Patent Grant
11888347
The present application is based on PCT filing PCT/JP2019/040974, filed Oct. 17, 2019, which claims priority to Japanese Patent Application No. 2018-228584, filed on Dec. 5, 2018, the entire contents of each are incorporated herein by reference.
The present disclosure relates to a core, a stator, and a rotary electric machine.
PTL 1 discloses an axial-gap rotary electric machine including a rotor and a stator arranged to face each other in an axial direction. This type of rotary electric machine includes a stator including a core and coils. The core includes a circular annular yoke portion and a plurality of tooth portions that project from the yoke portion in the axial direction. The coils are provided around respective ones of the tooth portions. According to PTL 1, the core is divided into a plurality of core pieces in the circumferential direction, and each core piece is formed of a dust core including a yoke portion and tooth portions that are formed integrally with the yoke portion.
A core according to the present disclosure is for use in an axial-gap rotary electric machine. The core is annular and includes a plurality of core pieces into which the core is divided in a circumferential direction. Each core piece includes a yoke portion and a tooth portion that is formed integrally with the yoke portion and that projects from the yoke portion in an axial direction. Each yoke portion includes a plurality of protrusions provided on one side surface that is connected to the yoke portion of an adjacent one of the core pieces, and a plurality of recesses provided on other side surface that is connected to the yoke portion of another adjacent one of the core pieces, the recesses corresponding to the protrusions. An interval between the protrusions is 80% or less of a length of the one side surface of the yoke portion, the length being a direct distance between inner and outer peripheries of the yoke portion.
A stator according to the present disclosure is a stator for an axial-gap rotary electric machine, and includes the core according to the present disclosure and a coil disposed on each of the tooth portions of the core pieces that constitute the core.
A rotary electric machine according to the present disclosure includes a rotor and a stator. The rotary electric machine is an axial-gap rotary electric machine in which the rotor and the stator are arranged to face each other in an axial direction. The stator is the stator according to the present disclosure.
To facilitate production of the axial-gap rotary electric machine, it is desirable to facilitate assembly of the core.
When the core is formed of a plurality of core pieces, the core pieces need to be assembled into an annular shape such that side surfaces of yoke portions of adjacent ones of the core pieces are abutted against and connected to each other. When the yoke portion of each core piece has side surfaces that extend radially straight as in PTL 1, it is difficult to position the yoke portions of the adjacent ones of the core pieces relative to each other. For example, the core pieces may be assembled into an annular shape such that the adjacent ones of the core pieces are radially displaced from each other.
An object of the present disclosure is to provide a core that is easy to assemble. Another object of the present disclosure is to provide a stator including the core. Another object of the present disclosure is to provide a rotary electric machine including the stator.
The core according to the present disclosure is easy to assemble. The stator according to the present disclosure includes the core that is easy to assemble. The rotary electric machine according to the present disclosure is easy to produce.
The inventors of the present disclosure have arrived at the idea of forming a protrusion on one side surface of the yoke portion of each core piece and a recess corresponding to the protrusion on the other side surface, so that the yoke portions of adjacent ones of the core pieces can be positioned relative to each other by fitting the protrusion and the recess together. The inventors of the present disclosure have conducted intensive studies and found that, when a core piece including a yoke portion having a protrusion on a side surface thereof is composed of a dust core and is formed by using a mold, a die for forming a peripheral surface of the yoke portion receives a large stress in a region corresponding to the side surface of the yoke portion. When the die receives an excessive stress, breakage of the die may occur. Therefore, it is important to design the protrusion on the side surface of the yoke portion such that the load placed on the die is as small as possible. The inventors of the present disclosure have further conducted intensive studies and found that, as described below, the stress applied to the die can be reduced by forming a plurality of protrusions on a side surface of the yoke portion and setting the interval between the protrusions to 80% or less of the length of the side surface of the yoke portion.
The present disclosure has been made based on the above-described findings. Embodiments of the present disclosure will now be described.
(1) A core according to an embodiment of the present disclosure is for use in an axial-gap rotary electric machine. The core is annular and includes a plurality of core pieces into which the core is divided in a circumferential direction. Each core piece includes a yoke portion and a tooth portion that is formed integrally with the yoke portion and that projects from the yoke portion in an axial direction. Each yoke portion includes a plurality of protrusions provided on one side surface that is connected to the yoke portion of an adjacent one of the core pieces, and a plurality of recesses provided on other side surface that is connected to the yoke portion of another adjacent one of the core pieces, the recesses corresponding to the protrusions. An interval between the protrusions is 80% or less of a length of the one side surface of the yoke portion, the length being a direct distance between inner and outer peripheries of the yoke portion.
