JPH1169668A - Stator core of outer rotor type motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the extentions of slot openings as possible and adjust the widths of the slot openings properly even if a stator core is formed by a winding process. SOLUTION: A stripe steel plate 23 is composed of a stripe part 24 for forming a yoke and protruding segments 25 for forming teeth. Extending parts 26a and 26b on the tip parts of the protruding segments 25 adjacent to each other are formed so as to have the tip parts of the extending parts 26a and 26b overlap each other in the widethwise direction of the stripe steel plate 23. If the stripe steel plate 23 is warped into an annular form by plastic deformation with the protruding segments on the outer circumference side, the adjacent protruding segments 25 are largely separated from each other on the outer circumference side but, because of the overlaps of the adjacent extending parts 26a and 26b in the widthwise direction, the extention of a distance between the extending parts 26a and 26b can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stator core of an external rotation type motor formed by winding a steel strip.

[0002]

Conventionally, a stator core of a motor has been used in which stamped steel sheets are laminated. However, in the case of a stator core having a large diameter, there is a disadvantage in that the inner portion is punched out and a large portion is wasted. As a configuration for eliminating such material waste, a method is employed in which a belt-shaped steel plate is plastically deformed in an annular shape, and a stator core is formed by winding the annular portion while laminating it. Such a method of processing a strip-shaped steel sheet is also referred to as winding processing. Hereinafter, an example of the case where the stator core is formed by the strip-shaped steel plate will be described with reference to FIG.

FIG. 15 (a) shows a part of a strip-shaped steel sheet 1. In this strip-shaped steel sheet 1, a projecting piece 3 for forming teeth protrudes from a strip-shaped section 2 for forming a yoke of a stator core. It is configured. The projecting portion 4 provided at the tip of the projecting piece 3 is formed so as to extend to the vicinity of the projecting portion 4 of the adjacent projecting piece 3. Then, the belt-shaped steel plate 1 having the above-described configuration is plastically deformed into an annular shape as shown in FIG. 15B, and the annular portion is wound while being laminated, thereby forming a stator core (not shown).

However, in the stator core of the external rotation type motor, the strip-shaped steel plate 1 is deformed in a ring shape so that each protruding portion 3 is located on the outer peripheral side. At this time, in the projecting piece 3, the distance between the adjacent projecting piece 3 increases toward the outer peripheral side, so that the distance between the projecting parts 4 located on the outermost peripheral side of the projecting piece 3 greatly increases. Become. Therefore, in the stator core formed by the above method, the distance between the teeth heads formed by the overhangs 4, that is, the width of the opening of the slot is large.

Although the opening of the slot is originally provided for the winding operation of the winding, the width dimension thereof is a size which does not impair the workability of the winding operation of the winding, for example, the winding diameter. It is necessary to suppress it to several times. This is because, if the width of the opening of the slot is large, the reluctance is correspondingly increased and the output of the motor is reduced, and the cogging torque is increased and the vibration noise and the rotation unevenness of the motor are increased. It is.

However, as described above, when the stator core is formed by deforming the strip-shaped steel sheet 1 into an annular shape, the distance between the overhanging portions 4 of the strip-shaped steel sheet 1 is increased, so that the width dimension of the slot opening is increased. . Moreover, since the size of the width of the slot opening is determined by the diameter of the stator core, the number of teeth, and the length of the teeth, it cannot be set according to the winding diameter or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to minimize the spread of a slot opening even when it is formed by winding a strip-shaped steel plate, and to reduce the width of the slot opening. It is an object of the present invention to provide a stator core of an external rotation type motor that can appropriately adjust the rotation angle.

[0008]

According to a first aspect of the present invention, there is provided a stator core for an external rotation type motor, wherein a projecting portion for forming teeth having a substantially T-shape having a protruding portion at a tip portion has substantially equal intervals. The plastic strip is formed by laminating the belt-shaped steel plate formed into a ring so that the protruding portion is located on the outer peripheral side, and the annular portion is laminated. The present invention is characterized in that the overhang portion is configured to overlap in the width direction of the strip-shaped steel plate.

[0009] According to such a configuration, in the state of the strip-shaped steel sheet, the overhang portions of the adjacent protruding pieces overlap in the width direction. The spread of the distance between adjacent overhangs can be suppressed by the amount of. In addition, by changing the overlapping dimension of the projecting portion, it is possible to change the spreading dimension of the projecting portion after the belt-shaped steel plate is deformed into a ring shape, so that the width dimension of the opening of the slot can be appropriately adjusted.

