JP2003088012A - Core sheet, manufacturing method therefor, stator, and motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core sheet which is used in a stator for use in motors and is manufactured at low cost, a manufacturing method for the core sheet, a stator, and a motor which is manufactured at low cost and allows the enhancement of output and the reduction in size. SOLUTION: A core sheet 10 comprises an annular outer core sheet 12; a plurality of core portions 14 which are installed on the inner circumferential surface of the outer core sheet 12 so that the core portions are radially protruded inward in the radial direction; and bridging portions 16 which join the ends of a plurality of the core portions 14 located inside in the radial direction. A concave curved portion 16a which is thinner than the other portions of the core sheet 10 and runs in the circumferential direction is formed in each bridging portion 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core sheet, a method of manufacturing the core sheet, a stator, and an electric motor, and more particularly, a core sheet in which inner ends of iron core portions to which windings are applied are connected, and a method of manufacturing the same. The present invention relates to a stator formed by laminating the core sheets and an electric motor using the stator.

[0002]

2. Description of the Related Art In an electric motor, for example, a rotating magnetic field type electric motor such as a brushless motor, a plurality of iron core portions formed on a stator are provided with windings, and a current is passed through the windings to generate a rotating magnetic field. As a result, the rotor with magnet arranged inside the stator is rotated.

Such a stator of a rotating magnetic field type motor has a core made of a thin magnetic material such as a silicon steel plate whose surface is subjected to an insulation treatment such as an insulating film in order to prevent power loss and heat generation due to an eddy current. It is formed by stacking sheets.

FIG. 8 shows a stator 30 formed by laminating core sheets 10 according to a conventional example. Core sheet 1
0 is the outer core sheet 12 formed in a ring shape
And an inner core sheet 13 located inside the outer core sheet 12.

The inner core sheet 13 is composed of a plurality of iron core portions 14 which are winding axes of windings and a ring-shaped bridging portion 16, and the iron core portion 14 is outside the ring-shaped bridging portion 16. Are continuously formed in a radial direction from the outside to the outside in the radial direction. That is, the plurality of iron core parts 14 are radially integrally formed by the bridging part 16.

A dovetail-shaped engaging portion 14a is formed at the outer end of the iron core portion 14 in the radial direction.
The outer core sheet 12 is fitted with a fitting portion 12a provided on the inner side in the radial direction, and the outer core 12 and the inner core 13 are integrally fixed (see Japanese Patent No. 2875497).

The outer core sheet 12 and the inner core sheet 13 can be mass-produced by pressing or the like. In addition, the inner core sheet 13 has slots 18 for winding, that is, the adjacent iron core portions 1.
Since the space between the four openings opens outward in the radial direction, there are advantages that the winding is easy and the winding process at the time of manufacturing the motor can be automated.

However, in the stator 30 formed by laminating the core sheets 10, the iron core portion 14 is coupled by the bridging portion 16, so that a part of the magnetic flux becomes a leakage magnetic flux and the bridging portion 16 is connected. As it flows, this leakage flux does not affect the rotation of the rotor. Therefore, it is necessary to generate an effective magnetic flux to compensate for this loss, which hinders downsizing of the electric motor and high output.

Therefore, in the core sheet 10 of FIG.
As shown in, the thickness of the bridging portion 16 is thinner than the thickness of other portions of the core sheet 10. Therefore, in the stator 30 formed by stacking the core sheets 10, the substantial thickness of the bridging portion 16 in the axial direction is determined by the thickness of the bridging portion 16 and the thickness of other portions of the core sheet 10. It will be reduced according to the ratio.

The magnetic resistance of a magnetic material such as the stator 30 is inversely proportional to the size of the effective sectional area of the magnetic path through which the magnetic flux flows. Therefore, in the stator 30, since the effective thickness of the bridging portion 16 in the axial direction is reduced, the effective cross-sectional area in this portion is reduced as compared with the other portions, so that the bridging portion 16 is reduced. Magnetic resistance is stator 30
Is increased over other parts of.

As a result, the leakage flux can be reduced and the effective flux can be increased, so that the efficiency of the electric motor can be improved.

The core sheet 10 is easily formed by pressing a thin metal plate. In addition,
The bridging portion 16 formed to be thinner than the other parts of the core sheet 10 can be thinned by performing compression processing with a pressing die when molding the core sheet 10.

