JP2014007948A - Motor core, motor, transport device, and manufacturing method of motor core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor core improved in order to realize a motor and transport device which prevent efficiency deterioration due to a magnetic loss while maintaining smooth rotation.SOLUTION: In a motor core 1 formed by combining together an inner circumference core 2 and an outer circumferential core 3 which are separate bodies mutually, a cut out 5 penetrating in the radial direction is provided in the inner circumference core 2. Here, the cut out 5 may be provided in the inside in the axial direction with both axial end faces of the inner circumference core 2 left. In addition, the cut out 5 may be provided in a circumferential direction of the inner circumference core 2 at equal intervals. In addition, the inner circumference core 2 has two or more slot neck parts 21 directed to the outer diameter side radially, and the slot neck parts 21 are connected by a slot connecting part 22 in the inner circumference side, and the cut out 5 may be provided in the slot connecting part 22.

Description

  The present invention relates to a motor core used in a motor that drives, for example, an arm of a transfer device. Moreover, it is related with the motor provided with the motor core, and the conveying apparatus provided with the motor.

  2. Description of the Related Art Conventionally, in the manufacture of semiconductors, flat panel displays, and the like, there is a transfer device including an arm that can move a workpiece even in a vacuum. The drive source of this transport device is generally a motor, and a servo motor is used. In addition, a direct drive motor that does not require a reduction gear is also used for downsizing the device.

  As a motor core used in this motor, a two-part motor core composed of an inner peripheral core and an outer peripheral core is known. Patent Document 1 discloses a motor core that can suppress a decrease in generated torque of a motor and reduce heat generation of the motor even when a two-divided motor core is used. This motor core is a combination of a non-oriented electrical steel sheet and a directional electrical steel sheet.

JP 2010-259246 A

  In recent years, limited resources such as oil have been saved and conversion to natural energy has been promoted. On the other hand, in various product factories, energy saving that suppresses power consumption without impairing functions is desired. In particular, motors are widely used in various machines, and further efficiency and power saving of motors are required in various product factories.

  An object of the present invention is to prevent efficiency deterioration due to magnetic loss while maintaining smooth rotation in a motor.

(1) A motor core comprising an inner core and an outer core that are separate from each other, wherein the inner core or the outer core is provided with a notch penetrating in the radial direction.
(2) The motor core according to (1), wherein the notch is provided on a rotor side of the inner core and the outer core.
(3) The motor core according to (1) or (2), wherein the notch is provided inside the axial direction, leaving both end faces in the axial direction of the inner peripheral core or the outer peripheral core.
(4) The motor core according to (1) or (3), wherein the notches are provided at equal intervals in a circumferential direction of the inner peripheral core or the outer peripheral core.
(5) The inner peripheral core has a plurality of slot necks radially extending toward the outer diameter side, the slot necks are connected by a slot connecting portion on the inner peripheral side, and the notch is provided in the slot connecting portion. The motor core according to any one of (1) to (4), wherein
(6) The slot neck portion of the inner peripheral core has a concave portion or a convex portion at an outer peripheral side tip, and the concave portion or the convex portion is fitted into a convex portion or a concave portion provided on the inner periphery of the outer peripheral core. The motor core according to any one of (1) to (5), wherein the inner peripheral core and the outer peripheral core are not rotatable relative to each other.
(7) A plurality of motor windings wound beforehand on a bobbin are inserted into the inner peripheral core from the outer peripheral side, and the inner peripheral core in that state is inserted into the outer peripheral core in the axial direction. The motor core according to (1) to (6).
(8) The motor core according to any one of (1) to (7), wherein the notch has a linear shape that is long in an axial direction of the inner peripheral core or the outer peripheral core.
(9) The motor core according to any one of (1) to (7), wherein the notch is a rectangle that is long in an axial direction of the inner peripheral core or the outer peripheral core.
(10) The motor core according to any one of (1) to (7), wherein the notch is an ellipse that is long in an axial direction of the inner peripheral core or the outer peripheral core.
(11) The motor core according to any one of (7) to (10), wherein the notch has a longitudinal direction inclined from an axial direction of the inner peripheral core or the outer peripheral core to further reduce cogging torque. .
(12) The motor core according to any one of (2) to (11), wherein the notch is provided in a range of 70 to 90% of an axial width of the inner peripheral core or the outer peripheral core.
(13) A motor comprising the motor core according to (1) to (12).
(14) A transport device including the motor according to (13).
(15) In the manufacturing method of the motor core formed by combining the inner peripheral core and the outer peripheral core, which are separate from each other, the inner peripheral core or the outer peripheral core is formed into a desired annular shape from a magnetic steel sheet by pressing, and a plurality of the cores are formed. A manufacturing method of a motor core, characterized in that a notch is provided by post-processing on a peripheral surface of an inner peripheral core or the outer peripheral core that is laminated and bonded to each other.
(16) The motor core manufacturing method according to (15), wherein the notch is provided by laser cutting.
(17) A plurality of motor windings previously wound on a bobbin are inserted into the inner peripheral core obtained by the manufacturing method according to (15) or (16) from the outer peripheral side, and the inner peripheral core in that state is inserted into the inner peripheral core. A method for manufacturing a motor core, wherein the motor core is inserted into an outer core in the axial direction.
(18) An outer diameter of the inner peripheral core is set to a diameter equal to or smaller than an inner diameter of the outer peripheral core, and the inner peripheral core is bonded to the outer peripheral core after the inner peripheral core is inserted into the outer peripheral core. The method for manufacturing a motor core according to (17).
(19) The motor core manufacturing method according to (17), wherein an inner diameter of the outer peripheral core is set to be slightly smaller than an outer diameter of the inner peripheral core, and the inner peripheral core and the outer peripheral core are shrink-fitted. Method.