According to the core of the present disclosure, adjacent ones of the core pieces can be easily positioned relative to each other, and the core is easy to assemble. The reason for this is that since the yoke portion of each core piece has the plurality of protrusions on one side surface and the plurality of recesses on the other side surface, the yoke portions of adjacent ones of the core pieces can be positioned relative to each other by fitting the protrusions to the recesses. Thus, according to the core of the present disclosure, the core pieces can be assembled into an annular shape with less radial displacements between the core pieces that are adjacent to each other.
When the core pieces are dust cores, the core pieces composed of the dust cores may be formed by compression molding by using soft magnetic powder, which is a collection of a plurality of soft magnetic particles. When each core piece is formed by using a mold, since the interval between the protrusions on one side surface of the yoke portion is 80% or less of the length of the one side surface of the yoke portion, stress applied to a side surface of a die for forming the one side surface of the yoke portion can be reduced. Thus, load placed on the die can also be reduced, so that the possibility of breakage of the die can be reduced. The meaning of the interval between the protrusions and the reason why the stress applied to the die can be reduced will be described below.
(2) According to one embodiment of the above-described core, in plan view of each yoke portion from a side toward which the tooth portion projects, a distance from the recesses to a bottom of the tooth portion is 20% or more of a distance from a reference line to the bottom of the tooth portion, the reference line being a middle line between a side surface of the tooth portion and a side surface of the tooth portion of the other adjacent one of the core pieces, the side surfaces facing each other.
According to this embodiment, since each core piece is structure such that the distance from the recesses to the bottom of the tooth portion is 20% or more of the distance from the reference line to the bottom of the tooth portion, a certain interval is provided between each of the recesses and the bottom of the tooth portion on a surface of the yoke portion at a side at which the tooth portion projects. Accordingly, when each core piece is a dust core and is formed by using a mold, reduction in the strength of a punch for forming the surface of the yoke portion at the side at which the tooth portion projects due to reduction in the thickness of the punch can be suppressed.
(3) According to another embodiment of the above-described core, the protrusions have a size of 1 mm or more and 10 mm or less.
According to this embodiment, since the protrusions have a size of 1 mm or more, the yoke portions of the adjacent ones of the core pieces can be easily positioned relative to each other. When each core piece is a dust core, since the protrusions have a size of 10 mm or less, the core piece can be easily formed. The meaning of the size of the protrusions will be described below.
(4) According to another embodiment of the above-described core, in plan view of each yoke portion from a side toward which the tooth portion projects, a minimum radius of curvature of the protrusions and the recesses is 1.0 mm or more.
According to this embodiment, when each core piece is a dust core, the possibility of breakage of the die can be reduced. The reason for this is that since the minimum radius of curvature of the protrusions and the recesses is 1.0 mm or more, when the core piece is formed by using a mold, stress concentration at the die for forming the side surfaces of the yoke portion can be reduced.
(5) According to another embodiment of the above-described core, adjacent ones of the protrusions have shapes that are symmetrical about a center line between the adjacent ones of the protrusions.
According to this embodiment, when each core piece is a dust core, the possibility of breakage of the die can be more effectively reduced. The reason for this is that since the adjacent ones of the protrusions have shapes that are symmetrical, when the core piece is formed by using a mold, stress applied to the die can be effectively reduced.
(6) According to another embodiment of the above-described core, each yoke portion has a thickness of 1.0 mm or more and 10 mm or less.
The above-described core may be formed by assembling the core pieces into an annular shape and fitting and fixing an annular member to outer peripheral surfaces of the yoke portions to fasten the core pieces together. When the yoke portions have a thickness of 1.0 mm or more, the annular member can be easily fixed, and an appropriate fastening force can be easily applied. When each yoke portion is excessively thick, large load is placed on the die. Therefore, the thickness of each yoke portion is set to 10 mm or less.
(7) According to another embodiment of the above-described core, each core piece is formed of a dust core. The dust core is made of a collection of a plurality of coated soft magnetic particles, which are soft magnetic particles having insulating coatings on surfaces thereof. The soft magnetic particles are iron-based particles composed of at least one of pure iron and an iron-based alloy. The iron-based alloy is at least one selected from a group consisting of an Fe—Si-based alloy, an Fe—Al-based alloy, an Fe—Cr—Al-based alloy, and an Fe—Cr—Si-based alloy.
