JPH1094201A - Rotor for electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a bridge portion of a rotor from deforming due to centrifugal force thereby avoiding its swelling beyond a predetermined outer diameter by making the width of an iron core portion between the end portion of the magnet and the outer peripheral portion of the iron core gradually larger than the width corresponding to the magnet at the counter-shaft side compared to the width corresponding to a magnet at the shaft side. SOLUTION: Width T1 , T2 of a bridge portion 6a, 7a between the outer peripheral portion of an iron core 1a and an end portion of an almost C-shaped section of a magnet 2a, 3a of a rotor is formed in such a manner that the width T2 corresponding to a magnet 3a at the shaft side is made larger than the width T1 corresponding to a magnet 2a at the counter-shaft side. When a rotor turns, a stress due to a centrifugal force applied to a portion at the counter-shaft side acts including a magnet 2a at the counter-shaft side for a bridge portion 6a and also including a magnet 3a at shaft side for the bridge portion 7a, but T2 is formed larger than T1 so that the bridge portion 7a is deformed by the centrifugal force and thus the portion at the counter-shaft portion of the magnet 3a does not swell beyond the predetermined outer diameter of the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adduction type rotor having a permanent magnet mounted thereon, such as a motor for driving a compressor of a refrigerator or an air conditioner, and more particularly, to a rotor in which a magnet is embedded inside an iron core. And a rotor of a so-called interior permanent magnet motor (IPM).

[0002]

2. Description of the Related Art As a rotor of the above-mentioned electric motor, one having a configuration shown in FIG. 4 is known, which is disclosed, for example, in RM-96-22 of the Institute of Electrical Engineers of Japan. The rotor shown in FIG. 4 shows a cross section perpendicular to the rotation axis 4.
Is fitted into a shaft hole provided at the center of the cylindrical laminated core 1b. The iron core 1b is provided with a plurality of receiving holes substantially similar in shape to the magnet in parallel with the shaft 4, and the receiving holes
b and 3b are respectively inserted by press fitting or the like.

The magnets 2b and 3b are substantially C-shaped in a cross section perpendicular to the axis 4 shown in the figure, and are embedded in the iron core 1b with the convex side facing the axis 4. Each pole forming the field is formed by a double magnet of the anti-axis side magnet 2b and the axis side magnet 3b.
The poles are formed, and are magnetized with the center of each magnet being the center of the magnetic pole.

The above-mentioned rotors are arranged in a stator having three-phase windings so as to face each other with a predetermined gap therebetween to constitute a permanent magnet type synchronous motor. Rotation is performed by excitation. The IPM configured as described above is characterized by the reverse saliency, and is controlled and driven to use both the reluctance torque generated thereby and the main magnetic flux torque generated by the magnet.

[0005]

SUMMARY OF THE INVENTION As shown in FIG.
In the PM rotor, as shown in FIG.
The widths T1 and T2 of the iron core portions (hereinafter referred to as bridge portions) 6b and 7b interposed between the convex and concave ends of the substantially C-shaped cross sections of the magnets 2b and 3b and the outer peripheral portion of the iron core 1b are formed extremely thin. Have been. This is because the bridge portion 6b is magnetically saturated to increase the ratio of the d-axis inductance and the q-axis inductance of the IPM, that is, the salient pole ratio, to effectively utilize the reluctance torque. However, the relationship between the width T1 of the bridge portion 6b corresponding to the non-axis-side magnet 2b and the width T2 of the bridge portion 7b corresponding to the axis-side magnet 3b has not been considered at all in the past, and in general, FIG. T1 and T2 are formed to have substantially the same dimensions as indicated by a broken line extending from FIG.