  According to the present invention, a motor with less deterioration in efficiency due to magnetic loss while maintaining smooth rotation is provided.

It is a figure which shows the motor core of 1st Embodiment. (A) is a front view, (b) is sectional drawing. It is a front view which shows the inner peripheral core of 1st Embodiment. It is a front view which shows the outer periphery core of 1st Embodiment. It is a figure which shows the Example of a linear notch. It is a figure which shows the Example of the notch which inclined the rectangle. It is a figure which shows the Example of the notch of an ellipse. It is a figure which shows the motor core of 2nd Embodiment. (A) is a front view, (b) is a side view. It is a front view which shows the inner peripheral core of 2nd Embodiment. It is a front view which shows the outer periphery core of 2nd Embodiment.

  Hereinafter, the present invention will be described in more detail with reference to the drawings with reference to embodiments for carrying out the invention (hereinafter referred to as embodiments). In addition, this invention is not limited at all by this embodiment. In addition, constituent elements in the following description include those that are substantially the same as those that can be assumed by those skilled in the art, that is, those in an equivalent range.

(First embodiment)
FIG. 1 is a diagram illustrating a motor core according to the first embodiment. (A) is a front view, (b) is sectional drawing. The motor (not shown) has a structure in which a rotor (rotor, not shown) rotates with respect to a stator (stator, not shown), and the motor core 1 constitutes a part of the stator. Yes. A rotor is provided on the inner peripheral side of the motor core 1 and is supported rotatably with respect to the stator. A plurality of permanent magnets are fixed in the circumferential direction on the outer peripheral side of the rotor, and the rotor is given rotational torque by the magnetic field generated by the motor core 1.

  The motor core 1 is applied to a direct drive motor among servo motors, and a large number of motor windings 4 are provided with 30 pieces. In general, a direct drive motor is a motor that can directly move and position a driven object without using a mechanism such as a speed reducer, and is provided with a large number of motor windings 4 in order to improve its positioning accuracy and driving torque. . The motor winding 4 is connected to a control unit (not shown) via a motor lead wire 6 and passes a current flowing from the control unit. The motor winding 4 generates a magnetic field by the principle of a solenoid, gives an attractive force and a repulsive force to the permanent magnet of the rotor, and gives a rotational torque to the rotor.

  The motor core 1 is formed by combining an inner peripheral core 2 and an outer peripheral core 3 which are separate from each other, and the inner peripheral core 2 is provided with a notch 5 penetrating in the radial direction. The notch 5 is provided in the inner peripheral core 2 and the outer peripheral core 3 on the rotor (permanent magnet) side, and is provided in the inner peripheral core 2 in the present embodiment. The notch 5 is provided in the axial direction inside, leaving both axial end surfaces of the inner peripheral core 2. The notches 5 are provided at equal intervals in the circumferential direction of the inner peripheral core 2.

