JP2019176560A - Stator core and motor - Google Patents

Abstract

To further reduce iron loss in a split stator structure.SOLUTION: A stator core 132 has a plurality of stator pieces 1, each having a yoke unit 10 having a first yoke surface, a second yoke surface opposite to the first yoke surface, a yoke outer wall unit extending from one side of the first yoke surface to one side of the second yoke surface, a yoke inner wall unit extending from one side of the first yoke surface to one side of the yoke second yoke surface so as to face the yoke outer wall unit, and a yoke side wall unit having a contact surface extending in a direction orthogonal to the first yoke surface and the second yoke surface from the yoke outer wall unit toward the yoke inner wall unit, and a teeth unit 20 extending from the yoke inner wall unit in a direction opposite to the yoke outer wall unit, disposed so that the contact surfaces are mutually in contact with each other. A ratio of a height of the contact surface to a height of the yoke side wall unit is 90% or more. Vickers hardness of the contact surface is more than 1 and 1.9 times or less of Vickers hardness of a magnetic steel sheet which is a material of the plurality of stator pieces.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a stator core and a motor.

  Various techniques for forming a stator core of a motor by laminating steel sheets subjected to various forming processes such as punching and shaving are known. For example, in Patent Document 1, shaving processing for removing a region corresponding to 5 to 25% of the plate thickness of the processed plate material is performed on the end surface subjected to the punching process once, and the thickness of the processed plate material is determined. A technique for removing regions corresponding to 40-60% is described. According to the technique described in Patent Document 1, a rotary electric iron core with a low iron loss can be obtained without annealing the rotary electric iron core by removing a region corresponding to a predetermined ratio with respect to the plate thickness of the plate material to be processed. Can be obtained. However, when the area corresponding to the predetermined ratio is removed, the yield must be slightly reduced.

  In Patent Document 2, the air gap portion remaining between the outer diameter punching hole of the rotor iron core and the inner diameter of the stator iron core is half punched within the range of the plate thickness, and this half punching is performed. A technique for punching the air gap portion as scrap is described. According to the technique described in Patent Document 2, even a small air gap amount can be surely punched and removed as ring-shaped scrap, and a desired air gap portion can be formed.

  Patent Document 3 describes a technique for removing a work-hardened portion formed on each outer peripheral edge of a tooth when a core material of an armature core is formed by punching a thin plate material. According to the technique described in Patent Document 3, the work hardening portion formed on the outer peripheral edge portion of the teeth is removed, and an armature core having excellent magnetic properties is formed by reducing iron loss, so that efficient electric driving is achieved. A motor can be provided.

  There is also known a stator core which is also called a split stator structure formed by arranging a plurality of stator pieces in an arc shape. In the split stator structure, the copper wire can be wound around each of the stator pieces before the stator pieces are arranged and the stator core is formed, so the density of the copper wires to be wound is increased to suppress the current flowing through the copper wires. By doing so, copper loss can be reduced.

  Various techniques for improving the characteristics of the split stator structure are known. For example, Patent Document 4 discloses a value exceeding the minimum value among the values at which the circumferential end surfaces of the yoke portions of the stator pieces facing each other in the circumferential direction all come into contact with each other. The technology to set is described. According to the technique described in Patent Literature 4, since the variation in the width of the gap between the adjacent stator pieces can be reduced, the cogging torque can be reduced.

  Patent Document 5 discloses that the Vickers hardness of the side surface in the circumferential direction of the yoke portion in the tooth portion is lower than the Vickers hardness of the other side surface of the stator piece, and the ratio of the shear surface on the circumferential side surface in the yoke portion is A technique for making the ratio larger than the ratio of the shear surface on the side surface of the part is described. According to the technique described in Patent Document 5, since the Vickers hardness of the side surface of the tooth portion is lower than the Vickers hardness of the side surface of the yoke portion, it is possible to efficiently reduce the iron loss when driving the motor. it can. Further, according to the technique described in Patent Document 5, since the ratio of the shear surface on the side surface in the circumferential direction in the yoke portion is made larger than the ratio of the shear surface on the side surface, the stator core is assembled in an annular shape to manufacture the stator core. Sometimes, the stator core can be assembled with high accuracy.

Japanese Patent No. 5598062 JP 2004-34143 A JP 2007-252092 A Japanese Patent No. 4062943 Japanese Unexamined Patent Publication No. 2011-109834

  With the techniques described in Patent Documents 4 and 5, cogging torque can be suppressed in the divided stator structure, and iron loss can be efficiently reduced. However, as the need for power saving increases, in the divided stator structure, further reduction of iron loss is required without reducing the yield.

  Then, an object of this invention is to provide the technique which can further reduce an iron loss, without reducing a yield in a division | segmentation stator structure.

The gist of the present invention that solves such problems is the following stator core and motor.
(1) a first yoke surface;
A second yoke surface opposite the first yoke surface;
A yoke outer wall extending from one side of the first yoke surface to one side of the second yoke surface;
A yoke inner wall extending from one side of the first yoke surface to one side of the second yoke surface so as to face the yoke outer wall,
A yoke portion having a contact surface extending from the yoke outer wall portion toward the yoke inner wall portion in a direction orthogonal to the first yoke surface and the second yoke surface;
A plurality of stator pieces each having a tooth portion extending in a direction opposite to the yoke outer wall portion from the yoke inner wall portion and arranged such that the contact surfaces are in contact with each other;
The ratio of the height of the contact surface to the height of the yoke side wall is 90% or more,
A stator core characterized in that the contact surface has a Vickers hardness of more than 1 and 1.9 times less than a Vickers hardness of a magnetic steel sheet as a material of a plurality of stator pieces.
(2) The teeth portion includes a first teeth surface, a second teeth surface opposite to the first teeth surface, and a direction from the first teeth surface to the second teeth surface in a direction perpendicular to the first teeth surface and the second teeth surface. A teeth side surface portion having a shaving surface extending toward the
The stator core according to (1), wherein the Vickers hardness of the shaving surface is lower than the Vickers hardness of the contact surface.
(3) The stator core according to (1) or (2), wherein a maximum value of a separation distance between opposing yoke side walls is 3 μm or less.
(4) The stator core according to any one of (1) to (3), wherein the compressive stress in the circumferential direction of the yoke portion is 2 MPa or more and 20 MPa or less.
(5) having a stator having a stator core and a rotor;
The stator core
A first yoke surface;
A second yoke surface opposite the first yoke surface;
A yoke outer wall extending from one side of the first yoke surface to one side of the second yoke surface;
A yoke inner wall extending from one side of the first yoke surface to one side of the second yoke surface so as to face the yoke outer wall,
A yoke portion having a contact surface extending from the yoke outer wall portion toward the yoke inner wall portion in a direction orthogonal to the first yoke surface and the second yoke surface;
A plurality of stator pieces each having a tooth portion extending in a direction opposite to the yoke outer wall portion from the yoke inner wall portion and arranged such that the contact surfaces are in contact with each other;
The ratio of the height of the contact surface to the height of the yoke side wall is 90% or more,
A motor characterized in that the Vickers hardness of the contact surface is more than 1 times and 1.9 times or less of the Vickers hardness of the magnetic steel sheet which is a material of the plurality of stator pieces.