In this case, the overhanging portion is provided with a long overhanging portion and a short overhanging portion, and the projecting portion having the long overhanging portion and the projecting portion having the short overhanging portion are alternately provided. (Claim 2) The configuration in which the outer peripheral surface of the long overhanging portion is located inside the outer peripheral surface of the short overhanging portion (Claim 3) further improves cogging torque. This is a good configuration. Further, when the projecting portion of the protruding portion of the strip-shaped steel plate is configured to have a shape such that a gap is formed between the projecting portions of the adjacent protruding portions when the strip-shaped steel plate is plastically deformed in an annular shape. Good (claim 4).

On the other hand, in the stator core of the external rotation type motor according to the fifth aspect of the present invention, substantially T-shaped teeth forming projecting pieces having a projecting portion at the tip are formed at substantially equal intervals. The belt-shaped steel plate is plastically deformed in an annular shape such that the protruding piece portion is on the outer peripheral side, and is configured by laminating this annular portion, wherein the overhanging portion has a long overhanging portion and a short overhanging portion. Along with providing the protruding portion having the long overhanging portion and the protruding portion having the short overhanging portion alternately, when laminating the strip-shaped steel sheet, the long overhanging portion and the short overhanging portion are laminated. It is characterized by having comprised so that.

Further, in the stator core of the external rotation type motor according to the sixth aspect of the present invention, the teeth forming protrusions having a substantially T-shape having a projecting portion at the tip end are formed at substantially equal intervals. The belt-shaped steel plate is plastically deformed in an annular shape such that the protruding portion is on the outer peripheral side, and is formed by stacking the annular portion, and one of the protruding portions of each protruding portion of the belt-shaped steel plate. , And the other is shortened, so that when an annular portion plastically deformed in an annular shape is stacked, a long overhang portion and a short overhang portion are stacked.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, FIG. 3 shows an entire configuration of a permanent magnet type motor which is an external rotation type motor according to the present embodiment. In FIG. 3, a stator 12 is mounted on a sleeve 11 provided at a stationary part (not shown). The stator 12 includes a stator core 13 and windings 14 wound around the stator core 13. On the other hand, a rotating shaft 17 of a rotor 16 is supported on the sleeve 11 via a bearing 15. And
The rotor 16 has a permanent magnet 18 facing the outer peripheral surface of the stator core 13.

FIG. 2 shows a state where the windings 14 are removed from the stator 12, that is, a part of the stator core 13 is
FIG. The stator core 13 has an even number, for example, 24 teeth 20 radially protrudingly provided on an outer peripheral portion of an annular yoke 19. Also,
The tip of each tooth 20 is formed wider than the other portions of the teeth 20, so that the teeth head 21
Is configured. As a result, the adjacent teeth 20
A slot 2 in which a space between the windings 14 is accommodated
The width of the opening 2 is smaller than the width of the other portion of the slot 22.

Here, at the tip of the teeth 20,
Two types of teeth heads 21a and 21b having the same circumferential width and different shapes are arranged alternately. One of the teeth heads 21a has a curved outer peripheral surface 21c corresponding to the inner peripheral surface of the rotor 16.
And an inner peripheral surface 21d inclined outward from the teeth 20 toward both sides in the circumferential direction.
Are formed narrow. On the other hand, a step 21g is provided on the outer peripheral surface of both ends 21f in the circumferential direction of the other tooth head 21b, so that both ends 21f in the circumferential direction are formed narrow.

The stator core 13 is formed by plastically deforming the belt-shaped steel plate 23 shown in FIG. 1 into an annular shape and winding the annular portion while stacking it in the axial direction. The band-shaped steel plate 23 is formed by, for example, pressing a silicon steel plate, and a band-shaped portion 24 for forming the yoke 19 and a number of teeth 20 protruding from one end of the band-shaped portion 24 in the width direction at substantially equal intervals. And a projecting piece 25 for formation.

Around half of the protruding pieces 25 are attached to both ends in the longitudinal direction (left and right directions in FIG. 1) of the strip-shaped steel plate 23 in correspondence with the teeth head 21a of the stator core 13. A protruding portion 26a is provided. Also,
A tooth head 21b is attached to the tip of the remaining protruding piece 25.
Corresponding to the above, there is provided an overhang portion 26b that overhangs both sides in the length direction of the strip-shaped steel plate 23. The projecting pieces 25 having the projecting portions 26a and the projecting pieces 25 having the projecting portions 26b are arranged alternately.

