JP4408869B2 - Induction motor vertical rotor - Google Patents

Description

  The present invention relates to a vertical rotor for an induction motor, and more particularly to a vertical rotor for an induction motor in which a molten metal such as aluminum is injected into a slit and cooled and solidified as a secondary conductor.

  A cage-type induction motor, which is a kind of induction motor, is the AC motor that is most widely used due to features such as good operating characteristics, easy handling, simple structure, and low price. A saddle type induction motor is basically composed of a stator that generates a rotating magnetic field by a winding connected to a power source, and a saddle type rotor arranged in the rotating magnetic field. The core consists of a cylindrical laminated core whose axis is supported by a rotating shaft, a secondary conductor provided in a large number of axially open type slits formed on the outer peripheral surface of the laminated core, and a laminated core. And a short-circuit ring for short-circuiting the secondary conductors at both ends.

  Here, as a method of making the secondary conductor of the saddle-shaped rotor, there is known a method of injecting a molten metal such as aluminum into the slit and cooling and solidifying it as a secondary conductor. In this case, the slit inner surface and the outer surface of the secondary conductor after cooling and solidification due to the difference between the linear expansion coefficient of the slit forming member (that is, the laminated core made of the sintered core) and the secondary conductor made of aluminum or the like. A minute gap was generated between the two, and various inconveniences were sometimes induced by this gap.

  For example, the gap between the saddle-shaped rotor and the stator may be reduced during high-speed rotation, and in the worst case, the gap becomes zero and contact between the saddle-shaped rotor and the stator, i.e., gap rubbing. May occur. This is because a centrifugal force during high-speed rotation acts on the secondary conductor in the slit, and a part of the secondary conductor jumps out of the opening of the slit due to this centrifugal force.

  FIG. 5 is an explanatory diagram of inconvenience of gap reduction and gap rubbing. In this figure, (a) and (b) show how the secondary conductor is formed. That is, (a) shows a state immediately after pouring a molten metal 3 such as aluminum into an open-type slit 2 formed in a laminated core 1 of a saddle-shaped rotor, and (b) shows that the molten metal 3 is cooled and solidified. The state when the secondary conductor 4 is formed is shown.

  In this figure, the upper end line 1a of the laminated core 1 in the figure is drawn in a horizontal straight line, but this is for convenience of illustration. Actually, it is a curve along the outer periphery curvature of the saddle rotor. The same applies to other drawings.

  In these drawings (a) and (b), when the molten metal 3 is cooled and solidified to form the secondary conductor 4, the inner circumference and the secondary of the slit 2 and the secondary due to the difference in linear expansion coefficient between the slit 2 and the secondary conductor 4. A gap 5 is created between the outer periphery of the conductor 4.

  The gap 5 is generated almost uniformly along the outer periphery of the secondary conductor 4. This is because the secondary conductor 4 is deformed in the direction in which the secondary conductor 4 is contracted with respect to the slit 2 due to the difference in the linear expansion coefficient, and the contraction is substantially the center point of the secondary conductor 4 (approximately the center of gravity of the area). This is because it proceeds toward the point P1). Therefore, the secondary conductor 4 after being cooled and solidified has a slightly smaller approximate shape with respect to the shape of the slit 2.

  (C) is a figure which shows a mode when the saddle-shaped rotor is rotating at high speed. In this figure, when the centrifugal force F accompanying high-speed rotation is applied, the secondary conductor 4 moves in the direction of the opening 2a of the slit 2, so that the neck 4a of the secondary conductor 4 becomes the outer periphery of the saddle-shaped rotor. It protrudes by a slight amount (projection amount D1) from the surface (upper end line 1a).

  Therefore, since the inner peripheral surface of the stator (not shown) is arranged via the predetermined gap length so as to face the outer peripheral surface of the saddle-shaped rotor, the gap is reduced by the protrusion of the secondary conductor 4, or In the worst case, it causes the inconvenience of causing gap rubbing.