  In the present invention, in the split stator structure, the iron loss can be further reduced without reducing the yield.

It is a top view of a motor which has a stator core concerning a 1st embodiment. (A) is a perspective view of the stator piece shown in FIG. 1, (b) is a partial side view of the stator piece shown in FIG. It is a figure which shows the state which the adjacent stator piece contacts in the stator core shown in FIG. It is a flowchart which shows the manufacturing process of the stator shown in FIG. (A) is a plan view of the punched piece formed by the process of S101, (b) is a partially enlarged view of the punched piece formed by the process of S101, and (c) is formed by the process of S102. It is the elements on larger scale of a stator piece. (A) is a figure which shows the state which has arrange | positioned the stator piece which concerns on a 1st comparative example so that the protrusion direction of a crack may become the same direction, (b) is the protrusion direction of a fog of the stator piece which concerns on a 1st comparative example. (C) is a figure which shows the state which has arrange | positioned the stator piece which concerns on a 2nd comparative example so that the protrusion direction of a crack may become the same direction, 6 (d) is a view showing a state in which the stator pieces according to the second comparative example are arranged such that the protrusion direction of the burrs is opposite, and FIG. 6 (e) is a drawing of the stator pieces according to the third comparative example being the protrusions of the burrs. (F) is a diagram showing a state in which the stator piece according to the third comparative example is arranged so that the protrusion direction of the burrs is opposite, (G) is the same direction as the protrusion direction of the stator piece according to the first embodiment. Is a diagram showing an arrangement state so is a diagram showing a (h) a state arranged such that the projection direction of the burr stator piece according to the first embodiment becomes opposite direction. It is a top view of a motor which has a stator core concerning a 2nd embodiment. (A) is a perspective view of the stator piece shown in FIG. 7, and (b) is a partial side view of the stator piece shown in FIG. It is a flowchart which shows the manufacturing process of the stator shown in FIG. (A) is a plan view of the punched piece formed by the process of S202, (b) is a partially enlarged view of the punched piece formed by the process of S202, and (c) is formed by the process of S203. It is the elements on larger scale of a stator piece. It is a partial top view of the motor used in an Example. It is a figure for demonstrating the measurement of the Vickers hardness of an electromagnetic steel plate.

  Hereinafter, a stator core and a motor according to the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments.

(Outline of stator core according to the embodiment)
The inventors of the present invention have made various experiments and studies for suppressing an increase in iron loss due to non-uniform magnetic flux inside the yoke of the stator core in the split stator structure. In order to solve the above problems, the inventors of the present invention form a contact surface orthogonal to the front surface and the back surface of the side wall portion of the yoke portion in the divided stator structure, thereby forming the side wall portion of the yoke portion of the adjacent stator piece. It has been found that the contact area ratio is improved. The inventors of the present invention improve the contact area ratio of the side wall portion of the yoke portion of the stator piece forming the stator core according to the embodiment, thereby uniformizing the magnetic flux inside the yoke and reducing the iron loss of the motor. I found out. Furthermore, the inventors of the present invention have found that a contact surface orthogonal to the front surface and the back surface is formed by shaving, cutting, or the like.

  More specifically, the inventors of the present invention have found that the ratio of the height of the contact surface to the height of the side wall portion of the yoke portion is 90% or more. Usually, when a steel sheet is punched using a punch and a die, a sag, a sheared surface, a fracture surface, and a burr are formed in order from the moving direction of the punch on the side wall portion of the punched member punched by the punch. In the split stator structure, when the stator pieces punched out by punching are arranged in an annular shape, the shear surfaces protrude most at the side wall of the yoke portion, so that only the shear surfaces contact each other, and the sag, fracture surface and burrs are in contact Without gaps, there will be gaps between sagging, fractured surfaces and burrs. Since the permeability of the gap is lower than the permeability of the magnetic steel sheet, the magnetic flux passing between the adjacent stator pieces is concentrated on the contacting shearing surface. Since the magnetic flux concentrated on the shear surface passes through the position corresponding to the shear surface even inside the yoke away from the side wall of the yoke portion, the magnetic flux density may be uneven in the thickness direction inside the yoke. . When the magnetic flux density becomes non-uniform, a portion where the magnetic flux density becomes unnecessarily high occurs. Since the iron loss increases in proportion to the square of the magnetic flux density, a portion where the magnetic flux density becomes unnecessarily high is generated, so that the iron loss of the motor increases as a whole. In the stator core according to the embodiment, by forming a contact surface in which the ratio of the height of the yoke portion to the height of the side wall portion is 90% or more, the magnetic flux density inside the yoke becomes uniform and the iron loss of the motor is reduced. can do.

(Configuration and function of stator core according to the first embodiment)
FIG. 1 is a plan view of a motor having a stator core according to the first embodiment. In FIG. 1, the direction indicated by arrow A is the circumferential direction, the direction indicated by arrow B is the radial direction, and the direction indicated by dot C is the rotational axis direction.

  The motor 100 includes a housing 101, a rotor 102 also called a rotor, and a stator 103 also called a stator. The casing 101 is formed of a metal such as aluminum having a cylindrical shape, and houses the rotor 102 and the stator 103.

  The rotor 102 includes a shaft 121, a rotor core 122, and a plurality of permanent magnets 123. The shaft 121 is disposed coaxially with the central axis of the cylindrical casing 101 and is rotatably supported via a bearing (not shown). The rotor core 122 is disposed on the outer periphery of the shaft 121 and is fixed coaxially to the shaft 121 so as to rotate integrally with the shaft 121. The plurality of permanent magnets 123 are arranged in the circumferential direction of the motor 100 with a phase shifted by the same angle. Each of the plurality of permanent magnets 123 is disposed so as to penetrate the interior of the rotor core 122 in the direction of the rotation axis.