The overhang portion 26a has a slightly curved outer peripheral surface 26c and an inner peripheral surface 26d inclined toward both sides from the projecting piece 25 side, similarly to the teeth head 21a. Both ends 26e are formed narrow.
On the other hand, in the overhang portion 26b, similarly to the tooth head 21b, a step portion 26g is provided on the outer peripheral surface of both end portions 26f, and both end portions 26f are formed to be narrow.

Then, both ends 26e of the overhang portion 26a are formed.
Are configured to be located in the step portions 26g of the adjacent overhang portions 26b. Thereby, both end portions 26e of the overhang portion 26a are configured to overlap both end portions 26f of the overhang portion 26b in the width direction of the strip-shaped steel plate 23.

The stator steel core 13 is formed by plastically deforming the strip-shaped steel plate 23 having the above-described configuration into an annular shape so that the protruding portion 25 is located on the outer peripheral side, and winding and laminating the annular portion. . At this time, since the end 26e of the protruding portion 26a of the adjacent protruding piece 25 and the end 26f of the protruding portion 26b overlap in the width direction, even if the tip of the adjacent protruding piece 25 is separated, Separation between the overhang portions 26a and 26b by the overlap is suppressed. Therefore, the width of the opening of the slot 22 of the stator core 13 is reduced. In this embodiment, the slot 2
The overlapping dimension of the overhangs 26a and 26b is set so that the width of the opening 2 is about five times the outer diameter of the winding 14, for example, without impairing the workability of the winding of the winding 14. Have been.

Although not shown, a notch is intermittently formed in a portion of the strip 24 of the strip steel plate 23 corresponding to the inner peripheral surface side of the yoke 19. This suppresses the occurrence of wrinkles when the strip-shaped steel plate 23 is plastically deformed in a ring shape.

According to this embodiment having such a configuration, in the strip-shaped steel plate 23, the projecting portions 26a, 2
6b are formed so that both end portions thereof overlap in the width direction of the strip-shaped steel plate 23. Therefore, even when the stator core 13 is formed by plastically deforming the strip-shaped steel plate 23 in a ring shape, the width of the opening of the slot 22 is not limited. Dimensions can be reduced.

Here, if there is no opening in the slot of the stator core, the magnetic energy of each gap changes, but no cogging torque is generated because the magnetic energy does not change if the total amount is taken. That is, the cogging torque is generated when the magnetic energy fluctuates due to the opening of the slot. Accordingly, by suppressing the width of the opening of the slot 22 to be small as in the present embodiment, the cogging torque can be reduced as compared with the conventional one, and as a result, the rotational accuracy of the motor can be improved. . Further, since the magnetic resistance of the stator 12 is reduced, the effect of increasing the magnetic flux density and increasing the motor output is also obtained.

In addition, according to the present embodiment, the steel strip 23
The width of the opening of the slot 22 is adjusted to a desired size, for example, 5 mm of the diameter of the winding 14 without impairing the workability of the winding operation, by adjusting the overlapping dimension of the overhanging portion 26a and the overhanging portion 26b. It can be set to about twice.

FIGS. 4 and 5 show a second embodiment of the present invention, and the points different from the first embodiment will be described. The same parts are denoted by the same reference numerals. FIG.
FIG. 9 is a diagram illustrating a part of the stator core 13 according to the second embodiment. In the present embodiment, the stator core 13 includes a tooth 20 having a wide teeth head 31 having a large circumferential width. The teeth 20 having the narrow teeth heads 32 having a small circumferential width are alternately provided.

The wide teeth head 31 has an outer peripheral surface 31a and an inner peripheral surface 31b which form a curved surface corresponding to the inner peripheral surface of the rotor 16, and both end portions 31c are formed to be slightly narrower. ing. In addition, the narrow teeth head 32
Has an outer peripheral surface 32a having a curved shape corresponding to the inner peripheral surface of the rotor 16 and an inner peripheral surface 32b inclined from the inner peripheral side toward the outer peripheral side, and both end portions 32c are formed narrow. Have been. And the outer peripheral surface 31 of the wide teeth head 31
a is configured to be located inside the outer peripheral surface 32a of the narrow teeth head 32. Therefore, the outer peripheral surface 32a of the narrow teeth head 32 is larger than the outer peripheral surface 31a of the wide teeth head 31 in the permanent magnet 1 of the rotor 16.
It is configured to approach the 8 side.