  FIG. 2 is a front view showing the inner peripheral core 2. The inner peripheral core 2 has a plurality of slot neck portions 21 that radially extend toward the outer diameter side, and the slot neck portions 21 are connected by slot connecting portions 22 on the inner peripheral side. The slot connection portion 22 is provided with a notch 5. The slot neck portion 21 of the inner peripheral core 2 has a recess 23 at the outer peripheral end.

  FIG. 3 is a front view showing the outer peripheral core 3. The outer peripheral core 3 has an annular shape having a larger diameter than the inner peripheral core 2, and has convex portions 31 at equal intervals in the circumferential direction on the inner periphery. The convex portion 31 is fitted into the concave portion 23 of the inner peripheral core 2 so that the inner peripheral core 2 and the outer peripheral core 3 are not relatively rotatable.

  The motor core 1 has a structure in which a plurality of motor windings 4 wound beforehand on a bobbin are inserted into the slot neck portion 21 of the inner peripheral core 2 from the outer peripheral side, and the inner peripheral core in this state is inserted into the outer peripheral core 3 in the axial direction. It has become. As a result, the bobbin can be wound externally, and the space factor can be greatly improved.

  FIG. 4 is a view showing an embodiment of a linear (thin rectangular) cutout 51, which corresponds to an enlarged position of A of the inner peripheral core 2 shown in FIG. 1 (b). The inner peripheral core 2 is provided with a linear notch 51 that is long in the axial direction. The width of the notch 51 can be set by the laser cut width when the notch 51 is provided by laser cutting. In this embodiment, the longitudinal direction of the notch 51 and the axial direction D of the inner peripheral core 2 coincide with each other, but the longitudinal direction of the notch 51 may be inclined from the axial direction D of the inner peripheral core 2.

  FIG. 5 is a view showing an embodiment of a notch 52 having an inclined rectangular shape, which is an enlarged view of the position A of the inner peripheral core 2 shown in FIG. The inner peripheral core 2 is provided with a rectangular notch 52 that is long in the axial direction. In the present embodiment, the longitudinal direction L of the notch 52 is inclined from the axial direction D of the inner peripheral core 2. This has the effect of preventing a sudden change in magnetic flux and further reducing the cogging torque of the motor. However, even when the longitudinal direction L of the notch 52 and the axial direction D of the inner peripheral core 2 are matched, the efficiency of the motor, which is the subject of the present application, can be improved.

  FIG. 6 is a view showing an embodiment of the oval notch 53. Similar to FIGS. 4 and 5, this corresponds to an enlargement of the position A of the inner peripheral core 2 shown in FIG. The inner peripheral core 2 is provided with an elliptical cutout 53 that is long in the axial direction. As a result, stress concentration can be alleviated, and reduction in the cogging torque of the motor can be realized while suppressing a reduction in rigidity of the inner peripheral core 2. Although the strength of the inner peripheral core 2 is reduced by the notch 53, it becomes stronger to bend by having an elliptical shape. In the present embodiment, the longitudinal direction of the notch 53 coincides with the axial direction D of the inner peripheral core 2, but the longitudinal direction of the notch 53 may be inclined from the axial direction D of the inner peripheral core 2.

  In the embodiment of the shape of the various notches 51 to 53 shown in FIGS. 4 to 6, any notch is provided in a range of 70 to 90% of the axial width of the inner peripheral core 2. This is set in a well-balanced range because if it becomes less than 70%, magnetism leaks between the slots and loss increases, and if it exceeds 90%, the cogging torque of the motor increases.

  As described above, the motor includes the motor core 1 having the notch 5 in the inner peripheral core 2, whereby the motor can be made highly efficient with low magnetic loss while reducing the cogging torque.

  In addition, since the conveyance device including the motor including the motor core 1 as described above has a small cogging torque, the conveyance object can be conveyed with smooth rotation. In addition, since the magnetic loss of the motor is small, it is a highly efficient and power-saving transport device.

  Next, an embodiment of a method for manufacturing the motor core 1 will be described. In addition, this invention is not limited at all by this Example. In addition, the configuration procedures in the following description include substantially the same ones that can be assumed by those skilled in the art, so-called equivalent ranges.

  The manufacturing method of the motor core 1 according to the present embodiment is a manufacturing method of the motor core 1 that is formed by combining the inner peripheral core 2 and the outer peripheral core 3 which are separate from each other. A plurality of sheets are formed in an annular shape and bonded together, and a notch 5 is provided by post-processing on the inner peripheral surface of the inner peripheral core 2 in the stacked state.