Pure iron and the above-described iron-based alloy are relatively soft. Therefore, when the soft magnetic particles that constitute the dust core are iron-based particles composed of pure iron or the above-described iron-based alloy, the soft magnetic particles are easily deformed when the dust core is formed. Accordingly, in this embodiment, a high-density dust core having a high dimensional accuracy can be obtained. When a high-density dust core is used, the mechanical strength and magnetic properties of the core piece can be improved. When the soft magnetic particles have insulating coatings on the surfaces thereof, the electrical insulation between the soft magnetic particles can be increased. Therefore, iron loss of the core piece due to eddy current loss can be reduced.
(8) According to an embodiment of the core described in (7), the insulating coatings include phosphate coatings.
The phosphate coatings are highly adhesive to the iron-based particles, and are easily deformed. Therefore, when the insulating coatings include the phosphate coatings, the insulating coatings easily follow the deformation of the iron-based particles when the dust core is formed. Accordingly, in this embodiment, the insulating coatings are not easily damaged, and the iron loss of the core piece can be reduced.
(9) According to an embodiment of the core described in (7) or (8), the dust core has a relative density of 90% or more.
When the relative density of the dust core is 90% or more, the dust core has a high density. According to this embodiment, since the dust core has a high density, the mechanical strength and magnetic properties of the core piece can be improved.
(10) According to another embodiment of the above-described core, the core further includes an annular member fitted to outer peripheral surfaces of the yoke portions of the plurality of core pieces, and the annular member is fixed to the plurality of core pieces by radially inward contraction force thereof.
When the core includes the annular member fitted to the outer peripheral surfaces of the yoke portions, the core pieces that are assembled in an annular shape can be integrated together. In addition, the outer peripheries of the yoke portions are fastened by the radially inward contraction force of the annular member, so that the core pieces can be strongly fastened together.
(11) According to another embodiment of the above-described core, the side surfaces of the yoke portions of the core pieces that are adjacent to each other are bonded to each other. Alternatively, the core includes a plate-shaped member disposed on the yoke portions of the core pieces that are adjacent to each other at a side opposite to a side at which the tooth portions project, and surfaces of the yoke portions at the opposite side are bonded to the plate-shaped member.
When the side surfaces of the yoke portions of the core pieces that are adjacent to each other are bonded to each other or when the surfaces of the yoke portions at the side opposite to the side at which the tooth portions project are bonded to the plate-shaped member, the core pieces that are assembled in an annular shape can be integrated together.
(12) According to another embodiment of the above-described core, a difference between a position of an end surface of a highest one of the tooth portions of the plurality of core pieces and a position of an end surface of a lowest one of the tooth portions of the plurality of core pieces is 0.15 mm or less.
When the surfaces of the yoke portions at the side opposite to the side at which the tooth portions project are placed on a flat surface and when the difference between the position of the end surface of the highest tooth portion and the position of the end surface of the lowest tooth portion is 0.15 mm or less, variation in height between the end surfaces of the tooth portions is small. When the above-described core is included in a rotary electric machine, the end surfaces of the tooth portions are arranged to face magnets of a rotor. When the variation in height between the end surfaces of the tooth portions is small, the rotary electric machine can be structured such that variation in the interval between the end surface of each tooth portion and the rotor is small. Therefore, degradation of the properties of the rotary electric machine can be suppressed. For example, cogging can be reduced.
(13) According to another embodiment of the above-described core, when the plurality of core pieces are assembled in an annular shape, a deviation from roundness of outer peripheral surfaces of the yoke portions is 0.1 mm or less.
When the deviation from roundness of the outer peripheral surfaces of the yoke portions is 0.1 mm or less, the core has a high dimensional accuracy.
(14) According to another embodiment of the above-described core, a deviation from flatness of an end surface of each tooth portion is 0.2 mm or less.
When the deviation from flatness of the end surface of each tooth portion is 0.2 mm or less, the rotary electric machine can be structured such that the end surfaces of the tooth portions closely face the rotor. Accordingly, degradation of the properties of the rotary electric machine can be suppressed.
(15) A stator according to an embodiment of the present disclosure is a stator for an axial-gap rotary electric machine, and includes the core according to any one of (1) to (14) and a coil disposed on each of the tooth portions of the core pieces that constitute the core.