As shown in FIG. 4, the strip-shaped steel plate 23 has a projecting piece 25 having a wide projecting portion 33 corresponding to the wide teeth head 31 and a projecting portion 34 corresponding to the narrow teeth head 32. Are alternately provided. Therefore, the overhang portion 33 has an outer peripheral surface 33a and an inner peripheral surface 33b that are slightly curved.
Both ends 33c are slightly narrower. The overhang portion 34 has an outer peripheral surface 34a having a curved surface and an inner peripheral surface 34b having an inclined surface, and both end portions 34c are formed narrow. At this time, both ends 33c of the wide projecting portion 33
Is located closer to the band portion 24 than the inner peripheral surface 34b of both end portions 34c of the adjacent narrow projecting portion 34 so that the projecting portion 33 and the projecting portion 34 overlap in the width direction of the band-shaped steel plate 23. Is configured.

According to this embodiment, the teeth 20 of the stator core 13 are provided with the wide teeth heads 31 and the narrow teeth heads 32 alternately, so that the cogging torque of each slot 22 is reduced. The slot 22 is configured to be offset by the cogging torque of the slot 22. Therefore, the cogging torque of the entire motor can be reduced.

Moreover, the outer peripheral surface 31a of the narrow teeth head 32 is replaced with the outer peripheral surface 32a of the narrow teeth head 32.
The narrow teeth head 32 is arranged closer to the permanent magnet 18 side than the wide teeth head 31. Therefore, the difference in magnetic resistance due to the difference in circumferential length between the wide tooth head 31 and the narrow tooth head 32 is reduced by the two tooth heads 3.
This can be offset by the difference in the gap size between the permanent magnets 18 and 1, 32, and the cogging torque can be further reduced.

FIG. 6 shows a third embodiment of the present invention, and the points different from the second embodiment will be described. The same parts are denoted by the same reference numerals. In the present embodiment, the outer peripheral surface 33 of the wide overhang portion 33 of the strip-shaped steel plate 23 is used.
a was formed in a circular arc shape. In this case, the center of the arc surface is
It is set so as to be located on the outer peripheral side of the winding center of the stator core 13 (a portion corresponding to the rotation center of the rotor 16). At this time, both ends 33c of the overhang portion 33
Are configured so as to be located along the inner peripheral surface 34b of both ends 34c of the overhang portion 34.

Accordingly, when the projecting portions 33 and 34 are plastically deformed in an annular shape of the strip-shaped steel plate 23, the adjacent projecting portions 2
5, the both ends 33c of the overhanging portion 33 and the overhanging portion 34
Does not interfere with each other. Therefore, unnecessary deformation during processing can be prevented as much as possible.

In this embodiment, the overhang portion 33 is provided.
The outer peripheral surfaces 33a of the both ends 33c of the overhanging portion 33 are
4 along the inner peripheral surface 34b,
The projecting portions 33 and 34 are configured so as not to interfere with each other. However, a gap is provided between both end portions 33c of the overhang portion 33 and both end portions 34c of the overhang portion 34 so that the two overhang portions 33 and 34 do not interfere with each other during processing. The inner peripheral surface 34b may be configured such that both end portions 33c of the overhang portion 33 do not abut during the winding process.

FIGS. 7 to 10 show a fourth embodiment of the present invention. First, FIG.
In this embodiment, the stator iron core 13 is also provided with 24 teeth 2 around the yoke 19 in this embodiment.
0 is protrudingly provided. And each tooth 2
The tooth heads 35 at the leading end of 0 have the same length in the circumferential direction. In this embodiment,
The stator core 13 is formed by forming a ring 37 by plastically deforming a belt-shaped steel plate 36 into a ring, and laminating the ring 37. Hereinafter, this configuration will be described with reference to FIG.
This will be described with reference to FIG.

First, in FIG. 9, the belt-shaped steel plate 36 is composed of a belt-like portion 38 and twenty-four projecting portions 39 provided at one end in the width direction of the belt-like portion 38 at equal intervals.
These protruding pieces 39 are all formed to have the same length and the same width. The protruding pieces 39 are alternately provided with long overhangs 39a, 39a at both ends and short overhangs 39b, 39b at both ends. It is arranged in. At this time, the end 39c of the long overhang 39a is connected to the end 39c of the adjacent short overhang 39b.
It is configured to extend to near d.

An annular body 37 shown in FIG. 10 is formed by plastically deforming the belt-shaped steel plate 36 having such a configuration so that the both ends 36a, 36a are in contact with each other. Therefore, the annular body 37 has a long overhang 39a,
A protruding piece 39 having a short 39a and short overhangs 39b, 3
The protrusions 39 having 9b are alternately arranged.