  The notch 5 is provided by laser cutting. A plurality of motor windings 4 wound in advance on bobbins are inserted into the slot neck portion 21 of the inner peripheral core 2 from the outer peripheral side to the inner peripheral core 2 thus obtained, and the inner peripheral core 2 in this state is The core 3 is inserted in the axial direction. Thus, the space factor can be greatly improved by winding the bobbin externally.

  The outer diameter of the inner peripheral core 2 is set to be equal to or smaller than the inner diameter of the outer peripheral core 3, and after the inner peripheral core 2 is inserted into the outer peripheral core 3, the inner peripheral core 2 and the outer peripheral core 3 are bonded.

  As another embodiment, it is possible to set the inner diameter of the outer peripheral core 3 to be slightly smaller than the outer diameter of the inner peripheral core 2 and to shrink fit the inner peripheral core 2 and the outer peripheral core 3.

  In the first embodiment, the recess 23 is provided in the slot neck 21 of the inner peripheral core 2 and the protrusion 31 is provided in the inner periphery of the outer core 3. Conversely, the slot neck 21 of the inner core 2 is provided. A convex portion may be provided on the outer peripheral core 3 and a concave portion may be provided on the inner periphery of the outer peripheral core 3.

  In the first embodiment, an example in which the motor is an inner rotor (rotor is inside the stator) type has been described, but the present invention can also be applied to an outer rotor (rotor is outside the stator) type. In this case, the notch is provided in the outer core.

(Second Embodiment)
In the first embodiment, an example in which the motor is an inner rotor (the rotor is inside the stator) type (also referred to as an outer stator type) has been described, but in the second embodiment, the outer rotor (the rotor is outside the stator). An example of a mold (also referred to as an inner stator mold) will be described.
FIG. 7 is a diagram illustrating a motor core according to the second embodiment. (A) is a front view, (b) is a side view. A motor (not shown) has a structure in which a rotor (rotor, not shown) rotates with respect to a stator (stator, not shown), and a motor core 201 constitutes a part of the stator. Yes. A rotor is provided on the outer peripheral side of the motor core 201, and is supported rotatably with respect to the stator. A plurality of permanent magnets are fixed in the circumferential direction on the inner peripheral side of the rotor, and the rotor is given rotational torque by the magnetic field generated by the motor core 201.

  The motor core 201 is applied to a direct drive motor among servo motors, and is provided with a large number of motor windings 204 such as 30 pieces. In general, a direct drive motor is a motor that can directly move and position a driven object without using a mechanism such as a speed reducer, and includes a large number of motor windings 204 in order to improve its positioning accuracy and driving torque. . The motor winding 204 is connected to a control unit (not shown) via a motor lead wire (not shown), and passes a current flowing from the control unit. The motor winding 204 generates a magnetic field based on a solenoid principle, applies an attractive force and a repulsive force to the permanent magnet of the rotor, and applies a rotational torque to the rotor.

  The motor core 201 is formed by combining an inner peripheral core 202 and an outer peripheral core 203 which are separate from each other, and the outer core 203 is provided with a notch 205 penetrating in the radial direction. The notch 205 is provided on the inner core 202 and the outer core 203 on the rotor (permanent magnet) side, and is provided on the outer core 203 in the present embodiment. The notch 205 is provided on the inside in the axial direction, leaving both axial end surfaces of the outer core 203. The notches 205 are provided at equal intervals in the circumferential direction of the outer core 203.

  FIG. 8 is a front view showing the inner peripheral core 202. The inner peripheral core 202 has a plurality of slot neck portions 221 that radially extend toward the outer diameter side, and the slot neck portions 221 are connected by a slot connecting portion 222 on the inner peripheral side. The slot neck 221 of the inner peripheral core 202 has a recess 223 at the outer peripheral end.

  FIG. 9 is a front view showing the outer peripheral core 203. The outer peripheral core 203 has an annular shape whose diameter is larger than that of the inner peripheral core 202, and has convex portions 231 on the inner periphery at equal intervals in the circumferential direction. The convex portion 231 is fitted into the concave portion 223 of the inner peripheral core 202 so that the inner peripheral core 202 and the outer peripheral core 203 are not relatively rotatable. The outer core 203 is provided with the notch 205 described with reference to FIG.