  The stator 103 includes a fastening ring 131 and a stator core 132. The fastening ring 131 is arranged coaxially with respect to the housing 101. The stator core 132 is formed by a plurality of stator pieces 1 arranged in a circular arc shape and superimposed, and is fixed to the fastening ring 131 coaxially.

  FIG. 2A is a perspective view of the stator piece 1, and FIG. 2B is a partial side view of the stator piece 1. In FIG. 2A, the direction indicated by arrow A is the circumferential direction, the direction indicated by arrow B is the radial direction, and the direction indicated by arrow C is the rotational axis direction.

  Stator piece 1 is formed of an electromagnetic steel plate, and includes yoke portion 10 and teeth portion 20 around which a copper wire is wound. The yoke portion 10 includes a first yoke surface 11, a second yoke surface 12, a yoke outer wall portion 13, a yoke inner wall portion 14, a first yoke side wall portion 15, and a second yoke side wall portion 16. The teeth portion includes a first teeth surface 21, a second teeth surface 22, a teeth inner wall portion 23, a first teeth sidewall portion 24, and a second teeth sidewall portion 25.

  The first yoke surface 11 is the surface of the yoke portion 10, and the second yoke surface 12 is the back surface of the yoke portion 10 opposite to the first yoke surface 11, and each has a substantially rectangular shape. The yoke outer wall portion 13 is a surface extending from one side outside the first yoke surface 11 in the radial direction to one side outside the second yoke surface 12 in the radial direction. The yoke inner wall portion 14 is a surface extending from one side in the radial direction of the first yoke surface 11 to one side in the radial direction of the second yoke surface 12 so as to face the yoke outer wall portion 13.

  The first yoke side wall portion 15 is a wall portion extending from the yoke outer wall portion 13 toward the yoke inner wall portion 14, and includes a sag 151, a contact surface 152, a fracture surface 153, and a burr 154. The mechanism by which the sagging 151, the fracture surface 153, and the burrs 154 are formed is well known, and thus detailed description thereof is omitted here. Further, the configuration and function of the components of the second yoke side wall portion 16 are the same as the configuration and function of the first yoke side wall portion 15, so detailed description thereof will be omitted here. The contact surface 152 extends in a direction perpendicular to the first yoke surface 11 and the second yoke surface 12, and is formed in the punching step S101 and the shaving step S102 performed thereafter. The contact surface 152 contacts the contact surface 152 of the adjacent stator piece 1 in the stator core 132. The ratio of the height of the contact surface 152 to the height of the side wall is 90% or more.

  FIG. 3 is a diagram illustrating a state in which adjacent stator pieces 1 are in contact with each other in the stator core 132.

  Adjacent stator pieces 1 are arranged such that their contact surfaces 152 are in contact with each other. When the contact surfaces 152 of the adjacent stator pieces 1 come into contact with each other, the sag 151, the fracture surface 153, and the burr 154 of the adjacent stator pieces 1 are spaced apart.

  The separation distance between the stator pieces 1 that is the distance between the burrs 154 is preferably 3 μm or less, and more preferably 2 μm or less. When the separation distance between the stator pieces 1 exceeds 3 μm, the magnetic flux passing between the adjacent stator pieces 1 concentrates on the contact surface 152, and the increase in iron loss of the stator core 132 increases. By setting the separation distance between the stator pieces 1 to 3 μm or less, an increase in iron loss of the stator core 132 is suppressed. Moreover, the increase in the iron loss of the stator core 132 is further suppressed by setting the separation distance between the stator pieces 1 to 2 μm or less. Note that the separation distance is 0 μm when there is no fracture surface 153 and burrs 154 and the ratio of the height of the contact surface to the height of the yoke side wall is 100%.

  The 1st teeth surface 21 is the surface of teeth part 20, and the 2nd teeth surface 22 is the back of teeth part 20 opposite to the 1st teeth surface 21, and each is formed in the shape of a rectangle. The teeth inner wall portion 23 is a surface that extends from one side in the radial direction of the first tooth surface 21 to one side in the radial direction of the second tooth surface 22 so as to face the yoke outer wall portion 13. Each of the first tooth side wall part 24 and the second tooth side wall part 25 is a wall part extending from the yoke inner wall part 14 toward the tooth inner wall part 23.

(Manufacturing process of stator according to first embodiment)
FIG. 4 is a flowchart showing manufacturing steps of the stator according to the first embodiment.

  First, the unillustrated press working apparatus forms a punched piece by punching the electromagnetic steel sheet (S101). Next, the unillustrated press working apparatus forms the stator piece 1 by performing the shaving process on the side wall portion of the yoke portion of the punched piece formed in the process of S101 (S102).

  5A is a plan view of the punched piece formed by the process of S101, FIG. 5B is a partially enlarged view of the punched piece formed by the process of S101, and FIG. 5C is S102. It is the elements on larger scale of the stator piece 1 formed by the process of.

  The punched piece 110 has a yoke part 111 and a tooth part 112. A press working apparatus (not shown) forms the stator piece 1 by shaving the side wall of the yoke 111 shown by arrows A and B, respectively. Shaving processing by a press processing apparatus (not shown) is executed by a single shaving process.

Shaving width L _C being cut by a shaving process shown in S102 is preferably less than 5% to 40% of the thickness L _T of the punching piece 110, 25% more than 35% of the thickness L _T of the punched piece 110 More preferably, it is as follows. The shaving width L _C, by 5% or more than 40% of the thickness L _T of the punching piece 110, the distance between the stator pieces 1 can be 3μm or less. The shaving width L _C, by 25% or more than 35% of the thickness L _T of the punching piece 110, the distance between the stator pieces 1 can be 2μm or less.

  The Vickers hardness of the contact surface 152 of the first yoke side wall portion 15 and the contact surface (not shown) of the second yoke side wall portion 16 of the stator piece 1 formed by the processing of S102 is a magnetic steel sheet that is a material of the plurality of stator pieces 1 The Vickers hardness is preferably more than 1 time and 1.9 times or less. When shaving is performed by a single shaving process, the Vickers hardness of the contact surface 152 of the first yoke side wall 15 and the contact surface (not shown) of the second yoke side wall 16 is an electromagnetic wave that is a material of a plurality of stator pieces. More than 1 time and less than 1.9 times the Vickers hardness of the steel sheet.