[0013]

However, when molding the core sheet 10 having a thin portion, when the thin portion is a flat surface like the bridging portion 16 shown in FIG. Since the pressure is distributed over the entire plane, it is necessary to increase the applied pressure, and a press machine having a large pressurizing ability is required. In addition, the wear of the pressing die is accelerated, the life of the pressing die is shortened, and the core sheet 10
Was a cause of increasing the manufacturing cost of.

In view of the above problems, an object of the present invention is to provide a core sheet used for a stator used in an electric motor, which can be manufactured at low cost, and a method for manufacturing the core sheet. To do.

It is another object of the present invention to provide a stator which can be manufactured at a low cost and an electric motor which can be increased in output and downsized.

[0016]

According to the core sheet of the first aspect, the above-mentioned problem is that the outer core sheet has an annular shape, and the inner peripheral surface of the outer core sheet is radially radially inward. A plurality of iron core portions provided so as to project,
A core sheet consisting of a bridging portion connecting the radially inner ends of the plurality of iron core portions to each other, wherein the bridging portion is thinner than the plate thickness of other portions of the core sheet, And it is solved by forming the concave curved surface along the circumferential direction.

Since the bridge portion is formed with a groove having a concave curved surface, the bridge portion is thinner than other portions of the core sheet. However, the bridge portion is thinner than the flat portion. Also, the bridge portion is hard to bend, and the core sheet can be handled stably.

Further, according to the method for manufacturing a core sheet of the present invention, the above-mentioned problem is that the outer core sheet having an annular shape and the inner peripheral surface of the outer core sheet are radially protruded radially inward. A plurality of iron core parts provided as
A method of manufacturing a core sheet, comprising: a bridging portion connecting end portions of the plurality of iron core portions in a radial direction to each other,
A temporary punching step of punching the vicinity of the bridge portion in the radial direction from the thin metal plate and the vicinity of the outside, and after the temporary punching step, the bridge portion is pressed by a pressing die with a curved tip. After the bridge portion pressing step of crushing and the bridge portion pressing step,
This is solved by providing a step of punching the inside and outside of the portion corresponding to the bridging portion in the radial direction and punching into the final shape.

The portion corresponding to the bridging portion is thinned by being crushed by the pressing die having a curved end, so that the pressing die effectively applies the pressing force to the bridging portion of the thin metal plate. It is possible to concentrate on a considerable portion, the pressing force can be made smaller than when the tip of the pressing die is flat, and the tip portion of the pressing die is less likely to wear, and as a result, the manufacturing cost of the core sheet Can be suppressed.

Further, according to the stator of the third aspect, the above-mentioned problem is provided in the annular outer core sheet and on the inner peripheral surface of the outer core sheet so as to radially protrude inward in the radial direction. A plurality of iron core portions, and a bridging portion that connects the radially inner ends of the plurality of iron core portions to each other,
A core sheet made of a plurality of laminated core sheets, wherein the bridging portion has a concave curved surface that is thinner than the plate thickness of the other portion of the core sheet and that extends along the circumferential direction. It can be solved by being formed.

Since the bridging portion of the core sheet that constitutes the stator is thinned, the bridging portion of the stator as a whole is substantially thinner than the other portions. Therefore, since the effective cross-sectional area of the bridging portion is reduced, the magnetic resistance is increased, and as a result, the effective magnetic flux flowing through the iron core portion can be increased.

According to another aspect of the present invention, there is provided an electric motor including at least a rotor and a stator formed by laminating core sheets, wherein the core sheets are circular. A ring-shaped outer core sheet, a plurality of iron core portions provided on the inner peripheral surface of the outer core sheet so as to radially protrude toward the inner side in the radial direction, and the end portions on the inner side in the radial direction of the plurality of iron core portions. The bridging portion is connected to each other, and the bridging portion is formed by forming a concave curved surface that is thinner than the plate thickness of the other portion of the core sheet and extends along the circumferential direction.

Since the stator of the electric motor is constructed so that the effective cross-sectional area of the bridging portion is small, the magnetic resistance in the bridging portion is large, and as a result, the effective magnetic flux flowing through the iron core portion is increased. be able to. Therefore, it is possible to obtain the electric motor in which the magnetic flux efficiently acts on the rotation of the rotor.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings, taking a brushless motor 1 as an example. The same elements as those of the conventional example will be described with the same reference numerals. Further, the arrangement, shape, etc. described below are not intended to limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.