  The motor core 201 has a structure in which a plurality of motor windings 204 wound beforehand on a bobbin are inserted into the slot neck portion 221 of the inner peripheral core 202 from the outer peripheral side, and the inner peripheral core in this state is inserted into the outer peripheral core 203 in the axial direction. It has become. As a result, the bobbin can be wound externally, and the space factor can be greatly improved. That is, even in the outer rotor type, the portion that divides the core is the outer periphery side of the motor winding 204 as in the inner rotor type described in the first embodiment, so that the motor wound with a larger number of turns. A winding 204 can be inserted.

The shape of the notch 205 is the same as that of the inner rotor type described in the first embodiment with reference to FIGS. 4, 5, and 6.
FIG. 4 is a view showing an embodiment of a linear (thin rectangular) cutout 51. The outer core 203 is provided with a linear notch 51 that is long in the axial direction. The width of the notch 51 can be set by the laser cut width when the notch 51 is provided by laser cutting. In this embodiment, the longitudinal direction of the notch 51 and the axial direction D of the outer peripheral core 203 coincide with each other, but the longitudinal direction of the notch 51 may be inclined from the axial direction D of the outer peripheral core 203.

  FIG. 5 is a view showing an embodiment of the notch 52 in which a rectangle is inclined. The outer core 203 is provided with a rectangular cutout 52 that is long in the axial direction. In the present embodiment, the longitudinal direction L of the notch 52 is inclined from the axial direction D of the outer core 203. This has the effect of preventing a sudden change in magnetic flux and further reducing the cogging torque of the motor. However, even when the longitudinal direction L of the notch 52 and the axial direction D of the outer core 203 are matched, the efficiency of the motor, which is the subject of the present application, can be improved.

  FIG. 6 is a view showing an embodiment of the oval notch 53. The outer peripheral core 203 is provided with an elliptical notch 53 that is long in the axial direction. As a result, stress concentration can be alleviated, and reduction in the cogging torque of the motor can be realized while suppressing reduction in rigidity of the outer peripheral core 203. Although the strength of the outer peripheral core 203 is reduced by the notch 53, it becomes stronger to bend by making an elliptical shape. In the present embodiment, the longitudinal direction of the notch 53 and the axial direction D of the outer core 203 coincide with each other, but the longitudinal direction of the notch 53 may be inclined from the axial direction D of the outer core 203.

  In the embodiment of the shape of the various notches 51 to 53 shown in FIGS. 4 to 6, any notch is provided in a range of 70 to 90% of the axial width of the outer core 203. This is set in a well-balanced range because if it becomes less than 70%, magnetism leaks between the slots and loss increases, and if it exceeds 90%, the cogging torque of the motor increases.

  As described above, since the motor includes the motor core 201 having the notch 205 in the outer peripheral core 203, the motor can be a highly efficient motor with low magnetic loss while reducing the cogging torque.

  Moreover, since the conveyance apparatus provided with the motor provided with the motor core 201 as described above has a small cogging torque, the conveyance object can be conveyed with smooth rotation. In addition, since the magnetic loss of the motor is small, it is a highly efficient and power-saving transport device.

  Next, an embodiment of a method for manufacturing the motor core 201 will be described. In addition, this invention is not limited at all by this Example. In addition, the configuration procedures in the following description include substantially the same ones that can be assumed by those skilled in the art, so-called equivalent ranges.

  The manufacturing method of the motor core 201 of the present embodiment is a manufacturing method of the motor core 201 that is a combination of the inner peripheral core 202 and the outer peripheral core 203 that are separate from each other. A plurality of sheets are laminated and bonded, and a notch 205 is provided by post-processing on the peripheral surface of the outer peripheral core 203 in the stacked state.

  The notch 205 is provided by laser cutting. A plurality of motor windings 204 wound beforehand on a bobbin are inserted into the inner peripheral core 202 from the outer peripheral side into the slot neck portion 221 of the inner peripheral core 202, and the inner peripheral core 202 in this state is axially inserted into the outer peripheral core 203. Insert into. Thus, the space factor can be greatly improved by winding the bobbin externally.

  The outer diameter of the inner peripheral core 202 is set to be equal to or smaller than the inner diameter of the outer peripheral core 203. After the inner peripheral core 202 is inserted into the outer peripheral core 203, the inner peripheral core 202 and the outer peripheral core 203 are bonded.