The core included in the stator of the present disclosure is easy to assemble. The core is easy to assemble because the adjacent ones of the core pieces can be easily positioned relative to each other.
(16) A rotary electric machine according to an embodiment of the present disclosure includes a rotor and a stator. The rotary electric machine is an axial-gap rotary electric machine in which the rotor and the stator are arranged to face each other in an axial direction, and the stator is the stator according to (15).
The rotary electric machine according to the present disclosure is easy to produce. This is because the stator included in rotary electric machine includes the core that is easy to assemble.
A core, a stator, and a rotary electric machine according to an embodiment of the present disclosure will now be described with reference to the drawings. In the drawings, components denoted by the same reference signs are those having the same names. The present invention is not limited to the examples described below. The present invention is defined by the scope of the claims, and is intended to include equivalents to the scope of the claims and all modifications within the scope.
<Core>
A core 1 according to an embodiment and core pieces 10 that constitute the core 1 will be described with reference to
In this example, as illustrated in
(Core Piece)
As illustrated in
(Yoke Portion)
The yoke portion 11 is a fan-shaped plate portion of the core piece 10. The yoke portion 11 has fan-shaped flat surfaces, and the tooth portions 12 project from one of the flat surfaces. The one of the flat surfaces is an upper surface. The yoke portion 11 has an arc-shaped inner peripheral surface, an arc-shaped outer peripheral surface, and the side surfaces 20 and 30. The arc-shaped inner peripheral surface and the arc-shaped outer peripheral surface are concentric.
(Tooth Portions)
The tooth portions 12 are portions that are formed integrally with the yoke portion 11 and that project in the axial direction from the one of the flat surfaces, that is, the upper surface, of the yoke portion 11. The axial direction is a direction orthogonal to the radial and circumferential directions of the core 1, more specifically, a direction perpendicular to the upper surface of the yoke portion 11. The tooth portions 12 may be columnar bodies, which may be, for example, polygonal columnar bodies, cylindrical bodies, or elliptic cylindrical bodies. Examples of polygonal columnar bodies include triangular columnar bodies and trapezoidal columnar bodies. In this example, the tooth portions 12 are triangular columnar bodies, and include end surfaces 41 having a triangular shape, more specifically, the shape of an isosceles triangle. The tooth portions 12 may instead be trapezoidal columnar bodies, and the end surfaces 41 may have, for example, a trapezoidal shape. The terms “triangular” and “trapezoidal” do not necessarily refer to shapes that are perfectly geometrically triangular or trapezoidal, and cover substantially triangular or trapezoidal shapes, such as those having rounded corners.
The number of tooth portions 12 included in each core piece 10 may be one or more. In this example, two tooth portions 12 (12a and 12b) are provided. One of the tooth portions 12 that is positioned adjacent to the side surface 20 of the yoke portion 11 is defined as the tooth portion 12a, and the other of the tooth portions 12 that is positioned adjacent to the side surface 30 is defined as the tooth portion 12b.
One characteristic of the core 1 is that, as illustrated in
<Protrusions and Recesses>
The yoke portion 11 includes the protrusions 21 and 22 provided on one side surface 20 and the recesses 31 and 32 provided on the other side surface 30. The shape of the protrusions 21 and 22 on the side surface 20 and the shape of the recesses 31 and 32 on the side surface 30 correspond to each other. A recess 23 is provided between the protrusions 21 and 22, and a protrusion 33 is provided between the recesses 31 and 32. In this example, the protrusions 21 and 22 and the recesses 31 and 32 have the same arc shape and the same size. As illustrated in
In this example, the number of protrusions 21 and 22 and the number of recesses 31 and 32 are two. The number of protrusions 21 and 22 and the number of recesses 31 and 32 may be changed as appropriate, and may be three or more. The shape of the protrusions 21 and 22 and the shape of the recesses 31 and 32 may also be changed as appropriate, and may be, for example, a rectangular shape or a triangular shape. In this example, the protrusions 21 and 22 have the same shape. However, the protrusions 21 and 22 may instead have different shapes.
<Interval between Protrusions>
The interval between the protrusions 21 and 22 is 80% or less of the length of the side surface 20 of the yoke portion 11. The definition of the interval between the protrusions 21 and 22 will now be described. In this example, as illustrated in
When the interval between the protrusions 21 and 22, which is the distance between points a and b in
The ratio of the interval between the protrusions 21 and 22 to the yoke-portion side length may be 70% or less, or 50% or less. The interval between the protrusions 21 and 22 may be, for example, 40 mm or less, or 30 mm or less. The protrusions 21 and 22 cannot be easily formed when the interval therebetween is excessively small. Therefore, the lower limit of the interval between the protrusions 21 and 22 may be, for example, about 1.0 mm.