  The Vickers hardness of the electrical steel sheet is measured based on, for example, JIS Z 2244: 2009. The electrical steel sheet used for the measurement is cut so as to include a punched end face, and the cut face is smooth and free from irregularities, oxide films (scales) and foreign matters, and is particularly free from a lubricant. When finishing the cut surface, the surface hardness is not changed as much as possible due to overheating or cold working. The hardness measurement is performed at a certain distance from the vicinity of the punched end face. It is necessary to determine the measurement load according to the material hardness, the interval to be measured, and the smaller thickness. For example, when the hardness measurement is performed at 50 μm intervals with 50A350 having a plate thickness of 0.5 mm, a measurement load of about 25 gf is suitable. When the hardness measurement is performed at an interval narrower than 50 μm, it is necessary to devise such as shifting the hitting point obliquely as shown in FIG. 12 so as not to affect the adjacent indentation.

  When a steel plate is punched, high processing strain is introduced in the vicinity of the punched end face, and the Vickers hardness in the vicinity of the end face is increased. Hardness increase, the distance from the punched end surface where the hardness increases varies depending on the thickness of the steel plate, the mechanical strength of the steel plate, and the clearance between the die and the punch. The hardness continuously changes toward the inside of the steel plate. The region in which the hardness increases is from the vicinity of the punched end face pole to the plate thickness equivalent to about 1/2 the plate thickness. In the region where the processing strain is introduced, the magnetic characteristics deteriorate and the iron loss increases. In Patent Documents 1, 2, and 5, motor iron loss is reduced by removing a region where machining distortion is introduced by shaving. For this purpose, the increase in the Vickers hardness in the vicinity of the punched end face after the shaving process is almost doubled. On the other hand, in the present invention, it is not always necessary to remove the entire region where the processing strain is introduced, and even if the processing strain remains, increasing the contact surface makes the magnetic flux density uniform and reduces the motor iron loss. For this purpose, it is necessary that the Vickers hardness of the contact surface be more than 1 time and not more than 1.9 times the Vickers hardness of the magnetic steel sheet that is the material of the plurality of stator pieces. If it is set to 1 time, the processing strain introduced portion can be removed and the motor iron loss can be reduced, but the width to be removed by shaving is increased, the yield is lowered, and the die life tends to be reduced. The reduction of the motor iron loss, which is the object of the present invention, can be achieved by increasing the contact surface if it is more than 1 time but up to 1.9 times. If it exceeds 1.9 times, the effect of increasing the motor iron loss due to the introduction of processing strain becomes larger than the effect of reducing the motor iron loss due to the increase in the contact surface. The Vickers hardness is defined as more than 1 time and 1.9 times or less. From the viewpoint of improving yield, the Vickers hardness of the contact surface is preferably 1.02 times or more, more preferably 1.04 times or more of the Vickers hardness of the electromagnetic steel sheet that is the material of the plurality of stator pieces. From the viewpoint of removal of processing strain, the Vickers hardness of the contact surface is desirably 1.8 times or less, more desirably 1.7 times or less of the Vickers hardness of the electrical steel sheet that is the material of the plurality of stator pieces.

  Note that the ratio of the height of the contact surface to the height of the yoke side wall can be controlled as follows.

  In other words, the relationship between the shaving removal width and the contact surface height when the punched steel sheet is shaved by changing the removal width is determined in advance for each punching condition (die and punch clearance, etc.). Based on this relationship, the height of the contact surface can be controlled.

  The Vickers hardness of the contact surface can also be controlled based on the relationship between the shaving removal width and the hardness obtained for each punching condition.

  From these, the ratio of the contact surface to the height of the yoke side wall can be controlled independently of the hardness of the contact surface by appropriately selecting the punching conditions and the shaving removal width.

  Next, the stator assembly device (not shown) stacks the stator pieces 1 formed by the process of S102 (S103). Next, the stator assembly device (not shown) assembles the stator pieces 1 stacked in the process of S103 into an arc shape (S104). Then, the stator assembly device (not shown) fixes the stator piece 1 assembled in the process of S104 by performing shrink fitting on the fastening ring 131 (S105).

  The shrink fitting process shown in S105 is performed so that the compressive stress in the circumferential direction of the yoke portion 10 of the stator core 132 is 2 MPa or more and 20 MPa or less. When the compressive stress in the circumferential direction of the yoke portion 10 is less than 2 MPa, the gap between the contact surfaces 152 of the adjacent stator pieces 1 is likely to be large and non-uniform, resulting in non-uniform magnetic flux density. Iron loss may increase. In general, when the compressive stress in the circumferential direction of the yoke portion 10 increases, the iron loss of the motor 100 increases. If the compressive stress in the circumferential direction of the yoke portion 10 exceeds 20 MPa, an increase in iron loss of the motor 100 cannot be ignored. Therefore, the compressive stress in the circumferential direction of the yoke portion 10 is set to 20 MPa or less. The compressive stress in the circumferential direction of the yoke portion 10 is more preferably 5 MPa or more and 15 MPa or less. By setting the compressive stress in the circumferential direction of the yoke portion 10 to 15 MPa or less, an increase in iron loss due to the compressive stress can be suppressed. Moreover, by setting it as 5 MPa or more, the gap between the contact surfaces 152 of the adjacent stator pieces 1 can be made smaller and more uniform, magnetic flux density non-uniformity can be suppressed, and an increase in iron loss of the motor 100 can be suppressed. it can.

  The compressive stress in the circumferential direction of the yoke portion 10 is measured by disposing a strain gauge on the first yoke surface 11. The strain gauge is arranged so as to measure a compressive stress in a direction orthogonal to the first yoke side wall 15. For the strain gauge, use product number KFGS-10-120-D16-11 manufactured by Kyowa Denki Co., Ltd. or equivalent.