When such a rotor rotates, a stress acts on the bridge portion 6b due to the centrifugal force applied to the anti-axis side portion including the anti-axis side magnet 2b including the anti-axis side magnet 2b. In addition, a stress acts on the shaft-side magnet 3b, including the shaft-side magnet 3b, due to the centrifugal force applied to the non-shaft side portion. Therefore, since the bridge portion 7b corresponding to the shaft-side magnet 3b receives much greater stress than the bridge portion 6b corresponding to the anti-axis-side magnet 2b, the bridge portion 7b is deformed by centrifugal force, and the shaft side of the rotor is rotated. The portion on the opposite side to the magnet 3b swells beyond a predetermined outer diameter of the rotor, causing vibration,
There is a danger that noise will occur or the rotor will not rotate due to contact with the stator.

If the widths T1 and T2 of the bridge portions 6b and 7b are both widened to avoid this, the width T1 of the bridge portion 6b becomes unnecessarily large, and the magnetic saturation of this portion is insufficient. Thus, the salient pole ratio of the IPM becomes small, the reluctance torque is reduced, and the motor efficiency is deteriorated.

[0008]

According to the present invention, a magnet having a convex surface on one side, such as a substantially C-shaped or V-shaped cross section perpendicular to the axis, is provided with the convex side facing the axis for each pole. In the rotor of the electric motor configured to be embedded multiple from the anti-axis side of the iron core to the shaft side, the magnets are arranged so that both ends of the convex surface and the concave surface are close to the outer peripheral portion of the iron core. The width of the core portion interposed between the end portion of the magnet and the outer peripheral portion of the iron core is configured such that the width corresponding to the magnet arranged on the axial side is sequentially increased from the width corresponding to the magnet arranged on the opposite axis side. Is what you do.

In the section perpendicular to the axis, the width of the core portion interposed between each end portion of the non-axial side magnet and the axial side magnet adjacent in the radial direction and the outer peripheral portion of the core is set to T1. , T2, angles formed by lines connecting the iron core portion and the axis with the magnetic pole center line are α1 and α2, respectively, and from the total mass and the axis of the anti-axis side portion including the anti-axis side magnet, When the distance to the center of gravity is M1 and R1, respectively, and the total mass of the non-axis side portion including the shaft-side magnet and the distance from the axis to the center of gravity are M2 and R2, respectively, T2 is T1. × (M2R2 sinα2) / (M1
R1 sin α1) or more.

[0010]

In the schematic diagram of the rotor shown in FIG. 3, 1 is an iron core, 2 is an anti-axis side magnet, 3 is an axis side magnet, O is an axis center, and 8 is a magnetic pole center line of the magnets 2 and 3, respectively. I have. FIG.
The hatched portion in (a) indicates a portion on the opposite axis side from the arc on the axis side of the opposite axis magnet 2, the mass of this portion is M1, and the radius to the center of gravity P1 is R1. The width is T1
The maximum angle formed by the line connecting the bridge portion 6 and the axis O corresponding to the non-axis side magnet 2 with the magnetic pole center line 8 is α1.
That is, when considering the stress due to the centrifugal force acting on the bridge, the point where the width of the bridge is the narrowest and the point farthest from the magnetic pole center line 8 is conditionally severe. An angle α1 is defined by a line connecting. This is the same for the angle α2 described later.

Under the above conditions, the centrifugal force F1 acting on the center of gravity P1 is given by:

(Equation 1) It is represented by The force Ft1 applied to the cross section of the portion having the width T1 of the bridge portion 6 by the centrifugal force F1 is:

(Equation 2) Assuming that the axial length of the rotor is L, the stress σ1 is

(Equation 3) It is represented by

The hatched portion in FIG. 3 (b) indicates a portion of the shaft-side magnet 3 opposite to the arc on the shaft center side. The mass of this portion is M2, and the radius up to the center of gravity P2 is R2. Also, a bridge portion 7 corresponding to the shaft-side magnet 3 having a width dimension of T2.
The maximum angle formed by a line connecting the magnetic pole center line 8 with the line connecting the axis P and the axis O is α2. In this state, the centrifugal force F2 acting on the center of gravity P2 is