<Adjacent Protrusions Having Symmetrical Shapes>
In this example, the adjacent protrusions 21 and 22 have shapes that are symmetrical about a center line between the protrusions 21 and 22. As illustrated in
<Distance from Recesses to Bottom of Tooth>
In this example, the distance from the recesses 31 and 32 to the bottom of the tooth portion 12 (12b) is 20% or more of the distance from a reference line denoted by LB in
Assuming that the above-described middle line LB is the reference line, the ratio of the distance from the recesses 31 and 32 to the bottom of the tooth portion 12 (12b) to the distance from the reference line to the bottom of the tooth portion 12 (12b) is 20% or more. In
The ratio of the distance from the recesses 31 and 32 to the bottom of the tooth portion 12 (12b) to the distance from the reference line to the bottom of the tooth portion 12 (12b) may instead be 30% or more. Although there is no particular upper limit on the ratio of the distance from the recesses 31 and 32 to the bottom of the tooth portion 12 (12b), the upper limit may be, for example, 90%. The distance from the recesses 31 and 32 to the bottom of the tooth portion 12 (12b) may be, for example, 1 mm or more and 9 mm or less, or 2 mm or more and 8 mm or less.
<Size of Protrusions>
In this example, the size of the protrusions 21 and 22 is 1 mm or more and 10 mm or less. The size of the protrusions 21 and 22 is defined as follows. That is, referring to
When the size of the protrusions 21 and 22 is 1 mm or more, the yoke portions 11 of adjacent ones of the core pieces 10 can be easily positioned relative to each other. When the size of the protrusions 21 and 22 is 10 mm or less, the protrusions 21 and 22 can be easily formed. The size of the protrusions 21 and 22 may instead be 2 mm or more and 8 mm or less.
<Minimum Radius of Curvature of Protrusions and Recesses>
In this example, in plan view of each yoke portion 11 from above, that is, from the upper side toward which the tooth portions 12 project, the minimum radius of curvature of the protrusions 21 and 22 and the recesses 31 and 32 is 1.0 mm or more. When the protrusions 21 and 22 and the recesses 31 and 32 are shaped to have curves with small radii of curvature, the side surfaces 52, 53 (see
The minimum radius of curvature of the protrusions 21 and 22 and the recesses 31 and 32 may instead be 2.0 mm or more. Although there is no particular upper limit on the minimum radius of curvature of the protrusions 21 and 22 and the recesses 31 and 32, the upper limit may be, for example, 20 mm.
<Thickness of Yoke Portions>
The thickness of each yoke portion 11 is, for example, 1.0 mm or more and 10 mm or less, or 2 mm or more and 8 mm or less. The thickness of each yoke portion 11 is the dimension of the yoke portion 11 in the axial direction of the core 1. In
<Deviation from Roundness of Yoke Portions>
When the core 1 is formed by assembling the core pieces 10 into an annular shape, the deviation from roundness of the outer peripheral surfaces of the yoke portions 11 is preferably 0.1 mm or less. When the deviation from roundness of the outer peripheral surfaces of the yoke portions 11 is 0.1 mm or less, the core 1 has a high dimensional accuracy. Therefore, when the annular member 90 (see
<Heights of End Surfaces of Tooth Portions>
The core 1 is preferably structured such that the difference between the position of the end surface 41 of the highest one of the tooth portions 12 of the core pieces 10 and the position of the end surface 41 of the lowest one of the tooth portions 12 of the core pieces 10 is 0.15 mm or less. Referring to
<Deviation from Flatness of End Surface of Each Tooth Portion>
The deviation from flatness of the end surface 41 of each tooth portion 12 is preferably 0.2 mm or less. In this case, the rotary electric machine 300 (see
In this example, the side surfaces of the yoke portions 11 of the core pieces 10 that are adjacent to each other are bonded to each other so that the core pieces 10 assembled in an annular shape are integrated together. As illustrated in
As illustrated in
When the annular member 90 is provided, the core pieces 10 can be integrated together. In addition, the outer peripheries of the yoke portions 11 are fastened by the radially inward contraction force of the annular member 90, so that the core pieces 10 can be strongly fastened together. One or both of the plate-shaped member 80 and the annular member 90 described above may be used.