  As a solution for such inconvenience, for example, in Patent Document 1 below, the gap 5 is filled with a resin material.

JP-A-8-237919

  However, if the minute gap between the inner surface of the slit and the outer surface of the secondary conductor is filled with a resin material, the above disadvantages during high-speed rotation (gap reduction and gap rubbing) are certainly eliminated. However, since it is necessary to perform a new process (resin material filling process) after the secondary conductor forming process, there is a problem in that the number of processes is increased and, therefore, the cost is increased.

  Therefore, the present invention provides a saddle-shaped rotor for an induction motor that can avoid the above disadvantages (gap reduction and gap rubbing) without requiring a resin material filling step by devising the shape of the slit. There is.

The present invention provides a cylindrical laminated core whose axis is supported by a rotating shaft, a secondary conductor provided in a number of axial slits formed on the outer peripheral surface of the laminated core, and the laminated core. In a saddle-shaped rotor of an induction motor provided with a short-circuit ring that short-circuits the secondary conductors at both ends, the slit includes a neck that opens on an outer peripheral surface of the saddle-shaped rotor, and the secondary on the neck And a restraining means that inhibits the movement of shrinkage of the molten metal when filled with the molten metal to be a conductor forming material.
In a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and on the outer peripheral surface of the main body portion. It has the said neck part which opens, and the overhang | projection part formed in the boundary vicinity of the both sides of the said neck part, and a main-body part, It is characterized by the above-mentioned.
According to this, when the projecting portion fills the neck portion with the molten metal that forms the secondary conductor, the restraining means that inhibits the movement of shrinkage of the molten metal is formed.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor. The neck portion opening at the outer peripheral surface, and a parallel throttle portion formed by narrowing the vicinity of the boundary between both sides of the neck portion and the main body portion substantially in parallel toward the inside of the neck portion. .
According to this, the parallel restricting portion forms a restraining means that inhibits the movement of the shrinkage of the molten metal when the neck is filled with the molten metal that forms the secondary conductor.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and the outer periphery of the main body portion It has a neck portion that opens at a surface, and a curved enlarged portion formed by enlarging the vicinity of the boundary between both sides of the neck portion and the main body portion toward the outside of the neck portion in a curved shape.
According to this, the bending expansion portion forms a restraining means that inhibits the movement of the melt contraction when the neck portion is filled with the melt as the material for forming the secondary conductor.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and the outer periphery of the main body portion It has a neck portion that opens at the surface, and a curved diaphragm portion that is formed by narrowing the vicinity of the boundary between both sides of the neck portion and the main body portion toward the inside of the neck portion in a curved shape.
According to this, when the neck is filled with the molten metal that will form the secondary conductor, the restraining means that inhibits the movement of contraction of the molten metal is formed.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and the outer periphery of the main body portion And a wedge-shaped enlarged portion formed by enlarging the vicinity of the boundary between both sides of the neck portion and the main body portion in a wedge shape toward the outside of the neck portion.
According to this, the wedge-shaped enlarged portion forms a restraining means that inhibits the movement of the molten metal contraction when the neck portion is filled with the molten metal that forms the secondary conductor.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and the outer periphery of the main body portion It has a neck portion that opens on the surface, and a wedge-shaped throttle portion that is formed by narrowing the vicinity of the boundary between both sides of the neck portion and the main body portion toward the inside of the neck portion in a wedge shape.
According to this, the wedge-shaped restricting portion forms the restraining means that inhibits the movement of the molten metal contraction when the neck portion is filled with the molten metal as the secondary conductor forming material.
Alternatively, in a preferred aspect of the present invention, the slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane perpendicular to the rotation axis of the saddle-shaped rotor, and the outer periphery of the main body portion It has a neck part opened on the surface, and a sawtooth part formed in the vicinity of the boundary between both sides of the neck part and the main body part.
According to this, the sawtooth portion forms a restraining means that inhibits the movement of shrinkage of the molten metal when the neck portion is filled with the molten metal that forms the secondary conductor.