FIG. 1 is a sectional view of the brushless motor of the embodiment, FIG. 2 is a sectional view of the stator and rotor of FIG. 1, FIG. 3 is a partially enlarged view of the inter-core of the embodiment, and FIGS. 4 and 5 are of the embodiment. FIG. 6 is an explanatory view of the manufacturing process of the core sheet, FIG. 6 is a front view of the inner core sheet and the outer core sheet, and FIG. 7 is an explanatory view of the manufacturing process of the core sheet of another embodiment.

The structure of the brushless motor 1 according to the embodiment of the present invention will be described with reference to FIG. Brushless motor 1
Is a rotor 2 rotatably supported by bearings 41, 42.
0, a stator 30 having a winding 32, and a yoke housing 40 that houses the rotor 20 and the stator 30.

The stator 30 can generate a rotating magnetic field for rotating the rotor 20 by causing a current to flow through the winding 32 from an external power supply device (not shown).

Although not shown, the brushless motor 1 is provided with a well-known position detector including a Hall element, a rectifying element, a position detecting magnet, and the like, and a control circuit. Position detection is performed during rotation of the. A desired pulse current is applied to the winding 32 from the control circuit based on the signal obtained by the position detection and the speed setting value, so that the rotor 20 can rotate stably.

FIG. 2 shows a sectional view of the rotor 20 and the stator 30. However, the illustration of the winding 32 is omitted for easy understanding. In the rotor 20, the shaft 22 is attached to a cylindrical back yoke 22a, and the back yoke 22a
A plurality of magnets 21 having different magnetic poles are arranged adjacent to each other on the outer periphery of the.

The stator 30 is formed by coaxially stacking a plurality of core sheets 10. These core sheets 10 are made of a thin magnetic material such as a silicon steel plate whose surface is provided with an insulating film (not shown). The core sheet 10 includes a ring-shaped outer core sheet 12 and an inner core sheet 13. Outer core sheet 12
The fitting portion 12a and the cutout portion 12 are provided at predetermined intervals on the inner peripheral surface of the
b are formed alternately.

Further, the core sheet 10 is provided with a plurality of iron core portions 14. These iron core portions 14 are provided inside the outer core sheet 12, and are radially arranged inward in the radial direction. These iron cores 1
4 has a dovetail-shaped engaging portion 14 at the outer end in the radial direction.
a is formed, the engaging portion 14a is fitted to the fitting portion 12a of the outer core sheet 12, and the outer core sheet 12 and the inner core sheet 13 are integrally fixed.

On the other hand, at the radially inner ends of the iron core portions 14, the adjacent iron core portions 14 are bridged by the bridging portions 16 respectively.
Are integrally connected to each other, and therefore, the radially inner end portion of the iron core portion 14 and the bridging portion 16 are formed in a ring shape as a whole.

As shown in FIG. 3, these bridging portions 16 have concave curved surface portions 16a formed on the upper surface side of the core sheet 10. The concave curved surface portion 16a is formed so that the inner surface has a curved shape.

Since the stator 30 is formed by laminating the core sheets 10 as described above, the portion of the stator 30 corresponding to the bridging portion 16 is intermittently thinned in the axial direction. Has become. Therefore, the substantial thickness of this portion is smaller than the substantial thickness of other portions of the stator 30.

Since the magnetic resistance is inversely proportional to the size of the effective sectional area of the magnetic path through which the magnetic flux flows, the bridging portion 1 of the stator 30 is
The magnetic resistance of the portion corresponding to 6 is larger than that of the other portions. Therefore, when the brushless motor 1 operates, the leakage magnetic flux leaking to the bridging portion 16 decreases, and the effective magnetic flux flowing in the iron core portion 14 can be increased.

Next, a method of manufacturing the core sheet 10 will be described. The core sheet 10 is formed by pressing a thin metal plate 70. FIG. 4 shows a processed state of the thin metal plate 70 for forming the core sheet. The hatched portion in FIG. 4 represents a portion punched by press working. Also, FIG.
FIG. 4 is a sectional view of the press die.

First, as shown in FIG. 5, a thin metal plate 70 is placed on a die plate 52 provided on a die base 51 of a punching progressive die 50, and a temporary punching punch 61,
The stripper plate 53 including the pressing punch 62, the slot punching punch 63, the central punching punch 64, the outer frame punching punch (not shown), and the die cutting punch is positioned, and the thin metal plate 70 is moved by a predetermined length. Perform punching.

The temporary punching punch 61, the pressing punch 62, the slot punching punch 63, the central punching punch 64, the outer frame punching punch, and the die plate 52 corresponding to the die punching die are located at the die plate 52 side, respectively. , 6
8 etc. are arranged.