<Dust Core>
Each core piece 10 is formed of a dust core. The dust core is formed by compression molding by using soft magnetic powder. The soft magnetic powder is a collection of a plurality of coated soft magnetic particles, which are soft magnetic particles having insulating coatings on the surfaces thereof. Thus, the dust core is composed of a collection of a plurality of coated soft magnetic particles. The soft magnetic particles are preferably iron-based particles composed of at least one of pure iron and an iron-based alloy. Pure iron is defined as iron having a purity of 99 mass % or more. The iron-based alloy may be at least one selected from the group consisting of an iron-silicon (Fe—Si) based alloy, an iron-aluminum (Fe—Al) based alloy, an iron-chromium-aluminum (Fe—Cr—Al) based alloy, and an iron-chromium-silicon (Fe—Cr—Si) based alloy. The soft magnetic particles that form the dust core may be only particles composed of pure iron, only particles composed of an iron-based alloy, or mixed particles containing particles composed of pure iron and particles composed of an iron-based alloy. The insulating coatings may be, for example, phosphate coatings or silica coatings.
Pure iron and the above-described iron-based alloy are relatively soft. Therefore, when the soft magnetic particles are iron-based particles composed of pure iron or the above-described iron-based alloy, the soft magnetic particles are easily deformed when the dust core is formed. Accordingly, a high-density dust core having a high dimensional accuracy can be obtained. When a high-density dust core is used, the mechanical strength and magnetic properties of the core piece 10 can be improved. When the soft magnetic particles have insulating coatings on the surfaces thereof, the electrical insulation between the soft magnetic particles can be increased. Therefore, iron loss of the core piece 10 due to eddy current loss can be reduced.
The insulating coatings preferably include phosphate coatings. The phosphate coatings are highly adhesive to the iron-based particles, and are easily deformed. Therefore, when the insulating coatings include the phosphate coatings, the insulating coatings easily follow the deformation of the iron-based particles when the dust core is formed. Accordingly, the insulating coatings are not easily damaged, and the iron loss of the core piece 10 can be reduced.
The relative density of the dust core is preferably 90% or more. When a high-density dust core is used, the mechanical strength and magnetic properties of the core piece 10 can be improved. More preferably, the relative density is 93% or more. The relative density is the ratio (%) of the actual density of the dust core to the true density of the dust core. The true density is a theoretical density determined by assuming that no internal voids are present. The true density of the dust core can also be determined from the true density of the soft magnetic powder that is used. The relative density of the dust core is calculated as [(molding density of dust core/true density of dust core)×100]. To determine the molding density of the dust core, the dust core is immersed in oil so that the dust core is impregnated with the oil. The molding density of the dust core can be calculated as [oil-impregnated density×(mass of dust core before impregnation with oil/mass of dust core impregnated with oil)]. The oil-impregnated density is a value obtained by dividing the mass of the dust core impregnated with the oil by the volume of the dust core. The volume of the dust core can be measured typically by a liquid displacement method.
The core piece 10 composed of the dust core may be formed by using, for example, the mold 5 illustrated in
To form the core piece 10 by using the mold 5, the lower punch 70 is fitted to the die hole 51 in the die 50, and then the die hole 51 is filled with the soft magnetic powder. Then, the core piece 10 is formed by compressing the soft magnetic powder with the upper punch 60 and the lower punch 70.
The average particle diameter of the soft magnetic powder may be, for example, 20 μm or more and 300 μm or less, or 40 μm or more and 250 μm or less. When the average particle diameter of the soft magnetic powder is in the above-described ranges, the soft magnetic powder is easy to handle and can be easily compressed. The average particle diameter of the soft magnetic powder, which is measured by using a laser diffraction/dispersion particle-diameter/particle-size-distribution analyzer, means the particle diameter at which the cumulative mass is 50% of the mass of all particles.
The density of the core piece 10 can be increased by increasing the molding pressure applied to compress the soft magnetic powder. The molding pressure may be, for example, 700 MPa or more, or 2000 MPa or more.
As illustrated in
When the material powder is compressed to form the core piece 10, the die 50 receives stress in directions such that the die hole 51 expands. As illustrated in
In the molding process, the recess 533 on the side surface 53 of the die 50 is pressed by the material powder such that the recess 533 expands. Since the recess 533 is disposed between the protrusions 531 and 532, which are separated from the outer peripheral edge of the die 50 by a large distance, damage to the mold by the stress does not easily occur.