(Operational effect of the stator core according to the first embodiment)
FIG. 6A is a view showing a state in which the stator pieces according to the first comparative example are arranged so that the protrusion directions of the burrs are the same direction, and FIG. 6B is a view showing the stator pieces according to the first comparative example. It is a figure which shows the state arrange | positioned so that the protrusion direction of a fly may become a reverse direction. FIG. 6C is a view showing a state in which the stator pieces according to the second comparative example are arranged so that the protrusion directions of the burrs are the same, and FIG. 6D is a view showing the stator pieces according to the second comparative example. It is a figure which shows the state arrange | positioned so that the protrusion direction of a fly may become a reverse direction. FIG. 6 (e) is a view showing a state in which the stator pieces according to the third comparative example are arranged so that the protrusion directions of the burrs are the same direction, and FIG. 6 (f) shows the stator pieces according to the third comparative example. It is a figure which shows the state arrange | positioned so that the protrusion direction of a fly may become a reverse direction. FIG. 6G is a view showing a state in which the stator pieces according to the first embodiment are arranged so that the protrusion directions of the burrs are in the same direction, and FIG. It is a figure which shows the state arrange | positioned so that the protrusion direction of a fly may become a reverse direction.

  In the stator piece 901 according to the first comparative example, the ratio of the height to the height of the side wall portion of the yoke portion is 25%, and in the stator piece 902 according to the second comparative example, the height relative to the height of the side wall portion of the yoke portion. The height ratio is 45%. Further, in the stator piece 903 according to the third comparative example, the ratio of the height to the height of the side wall portion of the yoke portion is 70%. In the stator piece 1 according to the first embodiment, the height of the side wall portion of the yoke portion is high. The ratio of height to height is 90%.

  In the state in which the stator pieces 901 to 903 according to the first comparative example to the third comparative example are arranged so that the protrusion direction of the burr is the same direction, the shear plane comes into contact with the adjacent stator pieces 901 to 903, Fracture surfaces and burrs do not touch. The stator pieces 901 to 903 according to the first comparative example to the third comparative example are in contact with each other only in the shear plane, and the magnetic flux is adjacent through the 25%, 45% and 70% regions of the side wall portion of the yoke portion. Since it passes between the pieces, the magnetic flux density may be non-uniform.

  In the state where the stator pieces 901 according to the first comparative example are arranged so that the protrusion directions of the burrs are opposite, none of the sagging, the shearing surface, the fracture surface, and the burrs are in contact with the adjacent stator pieces 901. When the stator pieces 902 to 903 according to the second comparative example to the third comparative example are arranged so that the protrusion direction of the burrs is opposite, only a part of the shearing surface contacts, The part, fracture surface and burrs do not touch. In the stator piece 901 according to the first comparative example, none of the sag, the sheared surface, the fracture surface, or the burr is in contact, and in the stator pieces 902 to 903 according to the second comparative example to the third comparative example, only a part of the sheared surface is obtained. , The magnetic flux density inside the stator pieces 901 to 903 becomes further non-uniform.

  On the other hand, in the stator core according to the first embodiment, since the ratio of the height of the contact surface to the height of the side wall portion of the contact surface is 90% or more, the stator piece 1 is arranged so that the protrusion direction of the burrs is the same direction. In this state, the area where the adjacent stator pieces 1 are in contact with each other is increased. In the stator core according to the first embodiment, since the area where the adjacent stator pieces 1 are in contact with each other is increased, the magnetic flux density inside the yoke becomes uniform, and the iron loss of the motor can be reduced.

  Further, in the stator core according to the first embodiment, even when the stator pieces 1 are arranged so that the protrusion direction of the burrs is opposite, the area where the adjacent stator pieces 1 come into contact with each other becomes large. In the stator core according to the first embodiment, since the area where the adjacent stator pieces 1 are in contact with each other is increased, the magnetic flux density inside the yoke becomes uniform, and the iron loss of the motor can be reduced.

(Configuration and Function of Stator Core According to Second Embodiment)
FIG. 7 is a plan view of a motor having a stator core according to the second embodiment. In FIG. 7, the direction indicated by the arrow A is the circumferential direction, the direction indicated by the arrow B is the radial direction, and the direction indicated by the dot C is the rotation axis direction.

  The motor 200 is different from the motor 100 in having a stator 203 (a stator according to a second embodiment described below) instead of the stator 103. The stator 203 is different from the stator 103 in having a stator core 232 instead of the stator core 132. The stator core 232 is different from the stator core 132 in that the stator piece 2 has the stator piece 2 instead of the stator piece 1. Since the configuration and functions of the components of the motor 200 other than the stator piece 2 are the same as the configurations and functions of the components of the motor 100 denoted by the same reference numerals, detailed description thereof is omitted here.

  FIG. 8A is a perspective view of the stator piece 2, and FIG. 8B is a partial side view of the stator piece 2. In FIG. 8A, the direction indicated by arrow A is the circumferential direction, the direction indicated by arrow B is the radial direction, and the direction indicated by arrow C is the rotational axis direction.

  The stator piece 2 is different from the stator piece 1 in that it has a tooth portion 30 instead of the tooth portion 20. The tooth part 30 is different from the tooth part 20 in that the first tooth side wall part 34 and the second tooth side wall part 35 are provided instead of the first tooth side wall part 24 and the second tooth side wall part 25. The configuration and function of the constituent elements of the stator piece 2 other than the first tooth side wall portion 34 and the second tooth side wall portion 35 are the same as the configuration and function of the constituent elements of the stator piece 1 denoted by the same reference numerals. The detailed explanation is omitted. Moreover, since the structure and function of the component of the 2nd teeth side wall part 35 are the same as the structure and function of the 1st teeth side wall part 34, detailed description is abbreviate | omitted here.

  The first tooth side wall 34 includes a sag 341, a shaving surface 342, a fracture surface 343, and a burr 344. Since the mechanism by which the sagging 341, the fracture surface 343, and the burrs 344 are formed is well known, detailed description thereof is omitted here.

  After the punching process, the shaving surface 342 is subjected to a shaving process that removes a region corresponding to a ratio of 5% to 25% with respect to the height of the first tooth side wall part 34 twice or more. It is formed to have a height of 40% to 60% of the height.

  A new plastic strain is introduced in the vicinity of the shaving surface 342 by forming a shaving surface 342 by shaving each region corresponding to a ratio of 5% to 25% with respect to the height of the first tooth side wall portion 34. The plastic strain due to the punching process can be removed without any problems.

  In the shaving surface 342, since plastic strain due to punching is removed without introducing new plastic strain, the iron loss of the motor 200 can be reduced as described in Patent Document 1. Further, the Vickers hardness of the shaving surface 342 is lower than the Vickers hardness of the contact surface 152 formed by a single shaving process because the shaving is performed so as to remove all distortion during the punching process.