  According to the present invention, when the neck portion is filled with the molten metal that is the material for forming the secondary conductor and cooled and solidified, the restraining means (for example, the overhang portion, the parallel throttle portion, the curved enlargement portion) provided on the neck portion of the slit. , Curved constricted portion, wedge-shaped enlarged portion, wedge-shaped constricted portion, sawtooth portion or similar shape portion) inhibits the movement of the molten metal contraction. For this reason, the shrinkage amount of the secondary conductor in the vicinity of the restraining means is reduced, and the gap between the slit and the secondary conductor is reduced. As a result, the slit and the secondary conductor are firmly engaged with each other at the gap reduction portion. As a result, the secondary conductor pops out, that is, due to the centrifugal force when the saddle-shaped rotor rotates at high speed, Jumping outward from the opening is suppressed or restricted. Therefore, various inconveniences due to the protrusion, for example, gap reduction with the stator and gap rubbing can be avoided. In addition, since a new process (filling process of resin material) as in the prior art is not required, the cost is not increased.

  Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the specific details or examples in the following description and the illustrations of numerical values, character strings, and other symbols are only for reference in order to clarify the idea of the present invention, and the present invention may be used in whole or in part. Obviously, the idea of the invention is not limited. In addition, a well-known technique, a well-known procedure, a well-known architecture, a well-known circuit configuration, and the like (hereinafter, “well-known matter”) are not described in detail, but this is also to simplify the description. Not all or part of the matter is intentionally excluded. Such well-known matters are known to those skilled in the art at the time of filing of the present invention, and are naturally included in the following description.

  FIG. 1 is a perspective view of a saddle type induction motor according to the present embodiment. In this figure, a saddle type induction motor 10 has a stator 13 attached to the inner peripheral surface of a frame 12 having a base 11 formed in the lower part, and a saddle type rotor 14 is attached to the inner surface side of the stator 13 in a predetermined manner. The rotating shaft 15 is inserted into the shaft core of the saddle-shaped rotor 14 so as to be separated by a gap length, and both ends of the rotating shaft 15 are rotatably supported by bearings 16 and 17 on the frame 12. Configured.

  The stator 13 and the saddle-shaped rotor 14 are each composed of a laminated core such as a sintered core, and the laminated core of the stator 13 (hereinafter referred to as the stator core 13a) is arranged along the circumferential direction of the stator 13. Teeth 13b arranged at intervals are formed, and a winding 13c is accommodated in each tooth 13b.

  On the other hand, in the laminated iron core of the saddle-shaped rotor 14 (hereinafter referred to as the rotor core 14a), open type slits 18 (slit 18 in this figure) are arranged at equal intervals along the circumferential direction of the saddle-shaped rotor 14. Only the opening 18x is visible, see FIG. 2 for the actual slit 18). A secondary conductor 19 made by injecting a molten metal such as aluminum into the inside of the slit 18 and cooling and solidifying it (in this figure, it is hidden behind the rotor core 14a and cannot be seen. 2), and the ends of all secondary conductors 19 are electrically connected and short-circuited by end rings 20, 21 attached to both ends of the rotor core 14a. Yes.

  FIG. 2 is a cross-sectional view of the stator 13 and the saddle rotor 14. In this figure, the stator iron core 13a and the rotor iron core 14a each have a concentric substantially donut shape, and the outer diameter of the rotor iron core 14a is slightly smaller than the inner diameter of the stator iron core 13a. . The difference between the inner diameter and the outer diameter is the gap length between the stator 13 and the saddle-shaped rotor 14. In addition, the circular opening 14c opened in the axial center of the rotor core 14a is an attachment hole of the rotating shaft 15 (refer FIG. 1).

  As already described, tooth portions 13b are formed at equal intervals along the circumferential direction of the stator core 13a, and the windings 13c are accommodated in these tooth portions 13b. In addition, equally spaced slits 18 are formed along the circumferential direction of the rotor core 14 a, and secondary conductors 19 are provided in these slits 18.