As shown in FIG. 5A, in the temporary punching step, the outer peripheral portion and the inner peripheral portion of the bridging portion 16 of the core sheet 10 are punched by the temporary punching punches 61a and 61b, respectively. By the temporary punching process, two temporary punching holes are radially formed in the thin metal plate 70 as shown in FIG. The length of the temporary punching hole in the longitudinal direction is substantially equal to the length of the bridging portion 16 of the core sheet 10 in the circumferential direction.

Next, as shown in FIG. 5B, in the bridging portion pressing step, the central portion between the two temporary punching holes formed in the temporary punching step is pressed by the pressing punch 62. The pressing punch 62 is a pressing die having a rectangular cross section whose one side is equal to the circumferential length of the bridging portion 16 of the core sheet 10, and the longitudinal cross section of the tip end portion in the radial direction of the molded core sheet 10 is curved. Has become.

By the bridging portion pressing step, the pressing punch 62 presses the central portions of the two provisionally punched holes radially formed as shown in FIG. 4B. The pressed portion of the thin metal plate 70 corresponding to the bridging portion 16 is deformed and extruded in the direction of the two temporary punching holes as shown in FIG. 5 (B).

Then, as shown in FIGS. 5C and 4C, in the slot punching step, the slot 18 of the core sheet 10 is moved by the slot punching punch 63.
The corresponding portion and the portion corresponding to the fitting portion 12a of the outer core sheet 12 are punched. At this time, in the bridging portion pressing step, the portion protruding in the outer temporary punching hole direction is also cut.

Further, as shown in FIGS. 5D and 4D, in the center punching step, the center punching punch 6 is used.
4, the inner circular hole of the inner core sheet 13 of the core sheet 10 is punched out. At this time, in the bridging portion pressing step, the portion protruding in the inner temporary punching hole direction is also cut.

Then, as shown in FIG. 4 (e), in the outer frame punching step, the outer peripheral punching punch punches the portion corresponding to the outer periphery of the inner core sheet 13 to show the result in FIG. 6 (A). The inner core sheet 13 is formed and punched from the thin metal plate 70.

Then, as shown in FIG. 4 (f), in the die-cutting step, a portion corresponding to the outer periphery of the outer core sheet 12 is punched out by the die-cutting punch, so that FIG.
The outer core sheet 12 shown in (B) is formed and punched from the thin metal plate 70.

A plurality of fitting portions 12a and the same number of notches 12b as the fitting portions 12a are formed on the inner peripheral portion of the outer core sheet 12 molded as described above. When the similarly laminated inner core sheet 13 is press-fitted and fixed to the laminated outer core sheet 12, the fitting portion 12a of the outer core sheet 12 and the engagement portion 14a of the inner core sheet 13 can be fitted to each other. The outer shape of the engaging portion 14a (that is, the inner shape of the cutout portion 12b) is larger than the inner shape of the fitting portion 12a by the press-fitting margin.

The formed outer core sheet 12 and inner core sheet 13 are laminated and integrated with each other. At this time, the inner core sheet 13 is coaxially laminated so that the sides on which the concave curved surface portions 16a are formed face the same direction. Concave curved surface portion 16 of the inner core sheet 13
By stacking so that a is on the same side, the thinned bridge portions 16 are not continuous in the axial direction, and the thinned portions are arranged intermittently and evenly in the axial direction. Leakage magnetic flux between 16 can be prevented.

Further, the integrated inner core sheet 13 is provided with windings 32. Then, the fitting portion 12a of the outer core sheet 12 and the engaging portion 14a of the inner core sheet 13 which are integrated are fitted to each other, and the outer core sheet 12 and the inner core sheet 13 are integrally fixed.

As described above, according to this embodiment,
It has the following effects. (1) In the core sheet 10 in which the radially inner end of the iron core portion 14 to which the winding 32 is applied is connected by the bridging portion 16, the bridging portion 16 has a concave curved surface portion 1 whose inner surface is curved.
Since 6a is formed in the circumferential direction, the bridge portion 16
Since the cross-sectional area of the bridge is small, the magnetic resistance in the bridge portion 16 is large.

Therefore, the brushless motor 1 manufactured by using the core sheet 10 has the bridging portion 16 at the time of operation.
The efficiency is improved because the leakage flux flowing through is reduced.

(2) Further, even in the core sheet 10 formed of the thin metal plate 70, the bridge portion 16 has the concave curved surface portion 16a having the curved inner surface, and therefore the bridge portion 1
6 is less likely to bend, and the core sheet 10 is stably handled.