  As another example, it is possible to set the inner diameter of the outer peripheral core 203 to be slightly smaller than the outer diameter of the inner peripheral core 202 and to shrink-fit the inner peripheral core 202 and the outer peripheral core 203.

  Further, in the second embodiment, the recess 223 is provided in the slot neck 221 of the inner peripheral core 202 and the protrusion 231 is provided on the inner periphery of the outer core 203. Conversely, the slot neck 221 of the inner peripheral core 202 is provided. A convex portion may be provided on the outer peripheral core 203 and a concave portion may be provided on the inner periphery of the outer peripheral core 203.

1,201 Motor core 2,202 Inner peripheral core 21,221 Slot neck portion 22,222 Slot connecting portion 23,223 Concavity 3,203 Outer core 31,231 Convex portion 4,204 Motor winding 5, 51, 52, 53, 205 Notch 6 Motor lead wire D Axial direction L Notch longitudinal direction

Claims (19)

  A motor core comprising a combination of an inner peripheral core and an outer peripheral core which are separate from each other, wherein the inner peripheral core or the outer peripheral core is provided with a notch penetrating in the radial direction.   The motor core according to claim 1, wherein the notch is provided on a rotor side of the inner peripheral core and the outer peripheral core.   3. The motor core according to claim 1, wherein the notch is provided in the axial direction inside, leaving both axial end faces of the inner peripheral core or the outer peripheral core. 4.   The motor core according to claim 1, wherein the notches are provided at equal intervals in a circumferential direction of the inner peripheral core or the outer peripheral core.   The inner peripheral core has a plurality of slot necks radially extending toward the outer diameter side, the slot necks are connected by a slot connecting part on the inner peripheral side, and the notch is provided in the slot connecting part. The motor core according to claim 1, wherein:   The slot neck portion of the inner peripheral core has a concave portion or a convex portion at an outer peripheral end, and the concave portion or the convex portion is fitted into a convex portion or a concave portion provided on the inner periphery of the outer peripheral core, and The motor core according to claim 1, wherein the peripheral core and the outer peripheral core are not rotatable relative to each other.   A plurality of motor windings wound beforehand on a bobbin are inserted into the inner peripheral core from the outer peripheral side, and the inner peripheral core in this state is inserted in the outer core in the axial direction. The motor core as described in 1-6.   The motor core according to claim 1, wherein the notch has a linear shape that is long in an axial direction of the inner peripheral core or the outer peripheral core.   The motor core according to claim 1, wherein the notch is a rectangle that is long in an axial direction of the inner peripheral core or the outer peripheral core.   The motor core according to claim 1, wherein the notch is an ellipse that is long in an axial direction of the inner peripheral core or the outer peripheral core.   11. The motor core according to claim 7, wherein the notch has a longitudinal direction inclined from an axial direction of the inner peripheral core or the outer peripheral core to further reduce cogging torque.   The motor core according to claim 2, wherein the notch is provided in a range of 70 to 90% of an axial width of the inner peripheral core or the outer peripheral core.   A motor comprising the motor core according to claim 1.   A transport apparatus comprising the motor according to claim 13.   In the method for manufacturing a motor core comprising a combination of an inner core and an outer core, which are separate from each other, the inner core or the outer core is formed into a desired ring shape from a magnetic steel sheet by pressing, and a plurality of them are laminated and bonded. A method of manufacturing a motor core, wherein notches are provided in post-processing on the peripheral surface of the inner core or the outer core in the stacked state.   The method of manufacturing a motor core according to claim 15, wherein the notch is provided by laser cutting.   A plurality of motor windings previously wound on a bobbin are inserted into the inner peripheral core obtained by the manufacturing method according to claim 15 or 16 from the outer peripheral side, and the inner peripheral core in that state is inserted into the outer peripheral core. A method of manufacturing a motor core, wherein the motor core is inserted in a direction.   The outer diameter of the inner peripheral core is set to a diameter equal to or smaller than the inner diameter of the outer peripheral core, and the inner peripheral core is bonded to the outer peripheral core after the inner peripheral core is inserted into the outer peripheral core. Item 18. A method for manufacturing a motor core according to Item 17.   18. The method of manufacturing a motor core according to claim 17, wherein an inner diameter of the outer peripheral core is set to be slightly smaller than an outer diameter of the inner peripheral core, and the inner peripheral core and the outer peripheral core are shrink-fitted.

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