  FIG. 3 is an enlarged view of a portion A in FIG. 2, and is an enlarged view of one slit 18. In this figure, (a) and (b) show how the secondary conductor 19 is formed in the present embodiment. That is, (a) shows a state immediately after the molten metal 3 such as aluminum is injected into the slit 18 formed in the rotor core 14a, and (b) shows the secondary conductor 19 formed by cooling and solidifying the molten metal 3. It shows the situation when

  In this figure as well, the upper end line 14b of the rotor core 14a is drawn in a horizontal straight line for convenience of illustration. Actually, it is a curve along the outer periphery curvature of the rotor core 14a. The same applies to other drawings.

  In these drawings (a) and (b), when the molten metal 3 is cooled and solidified to form the secondary conductor 19, due to the difference in linear expansion coefficient between the slit 18 and the secondary conductor 19, as in the prior art at the beginning, A gap 22 is created between the inner periphery of the slit 18 and the outer periphery of the secondary conductor 19. The difference from the prior art is that the gap 22 does not occur uniformly along the outer periphery of the secondary conductor 19.

  This difference will be described. As shown in FIG. 3, the slit 18 according to the present embodiment reaches the opening of the slit 18 continuously from the main body 18 a, whose diameter is slightly increased radially from the rotation center point of the rotor core 14 a. Although it is similar to the prior art in that it has a shape composed of a neck portion 18 b, the difference in configuration is that the shape of the neck portion 18 b gradually tapers toward the opening of the slit 18. There is.

  By having such a difference, the slit 18 of the present embodiment is provided with an overhanging portion 18c facing the vicinity of the base of the neck portion 18b (near the boundary with the main body portion 18a), and the overhanging portion 18c causes the neck portion 18b. The narrowest part can be formed along the radial direction.

  When the molten metal 3 such as aluminum is poured into the slit 18 having such a characteristic shape and cooled and solidified, a secondary conductor 19 that is substantially similar to the slit 18 and slightly contracted is formed. The secondary conductor 19 also has a shape substantially similar to the slit 18, that is, a main body portion 19 a that radially expands slightly from the rotation center point of the rotor core 14 a, and an opening portion of the slit 18 that is continuous with the main body portion 19 a. And a narrow portion 19c formed on the neck portion 19b. Incidentally, the narrow portion 19c is formed by the overhanging portion 18c of the slit 18, and the overhanging portion 18c forms the “narrowest portion” along the radial direction of the neck portion 18b as described above. Therefore, it is referred to as a “narrow part” for convenience in correspondence with such a part.

  The molten metal 3 injected into the slit 18 is gradually cooled and solidified to finally form the secondary conductor 19 having the above-described configuration. Here, the molten metal 3 is contracted in the process of solidification from the molten metal, and the protruding portion 18c of the slit 18 functions as a restraining means that inhibits the movement of the contraction. That is, although the gradually cooled molten metal 3 starts to contract from the outside toward the substantially cross-sectional center P2 of the slit 18, the protruding portion 18c of the slit 18 obstructs the contraction (inhibits the movement of the contraction). The amount of contraction of the narrowed portion 19c of the secondary conductor 19 formed corresponding to the protruding portion 18c is smaller than that of other portions. A short arrow extending from top to bottom toward P2 in FIG. 3B expresses a small amount of contraction by the length of the arrow. As a result, the gap 22 formed between the projecting portion 18 c of the slit 18 and the narrow portion 19 c of the secondary conductor 19 becomes narrower than the gap 22 of other portions.

  Now, the secondary conductor 19 of the present embodiment after formed in this way is loosely mounted in the slit 18 with a slight gap 22, that is, with a slight play. As described above, there is little play (small gap 22) between the protruding portion 18c of the slit 18 and the narrow portion 19c of the secondary conductor 19 as described above. For this reason, the movement of the slit 18 in the idle state is restricted or restricted by the portion of the little play (the protruding portion 18c of the slit 18 and the narrow portion 19c of the secondary conductor 19).