(Manufacturing process of stator according to second embodiment)
FIG. 9 is a flowchart showing manufacturing steps of the stator according to the second embodiment.

  Since the processing of S201 and S202 is the same as the processing of S101 and S102, detailed description thereof is omitted here. Next, the unillustrated press working apparatus forms the stator piece 2 by performing the shaving process on the side wall portion of the tooth portion of the punched piece whose side wall portion of the yoke portion has been subjected to the shaving process in the processing of S202 (S203). In the process of S203, the shaving surface 342 is subjected to a shaving process that removes a region corresponding to a ratio of 5% to 25% with respect to the height of the first tooth side wall portion 34 twice or more, so that the height of the first tooth side wall portion 34 is increased. It is formed so as to have a height of 40% to 60%. Also in the 2nd teeth side wall part 35, the shaving process which deletes the area | region corresponded to 5%-25% of the ratio with respect to the height of the 2nd teeth side wall part 35 is performed twice or more, and the height of the 2nd teeth side wall part 35 A shaving surface having a height of 40% to 60% is formed.

  10A is a plan view of the punched piece formed by the process of S202, FIG. 10B is a partially enlarged view of the punched piece formed by the process of S202, and FIG. 10C is S203. It is the elements on larger scale of the stator piece 2 formed by the process of.

  The punched piece 210 has a yoke portion 211 and a teeth portion 212. A press working apparatus (not shown) forms the stator piece 1 by performing shaving on the side wall portion of the tooth portion 212 indicated by arrows A and B, respectively. Shaving processing by a press processing apparatus (not shown) is executed by shaving processing over a plurality of times.

Shaving width L _C being cut by a shaving process shown in step S203, is preferably less than 5% to 40% of the thickness L _T punching piece 210. The shaving width L _C, by 5% or more than 40% of the thickness L _T punching piece 210, without newly to introduce plastic strain in the vicinity of an end face of shaving unit by shaving process, punching is facilities Plastic strain can be removed from the vicinity of the end face.

  Since the process of S204-S206 is the same as the process of S103-S105, detailed description is abbreviate | omitted here.

(Modification of stator core according to the embodiment)
In the stator cores 132 and 232, the contact surface 152 is formed by shaving, but in the stator core according to the embodiment, the contact surface formed on the side wall portion of the yoke portion may be formed by cutting.

  FIG. 11 is a partial plan view of a motor used in the embodiment.

  The motor 300 is an IPM motor manufactured based on the Institute of Electrical Engineers D model using a non-oriented electrical steel sheet 50A350. The outer diameter of the stator core 332 is 112 mm, the outer diameter of the rotor 302 is 54 mm, and the stacked height of the stator pieces 3 is 100 mm. The number of slots is 24 slots. The stator core 332 has a yoke portion divided into 24 in the circumferential direction. The outer diameter of the rotor 302 is 54 mmφ, the inner diameter of the stator core 332 is 55 mmφ, and the gap between the rotor 302 and the stator core 332 is 0.5 mm. The outer diameter of the stator core 332 is 112 mmφ (= 54 mm + 0.5 mm × 2 + 28.5 mm × 2).

  The stator piece according to the first example was formed by shaving so that the ratio of the height of the contact surface of the side wall of the yoke portion was 90% of the height of the side wall after punching with a die and a punch. . The shaving amount in the first embodiment is 0.1 mm on one side. In the first embodiment, the stator was formed by arranging and stacking 24 stator pieces in an arc shape and then shrink fitting so that the compressive stress in the circumferential direction of the yoke portion was 10 MPa. The stator core has 24 slots, the number of windings per phase of the copper wire wound around the teeth portion of the stator core is 35 turns, and the magnetic flux density Br of the rotor magnet is 1.25T. The ratio of the electrical steel sheet, which is a material having a Vickers hardness (load 25 gf) measured on the contact surface, to the Vickers hardness was 1.35 times, and the separation distance was 2 μm.

  In the stator piece according to the second embodiment, after punching with a die and a punch, the side surface of the yoke portion is adjusted so that the ratio of the contact surface height of the side wall portion of the yoke portion is 90% of the height of the side wall portion. It was polished and smoothed by a grinder. The grinder polishing amount in the second embodiment is 0.1 mm on one side. In the second embodiment, as in the first embodiment, after the 24 stator pieces are arranged in an arc shape and stacked, the stator core is shrink-fitted so that the compressive stress in the circumferential direction of the yoke portion is 10 MPa. Formed with. The number of slots, the number of windings per phase of the copper wire wound around the teeth portion of the stator core, and the magnetic flux density Br of the rotor magnet are the same as in the first embodiment. The ratio of the electrical steel sheet, which is a material having a Vickers hardness (load 25 gf) measured on the contact surface, to the Vickers hardness was 1.35 times, and the separation distance was 2 μm.

  The stator piece according to the first comparative example was formed by punching with a die and a punch so that the yoke width was the same as in the first and second examples. In the first comparative example, the stator core was formed by arranging and stacking 24 stator pieces in an arc shape and then shrink fitting so that the compressive stress in the circumferential direction of the yoke portion was 10 MPa. The number of slots, the number of windings per phase of the copper wire wound around the teeth portion of the stator core, and the magnetic flux density Br of the rotor magnet are the same as in the first embodiment. The ratio of the Vickers hardness (load 25 gf) measured on the contact surface to the Vickers hardness of the magnetic steel sheet is double, the separation distance is 2 μm, and the height ratio of the contact surface of the side wall portion of the yoke portion is the height of the side wall portion. Of 90%.

  In the first example, the second example, and the first comparative example, the iron loss of the motor was measured when a winding current having a peak value of 3A was passed at a phase angle of 30 degrees and the motor was driven at a rotational speed of 1500 RPM. The iron loss of the motor was calculated by subtracting the mechanical loss measured in advance and the copper loss calculated from the winding current and the resistance value of the winding from the total loss that is the difference between the input power and the output power.

  Table 1 shows the iron loss per unit weight (unit: W) of the motors according to the first example, the second example and the first comparative example calculated by dividing the calculated copper loss by the weight of each motor. / Kg). Table 2 also shows iron loss per unit weight (unit: W / kg) measured with the toroidal winding applied to the yoke portion of the stator piece before winding, and the yoke portion regarded as a ring.