(Equation 4) Becomes Here, F2 is calculated from the hatched portion in FIG.
(A) is obtained by adding the centrifugal force F1 of Formula 1 to the centrifugal force acting on the portion excluding the hatched portion, so that the relationship of F2> F1 holds. The force Ft2 applied to the cross section of the portion having the width T2 of the bridge portion 7 by the centrifugal force F2 is:

(Equation 5) And therefore the stress σ2 is

(Equation 6) It is represented by That is, if the bridge portion 6 and the iron core portion interposed between the magnet 2 and the magnet 3 are sufficiently strong, a stress of σ2 is applied to the bridge portion 7.

Therefore, it is necessary to set the width T1 of the bridge portion 6 so that the value of σ1 in Equation 3 stays within the yield stress. Therefore,

(Equation 7) Is established. Similarly, the width T2 of the bridge portion 7 is
It is necessary to set so that the value of σ2 in Equation 6 stays within the yield stress, and the relationship of F2> F1 and α2>
Since Ft2> Ft1 is inevitable due to the relationship of α1, the width is wider than the width T1 of the bridge portion 6. That is,

(Equation 8) What is necessary is just to set.

[0014]

FIG. 1 shows an embodiment of the present invention, and shows a cross section perpendicular to a rotating shaft 4. The shaft 4 is fitted into a shaft hole provided at the center of the cylindrical iron core 1a, and supports the rotor so that the rotor faces the stator with a predetermined gap. The iron core 1a is provided with a plurality of receiving holes parallel to the shaft 4 and substantially similar in shape to the magnet. In the receiving holes, the non-axial-side magnet 2a and the axial-side magnet 3a are inserted by, for example, press fitting. It is configured.

The iron core 1a is formed by laminating a large number of thin iron plates punched into a predetermined shape in the axial direction, and the uneven portions formed by the projections provided on each thin iron plate are fitted to each other in the axially adjacent thin iron plates. It is fixed by well-known caulking clamp means or the like for fixing. The magnets 2a and 3a are made of ferrite magnets or rare earth magnets, have a substantially C shape in a cross section perpendicular to the axis 4 shown, and are embedded in the iron core 1a with the convex side facing the axis 4. Each pole forming a field is formed by a double magnet of the anti-axis side magnet 2a and the axis side magnet 3a, and one pole is formed. The magnet is magnetized with the center of each magnet as the center of the magnetic pole. In this case, a four-pole field is formed. Reference numeral 5 denotes a caulking pin which penetrates through the iron core 1a in the axial direction. End plates and the like are fixed to both ends in the axial direction, and the magnets 2a and 3a are covered.

In the rotor shown in FIG. 1, as shown in an enlarged view in FIG. 2, bridge portions 6a, 7a between the ends of the substantially C-shaped cross sections of the magnets 2a, 3a and the outer peripheral portion of the iron core 1a. The widths T1 and T2 of the widths T1 and T2 correspond to the width of the opposite axis magnet 2a, as is apparent from the broken line extending from the end of the magnet 3a.
The width T2 corresponding to the shaft-side magnet 3a is formed to be larger than that. That is, T1 is formed so as to be as thin as possible so that the magnetic flux of the magnet causes the bridge portion 6a to be magnetically saturated, and to have sufficient strength according to Equation 7 so as to sufficiently withstand the stress caused by centrifugal force. On the other hand, T2 needs to be configured so that the bridge portion 7a can sufficiently withstand the stress caused by the centrifugal force. When compared with T1, according to Equation 8, T1 × (M2R2 sin α2) / (M1R1 sin
α1) or more.

When the rotor as shown in FIG. 1 rotates, the bridge portion 6a receives a stress due to the centrifugal force applied to the non-axial side portion including the non-axial side magnet 2a.
On the other hand, a stress due to the centrifugal force applied to the anti-axial side portion, including the axial side magnet 3a, acts on the bridge portion 7a, but because T2 is formed larger than T1 as described above. The bridge portion 7a is not deformed by the centrifugal force, and the portion on the opposite side of the magnet 3a from the magnet 3a does not expand beyond the predetermined outer diameter of the rotor.