  And even if it is a case where the centrifugal force F at the time of high-speed rotation acts with respect to the secondary conductor 19 by this restriction | limiting or the effect | action of regulation, as shown in FIG.3 (c), the slit 18 of the secondary conductor 19 is applied. Can be suppressed, and the protruding amount D2 of the secondary conductor 19 can be made much smaller than the protruding amount D1 (see FIG. 5) of the prior art.

  Thus, according to this embodiment, since the protrusion amount D2 of the secondary conductor 19 can be reduced, the gap reduction and gap rubbing between the stator 13 and the saddle rotor 14 can be surely avoided. In addition, since a new process (filling process of resin material) as in the prior art is not required, the cost is not increased.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various developments and modifications are included within the scope of the technical idea.

  In the above embodiment, the slit 18 has a main body 18a whose diameter is slightly increased radially from the rotation center point of the rotor core 14a, and a neck that reaches the opening of the slit 18 continuously from the main body 18a. 18b and a protruding portion 18c formed on the neck portion 18b. Needless to say, these only show one of the preferred shapes of the slit 18.

  An object of the present invention is to suppress the protrusion amount D2 of the secondary conductor 19 and avoid gap reduction and gap rubbing without requiring a new process (resin material filling process) as in the prior art. There is. And in the present invention, in order to achieve this problem, the shape of the slit 18 is devised, and the above embodiment is an example of this contrivance.

  When the principle of the above-described embodiment is verified, the suppression of the protrusion amount D2 of the secondary conductor 19 is because the gap 22 between the protruding portion 18c of the slit 18 and the narrowed portion 19c of the secondary conductor 19 is narrowed after all. It is. Accordingly, it can be said that the essence of the present invention is to provide such a structure with a restraining means on the neck portion 18b of the slit 18.

  An example of such a structure is as shown in the above embodiment. That is, by forming the neck portion 18b that continues to the main body portion 18a of the slit 18 and reaches the opening portion of the slit 18, the protruding portion 18c can be formed on the neck portion 18b. Various modifications are possible.

  FIG. 4 is a diagram showing some other modifications in place of the overhanging portion 18c. First, (a) is one in which a parallel diaphragm portion 18d is formed on the neck portion 18b of the slit 18 (first modified example). That is, the vicinity of the base of the neck portion 18b is narrowed in parallel toward the inside of the neck portion 18b, and the throttle portion is defined as a parallel throttle portion 18d. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  (B) is one in which a curved enlarged portion 18e is formed on the neck portion 18b of the slit 18 (second modified example). That is, the vicinity of the base of the neck portion 18b is enlarged in a curved shape toward the outside of the neck portion 18b, and the enlarged portion is a curved enlarged portion 18e. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  (C) is one in which a curved diaphragm 18f is formed on the neck 18b of the slit 18 (third modification). That is, the vicinity of the base of the neck portion 18b is narrowed in a curved shape toward the inside of the neck portion 18b, and the narrowed portion is used as a curved diaphragm portion 18f. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  (D) shows a wedge-shaped enlarged portion 18g formed on the neck 18b of the slit 18 (fourth modification). That is, the vicinity of the base of the neck portion 18b is enlarged in a wedge shape toward the outside of the neck portion 18b, and the enlarged portion is a wedge-shaped enlarged portion 18g. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  (E) shows a wedge-shaped throttle portion 18h formed on the neck portion 18b of the slit 18 (fifth modified example). That is, the vicinity of the base of the neck portion 18b is narrowed in a wedge shape toward the inside of the neck portion 18b, and the narrowed portion is a wedge-shaped throttle portion 18h. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  (F) shows a case where a sawtooth portion 18i is formed on the neck portion 18b of the slit 18 (sixth modification). That is, a sawtooth is formed near the base of the neck portion 18b, and the sawtooth portion is a sawtooth portion 18i. Even if it does in this way, the protrusion amount of the secondary conductor 19 can be suppressed and gap reduction and gap rubbing can be avoided reliably.