  In both Table 1 and Table 2, the iron loss per unit weight of the first example and the second example is smaller than the iron loss per unit weight of the first comparative example. In the first and second embodiments, the iron loss is reduced by increasing the contact surface of the yoke portion.

  In the same manner as in Example 1, the iron loss per unit weight (unit: W / kg) of an IPM motor manufactured using the non-oriented electrical steel sheet 50A350 and based on the Institute of Electrical Engineers of Japan D model was calculated. Each of the third example, the fourth example, and the second comparative example is the same as the first example, the second example, and the first comparative example, except for the compressive stress in the circumferential direction of the yoke portion in the shrink fitting process. Formed. Each of the third example, the fourth example, and the second comparative example was formed by shrink fitting so that the compressive stress in the circumferential direction of the yoke portion was 50 MPa.

  In the third example, the fourth example, and the second comparative example, the iron loss of the motor was measured when a winding current having a peak value of 3A was passed at a phase angle of 30 degrees and the motor was driven at a rotational speed of 1500 RPM. The iron loss of the motor was calculated in the same manner as in Example 1.

  Table 3 shows the iron loss per unit weight (unit: W / kg) of the third example, the fourth example and the second comparative example calculated by dividing the calculated copper loss by the weight of each motor. Indicates. Table 4 also shows iron loss per unit weight (unit: W / kg) measured with the toroidal winding applied to the yoke portion of the stator piece 3 before winding, and the yoke portion regarded as a ring. .

  In both Table 3 and Table 4, the iron loss per unit weight of the third example and the fourth example is smaller than the iron loss per unit weight of the second comparative example. In the third and fourth embodiments, the iron loss is reduced by increasing the contact surface of the yoke portion.

  In the same manner as in Example 1, the iron loss per unit weight (unit: W / kg) of an IPM motor manufactured using the non-oriented electrical steel sheet 50A350 and based on the Institute of Electrical Engineers of Japan D model was calculated. Each of the fifth example, the third comparative example, the fourth comparative example, and the fifth comparative example was formed by performing a shaving process after punching with a die and a punch as in the first example. In the fifth embodiment, the shaving process was performed such that the ratio of the height of the contact surface of the side wall portion of the yoke portion was 90% of the height of the side wall portion. In each of the third to fifth comparative examples, the shaving process was performed so that the ratio of the height of the contact surface of the side wall portion of the yoke portion was 25%, 40%, and 70% of the height of the side wall portion. The ratio of the Vickers hardness (load 25 gf) measured on the contact surfaces of the fifth example, the third comparative example, the fourth comparative example, and the fifth comparative example to the Vickers hardness of the magnetic steel sheet is 1.35 times. The separation distance was 2 μm. Each of the fifth example, the third comparative example, the fourth comparative example, and the fifth comparative example was formed by shrink fitting so that the compressive stress in the circumferential direction of the yoke portion was 10 MPa.

  The fifth example was formed in the same manner as the first example. Each of the third comparative example, the fourth comparative example, and the fifth comparative example was formed in the same manner as the first comparative example except for the ratio of the height of the contact surface of the side wall portion of the yoke portion.

  In the fifth embodiment, the third comparative example, the fourth comparative example, and the fifth comparative example, the iron loss of the motor when the winding current having a peak value of 3A is passed at a phase angle of 30 degrees and driven at a rotational speed of 1500 RPM. Was measured. The iron loss of the motor was calculated in the same manner as in Example 1.

  Table 5 shows the iron loss per unit weight (unit) of the fifth example, the third comparative example, the fourth comparative example, and the fifth comparative example calculated by dividing the calculated copper loss by the weight of each motor. : W / kg). Table 6 shows iron loss per unit weight (unit: W / kg) measured by applying toroidal winding to the yoke portion of the stator piece before winding, and regarding the yoke portion as a ring.

  In both Table 5 and Table 6, the iron loss of the fifth embodiment in which the ratio of the contact surface height of the side wall portion of the yoke portion is 90% of the height of the side wall portion is the contact surface of the side wall portion of the yoke portion. The height ratio is much smaller than the third comparative example, the fourth comparative example, and the fifth comparative example, which do not reach 90% of the height of the side wall.

  In the same manner as in Example 1, the iron loss per unit weight (unit: W / kg) of an IPM motor manufactured using the non-oriented electrical steel sheet 50A350 and based on the Institute of Electrical Engineers of Japan D model was calculated. In each of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example, when the punching process is performed, the clearance between the stator pieces is changed by changing the clearance between the die and the punch. The distance was formed to change. In each of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example, the separation distance between the stator pieces is 1 μm, 3 μm, 4 μm, and 5 μm. In each of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example, the ratio of the electrical steel sheet that is the material of the Vickers hardness (load 25 gf) measured on the contact surface to the Vickers hardness is 1.04 times. 1.35 times, 1.55 times and 1.65 times. Moreover, the ratio of the height of the contact surface of the side wall part of the yoke part of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example was 90% of the height of the side wall part. Each of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example was formed by shrink fitting so that the compressive stress in the circumferential direction of the yoke portion was 10 MPa.

  The sixth and seventh embodiments were formed in the same manner as the first embodiment except that the clearance between the die and the punch was changed. Each of the sixth comparative example and the seventh comparative example was formed in the same manner as the first comparative example, except that the clearance between the die and the punch was changed.

  In the sixth embodiment, the seventh embodiment, the sixth comparative example, and the seventh comparative example, the iron loss of the motor when the winding current having a peak value of 3A is caused to flow at a phase angle of 30 degrees and driven at a rotational speed of 1500 RPM. Was measured. The iron loss of the motor was calculated in the same manner as in Example 1.

  Table 7 shows iron losses per unit weight (units) of the sixth example, the seventh example, the sixth comparative example, and the seventh comparative example calculated by dividing the calculated copper loss by the weight of each motor. : W / kg). Table 8 shows the iron loss per unit weight (unit: W / kg) measured with the toroidal winding applied to the yoke portion of the stator piece before winding, and the yoke portion regarded as a ring.

  In both Tables 7 and 8, the iron loss of the seventh example in which the separation distance between the stator pieces is 3 μm is the sixth comparative example in which the separation distance between the stator pieces 3 is 4 μm or more, and the seventh comparison. Much smaller than the example.