Further, since T1 is not increased unnecessarily, the bridge portion 6a can be sufficiently magnetically saturated to increase the salient pole ratio, and the reluctance torque can be effectively used to improve the motor efficiency. It is. The width T2 of the bridge portion 7a of the shaft-side magnet 3a is widened by adopting the present invention. However, the shaft-side magnet 3a has a larger area and physique than the anti-axis-side magnet 2a, so that the amount of magnetic flux is large. Since magnetic saturation easily occurs, there is no problem in characteristics. Also, the wider bridge portion has the effect that the stator flux contributing to the reluctance torque flows in and out smoothly, and from this aspect also the characteristics of the electric motor can be improved.

In the above embodiment, each pole of the rotor field is constituted by the double magnets 2a and 3a. However, it is needless to say that a triple magnet or the like may be used. . In this case, the widths of the bridge portions of the non-axial side magnet and the axial side magnet adjacent in the radial direction may be T1 and T2, respectively, and these may be configured in the above-described dimensional relationship. Further, the configuration of the present invention can be similarly applied to a case where a magnet shape having a substantially V-shaped cross section perpendicular to the shaft 4 is adopted as a magnet shape different from the rotor shown in the embodiment.

[0020]

According to the present invention, the bridge portion of the rotor is prevented from being deformed by the centrifugal force and swelling beyond a predetermined outer diameter, and a motor having less vibration and noise can be constructed.
At the same time, there is no possibility that the rotor comes into contact with the stator and cannot be rotated, so that an electric motor with excellent quality can be obtained. Further, since the bridge portion is hardly deformed, there is no need to use an expensive iron core material having high hardness for the purpose of increasing the yield stress, and there is a feature that a low-cost rotor can be configured. Further, since the salient pole ratio can be increased and the inflow and outflow of the stator magnetic flux can be made smooth, the reluctance torque can be effectively utilized, and the characteristics of the electric motor can be improved.

[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 enlarged view of a main part of FIG.

FIG. 3 is a schematic plan view of a rotor illustrating a centrifugal force and a stress applied to a bridge portion.

FIG. 4 is a plan sectional view of a rotor showing a conventional example.

FIG. 5 is an enlarged view of a main part of FIG. 4;

[Explanation of symbols]

 1, 1a, 1b Iron core 2, 2a, 2b, 3, 3a, 3b Magnet 4 axis 5 Caulking pin 6, 6a, 6b, 7, 7a, 7b Bridge section

Claims (2)

[Claims] 1. A magnet having a substantially C-shaped or substantially V-shaped cross section perpendicular to the axis and having a convex surface on one side and a concave surface on the other side. In the rotor of the electric motor configured to be embedded multiple over the side, the magnets are arranged so that both ends of the convex surface and the concave surface are close to the outer peripheral portion of the iron core, and the ends of the magnet and the core A rotor for an electric motor, wherein a width of an iron core interposed between an outer peripheral portion and a width corresponding to a magnet arranged on an axial side is sequentially increased from a width corresponding to a magnet arranged on an opposite axis side. 2. In a cross section perpendicular to the axis, a width dimension of a core portion interposed between each end portion of the non-axial side magnet and the axial side magnet radially adjacent to each other and the outer peripheral portion of the core is set to T1. , T2, angles formed by lines connecting the iron core portion and the axis with the magnetic pole center line are α1 and α2, respectively, and from the total mass and the axis of the anti-axis side portion including the anti-axis side magnet, When the distance to the center of gravity is M1 and R1, respectively, and the total mass of the non-axis side portion including the shaft-side magnet and the distance from the axis to the center of gravity are M2 and R2, respectively, T2 is T1. × (M2R2sinα2) / (M1R1s
2. The rotor for an electric motor according to claim 1, wherein inα1) or more.