  Although various modifications have been described above, these modifications are merely embodiments that embody the essence of the present invention, and the outer edge of the technical idea of the present invention should be judged only from the description of each modification. Don't be. For example, the parallel diaphragm portion 18d of the first modified example is not necessarily “parallel”, and the curved enlarged portion 18e and the curved diaphragm portion 18f of the second modified example and the third modified example are also There is not necessarily a “curvature of the same curvature”. Similarly, the wedge-shaped enlarged portion 18g and the wedge-shaped narrowed portion 18h of the fourth and fifth modified examples are not necessarily “acute angle wedges”, and the saw-toothed portion 18i of the sixth modified example. However, it is not necessarily “sawtooth”. Any of them may have a similar shape. In short, it may have a structure that can form a restraining means for inhibiting the movement of contraction of the molten metal 3 at the neck portion 18b of the slit 18.

It is a perspective view of a saddle type induction motor concerning this embodiment. FIG. 3 is a cross-sectional view of a stator 13 and a saddle-shaped rotor 14. It is the A section enlarged view of FIG. It is a figure which shows some other examples replaced with the overhang | projection part 18c. It is inconvenient explanatory drawing of gap reduction or gap rubbing.

Explanation of symbols

10 Vertical induction motor (induction motor)
14 Vertical rotor 14a Rotor core (laminated core)
15 Rotating shaft 18 Slit 18a Body 18b Neck 18c Overhang (Restricting means)
18d Parallel diaphragm (restraint)
18e Curve expansion part (restraint means)
18f curved diaphragm (restraint means)
18g Wedge-shaped enlarged part (restraint means)
18h Wedge-shaped throttle (restraint)
18i sawtooth part (restraint means)
19 Secondary conductor 20, 21 Short-circuit ring

Claims (8)

A cylindrical laminated iron core whose shaft core is supported by a rotating shaft, a secondary conductor provided in a number of axial slits formed on the outer peripheral surface of the laminated iron core, and at both ends of the laminated iron core In the induction motor saddle rotor with a short-circuit ring that short-circuits the secondary conductors,
The slit has a neck portion that opens to the outer peripheral surface of the saddle-shaped rotor, and restraining means that inhibits movement of the melt contraction when the neck portion is filled with a melt that forms the secondary conductor. A vertical rotor for an induction motor characterized by that.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion that opens on the outer peripheral surface of the main body portion; 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising an overhang portion formed near a boundary between both sides of the neck portion and the main body portion.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion that opens on the outer peripheral surface of the main body portion; 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising a parallel throttle portion formed by narrowing the vicinity of the boundary between both sides of the neck portion and the main body portion substantially in parallel toward the inside of the neck portion.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion opens on the outer peripheral surface of the main body portion, and the neck portion 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising a curved enlarged portion formed by enlarging the vicinity of the boundary between both sides of the main body and the main body in a curved shape toward the outside of the neck.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion opens on the outer peripheral surface of the main body portion, and the neck portion The induction motor saddle-shaped rotor according to claim 1, further comprising a curved constriction portion formed by constricting the vicinity of the boundary between both sides of the main body portion and the main body portion toward the inside of the neck portion.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion opens on the outer peripheral surface of the main body portion, and the neck portion 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising a wedge-shaped enlarged portion formed by enlarging the vicinity of the boundary between both sides of the main body and the main body portion toward the outside of the neck portion in a wedge shape.   The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion opens on the outer peripheral surface of the main body portion, and the neck portion 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising a wedge-shaped throttle portion formed by narrowing the vicinity of the boundary between both sides of the main body portion and the main body portion in a wedge shape toward the inside of the neck portion. The slits are arranged at equal intervals around the main body portion of the saddle-shaped rotor in a plane orthogonal to the rotation axis of the saddle-shaped rotor, and the neck portion opens on the outer peripheral surface of the main body portion, and the neck portion 2. A saddle-shaped rotor for an induction motor according to claim 1, further comprising sawtooth portions formed in the vicinity of a boundary between both sides of the main body and the main body.

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