The stator core 13 is formed by laminating the annular members 37. At this time, as shown in FIG. 8, the teeth head 35 is configured such that long overhangs 39a and short overhangs 39b are alternately arranged in the laminating direction. As a result,
The circumferential length of each tooth head 35 is apparently
The width is the same as the width of the protruding portion 39 having the long overhang portions 39a on both sides in the circumferential direction, which is different from the conventional case where the stator core is formed by a strip-shaped steel plate having the protruding portion having the same width of the overhang portion as in the related art. Also, the width of the opening of the slot 40 is reduced.

In this case, the slot 40 is larger than the conventional one.
Although the width of the opening is smaller, the gap area between the adjacent tooth heads 35 is substantially the same as that of the conventional one. Because each teeth head 35
This is because a gap G is formed between the long overhangs 39a, 39a located on both sides of the short overhang 39b at both ends. Therefore, the magnetic resistance between the rotor 16 and the stator 12 in the motor of the present embodiment is also equal.

However, in this embodiment, the magnetic flux from the permanent magnet 18 facing the gap G at both ends of the teeth head 35 is curved toward the long overhang portion 39a adjacent to the gap G, and is rotated in the rotational direction (circumferential direction). Does not bend. for that reason,
Even if the magnetic flux resistance is the same, the magnetic flux component curved in the rotating direction can be reduced, and as a result, the cogging torque can be reduced. Also in the present embodiment, the width of the opening of the slot 40 can be adjusted by adjusting the length of the long overhang portion 39a.

FIGS. 11 to 14 show a fifth embodiment of the present invention, and the differences from the fourth embodiment will be described. The same parts are denoted by the same reference numerals. In the fifth embodiment, instead of the strip-shaped steel sheet 36, the strip-shaped steel sheet 41 is plastically deformed in an annular shape to form an annular body 42, and the stator body 13 is formed by stacking the annular bodies 42. I have.

As shown in FIG. 13, the strip-shaped steel plate 41 is composed of 24 projecting portions 44 projecting from the band-shaped portion 43. The tip of the projecting portion 44 has one side (shown in FIG. 13). A long overhang 45a is provided on the right side) and a short overhang 45b is provided on the other side. And also in this case, the end 45c of the long overhang 45a is
It is configured to extend to the vicinity of the end 45d of b. By annularly plastically deforming such a band-shaped steel plate 41, an annular body 42 as shown in FIG. 14 is formed.

The annular body 42 shown in FIG. 14 and the annular body 42 in a state where the annular body 42 is turned upside down, that is, the annular body 42 shown in FIG. The stator core 13 is formed by alternately stacking the opposite annular bodies 42. As a result, as shown in FIG. 12, long projecting portions 45a are provided on both sides of the stator core 13 in the circumferential direction of each tooth head 35.
And the short overhangs 45b are alternately arranged, and a gap G is generated between the long overhangs 45a, 45a located on both sides of the short overhang 45b.

Accordingly, also in this embodiment, the length in the circumferential direction of each tooth head 35 is apparently the same as the length when the long overhang portions 45a are provided on both sides in the circumferential direction. For this reason, the width of the opening of the slot 40 is smaller than that of the conventional one, and the same effects as those of the fourth embodiment can be obtained in this embodiment.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications are possible. In the first to third embodiments, the strip steel plate 23 is used.
Is plastically deformed into an annular shape, and the stator core 13 is configured by winding the annular portion while laminating it.
Instead of this, as in the fourth and fifth embodiments, an annular body may be formed from a strip-shaped steel plate, and the annular body may be laminated to form the stator core 13.

In the fourth and fifth embodiments, instead of forming the stator core 13 by laminating the annular bodies 37 and 42, the stator core 13 is formed longer as in the first and second embodiments. The stator steel core 13 may be configured by making the band-shaped steel plate thus formed into an annular shape, and continuously winding and laminating the annular portion. Moreover, the strip-shaped steel plates 36 and 41 are laminated,
It is also possible to form the stator core 13 by plastically deforming the laminated steel plate in an annular shape. In addition, the long overhang 39
The a and 45a and the short overhang portions 39b and 45b may be laminated every other layer.

Further, instead of providing the long projecting portions 39a, 45a and the short projecting portions 39b, 45b on the projecting pieces 39, 44, projecting portions having the same width dimension are provided, and at least one projecting portion is provided. The layers may be laminated so as to be shifted to both sides in the circumferential direction for each layer. Also in this case, the intended purpose of reducing the width of the opening of the slot can be achieved.