(3) Conventionally, in order to reduce the thickness of the bridging portion 16, a pressing die having a flat tip surface was used, but the bridging portion 16 of the core sheet 10 according to the embodiment of the present invention is thin. For this purpose, since the pressing punch 62 whose tip surface is a curved pressing type is used, the pressing force is concentrated on the thin metal plate 70 from the tip end of the pressing die whose curved front surface is a curved shape, and efficiently. Thus, the bridging portion 16 can be formed with a smaller pressing force than the conventional one.

The embodiment of the present invention may be modified as follows. In the above-described embodiment, the vertical section of the tip portion of the pressing punch 62 in the radial direction of the core sheet 10 has a curved surface shape, but it may have a V-shaped vertical section in which the distal end portion has a curved surface.

Further, as shown in FIG. 7 (A), the pressing punch 62 may have a flat surface portion 62b provided on the tip end surface thereof, and a curved surface-shaped convex portion 62a provided on the flat surface portion 62b. After the temporary punching step, when the portion corresponding to the bridging portion 16 of the thin metal plate 70 is pressed by the pressing punch 62 having the curved convex portion 62a in the bridging portion pressing step, the curved convex portion 62a causes The portion corresponding to the concave curved surface portion 16a of the bridge portion 16 is formed. The thin metal plate 70 is deformed by being pressed by the convex portion 62a having a curved surface shape, and the portion protruding from the concave curved surface portion 16a corresponding portion can have a flat upper surface by the flat surface portion 62b.

Then, as shown in FIG. 7B, on the stripper plate 53 side in the slot punching process,
A convex pressing portion 53a that fits into a portion corresponding to the concave curved surface portion 16a formed in the bridging portion pressing step is provided. With this configuration, in the slot punching process, the slot 18 of the core sheet 10 is removed by the slot punching punch 63.
When the corresponding portion is punched out, it is possible to press the portion corresponding to the bridge portion 16 by the convex pressing portion 53a. Therefore, the portion protruding from the portion corresponding to the bridge portion 16 to the slot 18 side can be reliably cut.

Further, as shown in FIG. 7C, also on the stripper plate 53 side in the center punching step, a convex pressing portion 53b fitted into the concave curved surface portion 16a corresponding to the bridge curved portion pressing step formed in the bridging portion pressing step. Is provided. With this configuration, in the center punching step, when the center punching punch 64 punches the inner circular sheet corresponding portion of the inner core sheet 13 of the core sheet 10, the convex pressing portion 53b corresponds to the bridge portion 16 corresponding portion. Can be held down. Therefore, the portion protruding from the portion corresponding to the bridging portion 16 to the inner circular hole side of the inner core sheet 13 can be reliably cut.

In the above embodiment, the central punching process is performed after the slot punching process. However, the central punching process may be performed first, and then the slot punching process may be performed.

Further, in the above embodiment, the core sheet 10 is used.
Is a structure in which the outer core sheet 12 and the inner core sheet 13 can be separated, but the structure is not necessarily required to be separable, and the outer core sheet 12 and the inner core sheet 13 are formed integrally from the time of molding. Good. The above configuration is preferable because the outer frame punching step in the press working is unnecessary.

Further, although the stator 30 is applied to the brushless motor 1 in the above embodiment, the present invention is not limited to this, and the stator 30 may be replaced by another inner rotor type rotating magnetic field type motor,
For example, it may be applied to an induction motor. Also in this case, the reactive magnetic flux flowing through the bridge portion 16 is reduced, and the effective magnetic flux acting on the rotation of the rotor can be effectively increased.

Further, in the above embodiment, the outer core 1
Since the outer core 12 and the inner core 13 are molded in the same process, the outer core 12 has the notch 12b.
The notch 12b may not be formed in the outer core 12 by forming the outer core 12 by separate steps.

[0061]

As described above, according to the core sheet and the method for manufacturing the core sheet of the present invention, the core sheet used for the stator is easily formed from a thin metal plate by press working, so that the cost is low. It can be manufactured.

Further, since the bridging portion connecting the iron core portions of the core sheet is thinned by forming the concave groove having the curved inner surface, wear of the pressing die of the press machine is reduced. can do.

Further, according to the stator of the present invention, since the bridging portions connecting the iron core portions of the laminated core sheets constituting the stator are thinned, the effective breaking of the bridging portions of the stator is achieved. The area becomes smaller and the magnetic resistance, which is in inverse proportion to the effective area, becomes larger. Therefore, the leakage magnetic flux flowing through the bridging portion of the stator can be reduced, and the effective magnetic flux flowing through the iron core portion can be increased. Moreover, since the core sheet can be manufactured at low cost, the manufacturing cost of the stator can be reduced.