<Stator>
A stator 100 according to the embodiment will be described with reference to
<Rotary Electric Machine>
The rotary electric machine 300 according to the embodiment will be described with reference to
The stator 100 and the rotor 200 are disposed in a cylindrical casing 310. Disc-shaped plates 320 are attached to both ends of the casing 310. Each plate 320 has a through hole at the center thereof, and a rotating shaft 330 extends through the casing 310.
(Rotor)
The rotor 200 includes a plurality of flat plate-shaped magnets 220 and a circular annular retaining plate 210 that supports the magnets 220. The shape of the magnets 220 in plan view substantially corresponds to the shape of the end surfaces 41 of the tooth portions 12. When the end surfaces 41 of the tooth portions 12 are triangular, the magnets 220 may be, for example, triangular or trapezoidal in plan view. The retaining plate 210 is fixed to the rotating shaft 330 and rotates together with the rotating shaft 330. The magnets 220 are embedded in the retaining plate 210. The magnets 220 are arranged at equal intervals in the circumferential direction of the rotating shaft 330. The magnets 220 are magnetized in the axial direction of the rotating shaft 330. The magnets 220 that are adjacent to each other in the circumferential direction are magnetized in the opposite directions.
(Stator)
The stator 100 is disposed such that the end surfaces 41 of the tooth portions 12 face the magnets 220 of the rotor 200. The outer peripheral surfaces of the yoke portions 11 of the core 1 are fitted to the inner peripheral surface of the casing 310, so that the stator 100 is fixed to the casing 310. A circular annular bearing 340 that supports the rotating shaft 330 in a rotatable manner is attached to the inner peripheral surfaces of the yoke portions 11.
The core 1, the stator 100, and the rotary electric machine 300 according to the above-described embodiment have the following advantageous effects.
Each of the core pieces 10 that constitute the core 1 is structured such that the yoke portion 11 has the plurality of protrusions 21 and 22 on one side surface 20 and the plurality of recesses 31 and 32 corresponding to the protrusions 21 and 22 on the other side surface 30. Therefore, when the core pieces 10 are assembled into an annular shape, the yoke portions 11 of the adjacent ones of the core pieces 10 can be positioned relative to each other by fitting the protrusions 21 and 22 to the recesses 31 and 32. Therefore, radial displacements between the core pieces 10 that are adjacent to each other can be reduced. Accordingly, the core pieces 10 that are adjacent to each other can be easily positioned relative to each other, and the core 1 is easy to assemble.
The stator 100 includes the above-described core 1, and is therefore easy to assemble. The rotary electric machine 300 includes the stator 100 that is easy to assemble, and is therefore easy to produce.
Distribution of the stress applied to the die 50 when the above-described core piece 10 of the embodiment is formed by using the mold 5 was analyzed by computer aided engineering (CAE).
The stress analysis was performed by using “NX Nastran” manufactured by Siemens AG. The analysis conditions were set as follows. That is, the molding pressure was set to 980 MPa. With regard to physical property values of the die 50, the Young's modulus was set to 206000 MPa, and the Poisson's ratio was set to 0.3.
The core piece 10 was designed to have the following dimensions:
The maximum stress applied to the protrusion 523 on the side surface 52 of the die 50 was determined based on the result of the stress analysis by CAE. In Test Example 1, the interval between the protrusions 21 and 22 was changed to change the ratio of the interval between the protrusions to the yoke-portion side length, and the maximum stress was determined for each ratio. The results are shown in Table 1.
It is clear from Table 1 that the maximum stress applied to the protrusion of the die in the molding process decreases as the interval between the protrusions decreases. In particular, when the interval between the protrusions is 80% or less of the yoke-portion side length, the maximum stress applied to the protrusion can be reduced to 1500 MPa or less.
Core pieces having the same structure as that of the above-described core pieces 10 of the embodiment were manufactured and evaluated.
The core pieces 10 were designed to have the following dimensions:
Soft magnetic powder used as the material was powder of coated soft magnetic particles, which were pure iron particles having phosphate coatings on the surfaces thereof. The average particle diameter of the soft magnetic powder was 50 μm. The molding pressure was 980 MPa. The relative density of the core pieces 10 composed of the obtained dust cores was 92%.
Six core pieces 10 were manufactured under the same conditions, and were assembled into a circular annular shape to form the core 1. Each core piece 10 included two tooth portions 12. The total number of tooth portions 12 was twelve. The obtained core 1 was evaluated as follows.
