting the maximum capacity of the electric motor.
[Brief description of the drawings]
FIG. 1 is a plan sectional view of a rotor showing an embodiment of the present invention.
FIG. 2 is an exploded perspective view of the rotor of FIG.
FIG. 3 is a characteristic diagram showing the relationship between the main magnetic flux amount and the salient pole ratio with respect to the width of the radial core portion between the poles.
FIG. 4 is a characteristic diagram showing the relationship between the amount of main magnetic flux and the relationship between salient pole ratios with respect to the opening angle of the gaps at both ends of the receiving hole.
FIG. 5 is a plan sectional view of a rotor showing a conventional example.
FIG. 6 is a plan sectional view of a rotor showing another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Iron core, 2, 2a, 2b ... Magnet, 3, 3a, 3b ... Accommodating hole, 4, 4a ... Space | gap part, 5, 5a, 5b ... Bridge-like core part, 8 ... Radial core part 10 ... shaft hole.

Claims (6)

  In a cross section perpendicular to the axial direction of the iron core, the iron core and a permanent magnet inserted into a receiving hole for each pole formed in the iron core, rotating in a state facing a stator having a slot, In the rotor of the permanent magnet type electric motor configured such that the interval between the housing hole and the outer periphery of the iron core is wide at the center of the housing hole and narrowed at both ends,
  A gap portion is provided at both ends of the accommodation hole, and the gap portion leaves a radial iron core portion having a circumferential width of d in the interval between the adjacent poles and the gap portion. A bridge-shaped iron core portion is left between the outer periphery of the iron core, and the gap portion has a distal end up to an opening angle θ2 narrower than an opening angle θ1 from the axis of the permanent magnet inserted into the receiving hole. And the radial width d of the radial core portion is set to be equal to or greater than the circumferential width of the slot opening of the stator slot. A rotor of a permanent magnet type electric motor characterized by   The rotor of the permanent magnet type electric motor according to claim 1, wherein a flat plate type permanent magnet is inserted into the accommodation hole.   The rotor of a permanent magnet type electric motor according to claim 2, wherein the accommodation hole is formed in a V shape with the convex side facing the axis.   2. The rotor of a permanent magnet type electric motor according to claim 1, wherein a permanent magnet having a C-shaped cross section is inserted into the accommodation hole.   The rotor of a permanent magnet type electric motor according to any one of claims 1 to 4, wherein a rare earth magnet is used as the permanent magnet.   The rotor of a permanent magnet type electric motor according to any one of claims 1 to 5, wherein the gap portion is filled with a nonmagnetic material.

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