[0046]

As is clear from the above description, according to the present invention, the belt-shaped steel plate is plastically deformed in an annular shape, and the stator core of the external rotation type motor is formed by winding and laminating the annular portion. Even with this, the width dimension of the opening of the slot can be reduced, so that the cogging torque can be reduced, and the rotation unevenness and vibration noise of the motor can be reduced. Further, by adjusting the overlapping dimension of the projecting portion of the protruding piece portion of the strip-shaped steel plate, an excellent practical effect that the width dimension of the opening of the slot can be appropriately adjusted can be obtained.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention, and is a plan view showing a part of a strip-shaped steel plate.

FIG. 2 is a plan view showing a part of a stator core and a rotor.

FIG. 3 is a longitudinal sectional view showing the entire configuration of the motor.

FIG. 4 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 5 is a plan view showing a part of a stator core and a permanent magnet.

FIG. 6 shows a third embodiment of the present invention, and is a view corresponding to FIG.

FIG. 7 is a plan view of a stator core according to a fourth embodiment of the present invention.

FIG. 8 is a view of the teeth head viewed from the outer peripheral side.

FIG. 9 is a plan view of a strip steel plate.

FIG. 10 is a plan view of an annular body.

FIG. 11 shows a fifth embodiment of the present invention, and is a view corresponding to FIG. 7;

FIG. 12 is a diagram corresponding to FIG. 8;

FIG. 13 is a diagram corresponding to FIG. 9;

FIG. 14 is a diagram corresponding to FIG. 10;

FIG. 15 shows a conventional example, and is a partial plan view of a strip-shaped steel sheet before plastic deformation (a), and a partial plan view of a strip-shaped steel sheet after plastic deformation (b).

[Explanation of symbols]

In the figure, 13 is a stator core, 20 is a tooth, 23, 3
6, 41 are strip-shaped steel plates, 25, 39, 44 are protruding pieces, 26
a, 26b, 33, 34, 39a, 39b, 45a, 4
5b indicates an overhang portion.

Claims (6)

[Claims] 1. A belt-shaped steel plate having substantially T-shaped teeth having projecting portions formed at substantially equal intervals and having a protruding portion at a front end thereof is formed into an annular shape such that the projecting portions are on the outer peripheral side. In the stator core of the external rotation type motor formed by laminating the annular portions, the projecting portions of the adjacent protruding pieces of the strip-shaped steel plate are configured to overlap in the width direction of the strip-shaped steel plate. A stator core for an epicyclic motor. 2. The overhanging portion has a long overhanging portion and a short overhanging portion, and the protruding portion having the long overhanging portion and the protruding portion having the short overhanging portion are provided alternately. The stator core of the external rotation type motor according to claim 1. 3. The stator core of an external rotation type motor according to claim 2, wherein an outer peripheral surface of the long overhang portion is located inside an outer peripheral surface of the short overhang portion. 4. The shape of the projecting portion of the projecting piece of the strip-shaped steel sheet is such that a gap is formed between the projecting portions of the adjacent projecting pieces when the strip-shaped steel sheet is plastically deformed in a ring shape. 4. A stator core for an external rotation type motor according to claim 1, wherein the stator core is configured as follows. 5. A belt-shaped steel plate having teeth formed at substantially equal intervals and having substantially T-shaped protruding portions formed at substantially distal ends, and formed into an annular shape such that the protruding portions are on the outer peripheral side. In the stator core of the external rotation type motor formed by laminating the annular portions while being deformed, the overhanging portion has a long overhanging portion and a short overhanging portion, and the projecting portion having the long overhanging portion And the protruding piece portion having the short overhang portion are provided alternately, and when laminating the strip-shaped steel plates, the teeth are configured by stacking the long overhang portion and the short overhang portion. A stator core for an epicyclic motor. 6. A belt-shaped steel plate having teeth formed at substantially equal intervals and having substantially T-shaped teeth having a projecting portion at a tip end thereof is formed into an annular shape so that the projections are on the outer peripheral side. In the stator iron core of the external rotation type motor formed by laminating the annular portions, one of the protruding portions of each protruding piece portion of the strip-shaped steel plate is configured to be longer and the other is configured to be shorter, and the annular plastic portion is formed. A stator core for an external rotation type motor, wherein the teeth are formed by stacking a long overhang portion and a short overhang portion when stacking the deformed annular portions.