<Deviation from Roundness of Yoke Portions>
The deviation from roundness of the outer peripheral surfaces of the yoke portions was measure by using a commercially available 3D shape measuring device. More specifically, the deviation from roundness was measured by point measurement by using “VR-3200” manufactured by Keyence Corporation. As a result, the deviation from roundness of the outer peripheral surfaces of the yoke portions was 0.1 mm or less.
<Deviation from Flatness of End Surface of Each Tooth Portion>
The deviation from flatness of the end surface of each tooth portion was measured by using a commercially available 3D shape measuring device, more specifically, “VR-3200” manufactured by Keyence Corporation. As a result, the deviation from flatness was 0.1 mm or less for each of the end surfaces of the twelve tooth portions.
<Heights of End Surfaces of Tooth Portions>
The lower surfaces of the yoke portions were placed on a flat surface, and the height positions of the end surfaces of the twelve tooth portions were measured by using a commercially available 3D shape measuring device, more specifically, “VR-3200” manufactured by Keyence Corporation, and the difference between the position of the end surface of the highest tooth portion and the position of the end surface of the lowest tooth portion was determined. The difference was 0.15 mm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-228584 | Dec 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/040974 | 10/17/2019 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/116038 | 6/11/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6445105 | Kliman | Sep 2002 | B1 |
| 7592733 | Naitou | Sep 2009 | B2 |
| 7906886 | Jang | Mar 2011 | B2 |
| 8736133 | Smith | May 2014 | B1 |
| 9391500 | Smith | Jul 2016 | B2 |
| 10135310 | Schuler | Nov 2018 | B2 |
| 10170953 | Shaw | Jan 2019 | B2 |
| 10186922 | Schuler | Jan 2019 | B2 |
| 10886796 | Stetina | Jan 2021 | B2 |
| 11018565 | Post | May 2021 | B2 |
| 20050073213 | Naito | Apr 2005 | A1 |
| 20110273048 | Jore | Nov 2011 | A1 |
| 20110316381 | Asano | Dec 2011 | A1 |
| 20150155070 | Cao | Jun 2015 | A1 |
| 20150214801 | Libault | Jul 2015 | A1 |
| 20170126108 | Tokoi | May 2017 | A1 |
| 20170155290 | Sakai et al. | Jun 2017 | A1 |
| 20180175707 | Miyama | Jun 2018 | A1 |
| 20190013708 | Hattori | Jan 2019 | A1 |
| 20190214860 | Igarashi et al. | Jul 2019 | A1 |
| 20190252930 | Stetina | Aug 2019 | A1 |
| 20190260255 | Kuwahara | Aug 2019 | A1 |
| 20200328634 | Mihaila | Oct 2020 | A1 |
| 20210091608 | Hull | Mar 2021 | A1 |
| 20210091647 | Maruyama | Mar 2021 | A1 |
| 20210143696 | Guedes-Pinto | May 2021 | A1 |
| 20210152040 | Yao | May 2021 | A1 |
| 20220045582 | Hunstable | Feb 2022 | A1 |
| 20220060065 | Wu | Feb 2022 | A1 |
| 20220239177 | Hillman | Jul 2022 | A1 |
| 20220239210 | Hillman | Jul 2022 | A1 |
| 20220302773 | Leijnen | Sep 2022 | A1 |
| 20230048820 | Yao | Feb 2023 | A1 |
| Number | Date | Country |
|---|---|---|
| 203151249 | Aug 2013 | CN |
| 114243982 | Mar 2022 | CN |
| 115333262 | Nov 2022 | CN |
| 102021102807 | Sep 2021 | DE |
| 3174183 | May 2017 | EP |
| 2008-35599 | Feb 2008 | JP |
| 2008035599 | Feb 2008 | JP |
| 2008-125278 | May 2008 | JP |
| 2010088166 | Apr 2010 | JP |
| 2011-135626 | Jul 2011 | JP |
| 2017-229191 | Dec 2017 | JP |
| WO-2011065080 | Jun 2011 | WO |
| 2015145901 | Oct 2015 | WO |
| 2017221512 | Dec 2017 | WO |
| Entry |
|---|
| International Search Report and Written Opinion dated Feb. 4, 2020, received for PCT Application PCT/JP2019/040974, Filed on Oct. 17, 2019, 11 pages including English translation. |
| Number | Date | Country | |
|---|---|---|---|
| 20210344238 A1 | Nov 2021 | US |