  In the same manner as in Example 1, the iron loss per unit weight (unit: W / kg) of an IPM motor manufactured using the non-oriented electrical steel sheet 50A350 and based on the Institute of Electrical Engineers of Japan D model was calculated. The stator pieces according to the eighth example, the ninth example, the tenth example, the eighth comparative example, and the ninth comparative example are stamped with a die and a punch, and then the shaving width is one side of the side wall of the yoke part. Molding was performed by shaving so as to be 50 μm, 100 μm, 150 μm, 175 μm, and 250 μm. In the eighth example, the ninth example, the tenth example, the eleventh example, and the eighth comparative example, the dimensions before shaving were adjusted so that the yoke widths after the shaving were the same. The stator piece according to the ninth comparative example is stamped by a die and a punch so that the yoke width is the same as that of the eighth example, the ninth example, the tenth example, the eleventh example and the eighth comparative example. Was molded by.

  In each of the eighth example, the ninth example, the tenth example, the eleventh example, the eighth comparative example, and the ninth comparative example, the separation distance is 2.5 μm, 2 μm, 1.5 μm, 1 μm, 0 μm and It was 3 μm. Further, the ratio of the height of the contact surface of the side wall portion of the yoke portion of the eighth embodiment, the ninth embodiment, the tenth embodiment, the eleventh embodiment and the eighth comparative example is 90% of the height of the side wall portion. The ratio of the contact surface height of the side wall portion of the yoke portion of the ninth comparative example was 70% of the height of the side wall portion. Each of the eighth example, the ninth example, the tenth example, the eleventh example, the eighth comparative example, and the ninth comparative example is shrink-fitted so that the compressive stress in the circumferential direction of the yoke portion is 10 MPa. Was formed.

  In the eighth example, the ninth example, the tenth example, the eleventh example, the eighth comparative example, and the ninth comparative example, a winding current having a peak value of 3A is passed at a phase angle of 30 degrees, and the rotation speed is 1500 RPM. The iron loss of the motor when driven by a number was measured. The iron loss of the motor was calculated in the same manner as in Example 1.

  Table 9 shows an eighth embodiment, a ninth embodiment, a tenth embodiment, an eleventh embodiment, an eighth comparative example, and a ninth comparison calculated by dividing the calculated iron loss by the weight of each motor. The iron loss per unit weight (unit: W / kg), the ratio of Vickers hardness (load 25 gf) measured on the contact surface to the Vickers hardness of the magnetic steel sheet as a material (unit: times), and the punching yield are shown. Table 10 shows the iron loss per unit weight (unit: W / kg) and the contact surface measured with the toroidal winding applied to the yoke portion of the stator piece before winding, and the yoke portion regarded as a ring. The ratio (unit: times) with respect to the Vickers hardness of the electrical steel sheet which is a material of Vickers hardness (load 25gf) measured by (1) is shown. In Tables 9 and 10, the first stage shows the iron loss per unit weight (unit: W / kg), the second stage shows the Vickers hardness (unit: times), and the third stage shows the punching yield.

  In both Table 9 and Table 10, the ratio of Vickers hardness (load: 25 gf) measured on the contact surface to the Vickers hardness of the magnetic steel sheet as the material (unit: times) is more than 1 time and 1.9 times or less. The iron loss of the examples, the ninth example, the tenth example, the eleventh example and the eighth comparative example has a ratio (unit: multiple) to the Vickers hardness of the electrical steel sheet which is a material having a Vickers hardness (load 25 gf). It is smaller than the ninth comparative example which is more than 9 times. In the eighth comparative example, the iron loss per unit weight was almost the same as that of the tenth and eleventh examples, but the punching yield was greatly deteriorated to 70% or less.

1, 2, 3 Stator piece 10 Yoke part 15 First yoke side wall part 16 Second yoke side wall part 20, 30 Teeth part 24, 34 First tooth side wall part 25, 35 Second tooth side wall part 100, 200, 300 Motor 101 Case 102 Rotor 103, 203, 303 Stator 132, 232, 332 Stator core 151 Sag 152 Contact surface 153 Fracture surface 154

Claims (5)

A first yoke surface;
A second yoke surface opposite the first yoke surface;
A yoke outer wall extending from one side of the first yoke surface to one side of the second yoke surface;
A yoke inner wall portion extending from one side of the first yoke surface to one side of the second yoke surface so as to face the yoke outer wall portion;
A yoke portion having a contact surface extending from the yoke outer wall portion toward the yoke inner wall portion in a direction perpendicular to the first yoke surface and the second yoke surface;
A plurality of stator pieces each having a tooth portion extending in a direction opposite to the yoke outer wall portion from the yoke inner wall portion and disposed so that the contact surfaces are in contact with each other;
The ratio of the height of the contact surface to the height of the yoke side wall is 90% or more,
The stator core according to claim 1, wherein a Vickers hardness of the contact surface is more than 1 times and 1.9 times or less of a Vickers hardness of a magnetic steel sheet as a material of the plurality of stator pieces. The teeth portion includes a first tooth surface, a second tooth surface opposite to the first tooth surface, and the first tooth surface and the second tooth surface perpendicular to the first tooth surface and the second tooth surface. A tooth side surface portion having a shaving surface extending in the direction of
The stator core according to claim 1, wherein a Vickers hardness of the shaving surface is lower than a Vickers hardness of the contact surface.   The stator core according to claim 1 or 2, wherein a maximum value of a separation distance between the opposing yoke side walls is 3 µm or less.   The stator core according to any one of claims 1 to 3, wherein a compressive stress in a circumferential direction of the yoke portion is 2 MPa or more and 20 MPa or less. A stator having a stator core and a rotor;
The stator core is
A first yoke surface;
A second yoke surface opposite the first yoke surface;
A yoke outer wall extending from one side of the first yoke surface to one side of the second yoke surface;
A yoke inner wall portion extending from one side of the first yoke surface to one side of the second yoke surface so as to face the yoke outer wall portion;
A yoke portion having a contact surface extending in a direction perpendicular to the first yoke surface and the second yoke surface from the yoke outer wall portion toward the yoke inner wall portion;
A plurality of stator pieces each having a tooth portion extending in a direction opposite to the yoke outer wall portion from the yoke inner wall portion and disposed so that the contact surfaces are in contact with each other;
The ratio of the height of the contact surface to the height of the yoke side wall is 90% or more,
The motor according to claim 1, wherein a Vickers hardness of the contact surface is more than 1 times and 1.9 times or less of a Vickers hardness of a magnetic steel sheet which is a material of the plurality of stator pieces.

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