Further, according to the electric motor of the present invention, the stator formed by laminating the core sheets can be manufactured at low cost, and the manufacturing cost of the electric motor can be reduced.
Further, since the core sheet is used, the leakage magnetic flux at the bridging portion is reduced and the effective magnetic flux can be increased, so that high output and downsizing can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a brushless motor according to an embodiment.

2 is a cross-sectional view of the stator and rotor of FIG.

FIG. 3 is a partially enlarged view of the inner core of the embodiment.

FIG. 4 is an explanatory diagram of a manufacturing process of the core sheet of the example.

FIG. 5 is an explanatory diagram of a manufacturing process of the core sheet of the example.

FIG. 6 is a front view of an inner core sheet and an outer core sheet.

FIG. 7 is an explanatory diagram of a manufacturing process of a core sheet of another example.

FIG. 8 is a perspective view of a conventional stator.

FIG. 9 is a partially enlarged view of a conventional inner core sheet.

[Explanation of symbols]

1 brushless motor, 10 core sheet, 12
Outer core sheet, 12a fitting part, 12b notch part, 13 inner core sheet, 14 iron core part,
14a engaging part, 16 bridging part, 16a concave curved surface part, 18 slot, 20 rotor, 21 magnet, 22 shaft, 22a back yoke,
30 stator, 32 windings, 40 yoke housing, 50 punching progressive feed type, 51 type stand, 5
2 die plate, 53 stripper plate, 53
a, 53b Convex pressing part, 61 Temporary punching punch,
61a Temporary Punching Punch, 61b Temporary Punching Punch, 62 Pressing Punch, 62a Convex Part, 62b
Flat part, 63 slot punch, 64 central punch, 65, 66, 67, 68 die, 7
0 Thin metal plate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takanori Ozawa             Asumo Stock Association, 390 Umeda, Kosai City, Shizuoka Prefecture             In-house (72) Inventor Mitsuhiko Matsushita             Asumo Stock Association, 390 Umeda, Kosai City, Shizuoka Prefecture             In-house F-term (reference) 5H002 AA07 AB05 AB06 AE07 AE08                 5H615 AA01 BB14 PP01 PP07 PP10                       SS03 SS05 TT04

Claims (4)

[Claims] 1. An annular outer core sheet, a plurality of iron core portions radially provided on an inner peripheral surface of the outer core sheet so as to radially inward, and radii of the plurality of iron core portions. A bridging portion that connects the ends on the inner side in the direction to each other,
The core sheet having a concave curved surface that is thinner than the plate thickness of the other portion of the core sheet and that extends in the circumferential direction. 2. An annular outer core sheet, a plurality of iron core portions radially provided on an inner peripheral surface of the outer core sheet so as to radially inward, and radii of the plurality of iron core portions. A bridging portion that connects the ends on the inner side in the direction to each other,
A method of manufacturing a core sheet consisting of: a temporary punching step of punching a thin metal plate in the vicinity of the inner side and the outer side in the radial direction of the portion corresponding to the bridging portion, and after the temporary punching step, the portion corresponding to the bridging portion And a bridge portion pressing step of crushing the tip portion with a pressing die having a curved surface shape, after the bridge portion pressing step, punching the inside and outside in the radial direction of the bridge portion corresponding portion, and punching into the final shape And a method of manufacturing a core sheet, comprising: 3. An annular outer core sheet, a plurality of iron core portions radially provided on an inner peripheral surface of the outer core sheet so as to radially inward, and radii of the plurality of iron core portions. A bridging portion that connects the ends on the inner side in the direction to each other,
A stator formed by stacking a plurality of core sheets consisting of, wherein the bridging portion is thinner than the plate thickness of the other portion of the core sheet, and has a concave curved surface along the circumferential direction. A stator characterized by being formed. 4. An electric motor comprising at least a rotor and a stator formed by laminating core sheets, wherein the core sheets are an annular outer core sheet and an inner peripheral surface of the outer core sheet. A plurality of iron core portions provided to radially protrude inward in a radial direction, and a bridging portion that connects the radially inner ends of the plurality of iron core portions to each other, the bridging portion The electric motor is characterized in that a concave curved surface which is thinner than the plate thickness of the other portion of the core sheet and extends in the circumferential direction is formed on the.