Rotary electric machine

Abstract

To provide a rotary electric machine which is excellent in productivity and has low energy loss.SOLUTION: Disclosed is an axial gap type rotary electric machine in which a first stator, a second stator, and a rotor are aligned in the axial direction of a rotation shaft of the rotor. The first stator has a first core made of a dust core on which a first coil is disposed. The second stator has a second core made of a dust core on which a second coil is disposed. The first core has a first annular yoke and a plurality of first teeth. The second core has a second annular yoke and a plurality of second teeth. The highest tooth on the first core and the lowest tooth on the second core are disposed so as to face each other.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This disclosure relates to a rotating electric machine. This application claims priority to Japanese Patent Application No. 2019-190556, filed on October 17, 2019, and incorporates by reference all of the contents of that application. [Background technology]

[0002] As an axial gap type rotating electric machine (motor / generator), FIG. 13 of Patent Document 1 discloses a double stator type rotating electric machine in which a rotor is sandwiched between a pair of stators. The stator has a core in which a coil is arranged. The core has a disk-shaped yoke and a plurality of teeth protruding from one side of the yoke. Coils are arranged around the outer periphery of the teeth. In Patent Document 1, the stator core is formed by providing holes in the yoke and fitting columnar teeth into the holes. Meanwhile, the rotor has a plurality of permanent magnets.

[0003] In an axial gap type rotating electric machine equipped with a pair of stators, the stators are arranged in the axial direction of the rotor's rotation shaft in the order of one stator, the rotor, and the other stator, with the teeth of one stator facing the teeth of the other stator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007 / 114079 Summary of the Invention

[0005] The rotating electric machine of the present disclosure is an axial gap type rotating electric machine in which a first stator, a second stator, and a rotor are arranged in an axial direction of a rotation shaft of the rotor, the first stator includes a first coil and a first core formed of a powder magnetic core on which the first coil is disposed, the second stator includes a second coil and a second core formed of a powder magnetic core on which the second coil is disposed, The first core is a first yoke having a circular ring shape and a first yoke surface; a plurality of first teeth projecting from the first yoke surface toward the rotor and integrally formed with the first yoke; a first mark indicating a reference position in the circumferential direction of the first yoke, The second core is a second yoke having an annular shape and a second yoke surface facing the first yoke surface; a plurality of second teeth projecting from the second yoke surface toward the rotor and integrally formed with the second yoke; a second mark indicating a reference position in the circumferential direction of the second yoke, When viewed in the axial direction of the rotation shaft, the first mark and the second mark are disposed at positions symmetrical to each other with respect to the rotation shaft. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a partial vertical cross-sectional view of an axial gap type rotating electrical machine according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a first core of the first stator. [Figure 3] FIG. 3 is a top view of the first core of the first stator. [Figure 4] FIG. 4 is a top view of the second core of the second stator. [Figure 5] FIG. 5 is a schematic diagram showing the positional relationship between a mold for manufacturing the first teeth and a powder feeder. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the positional relationship between the first teeth, the second teeth, and the rotor. [Figure 8] FIG. 8 is a graph showing the torque ripple of Sample No. 1 described in the test examples. [Figure 9]FIG. 9 is a graph showing the cogging torque of Sample No. 1 described in the Test Examples. [Figure 10] FIG. 10 is a graph showing the torque ripple of Sample No. 2 described in the Test Examples. [Figure 11] FIG. 11 is a graph showing the cogging torque of Sample No. 2 described in the Test Examples. DETAILED DESCRIPTION OF THE INVENTION

[0007] In Patent Document 1, the yoke and teeth are fabricated separately and then combined to fabricate the stator core. With this configuration, the labor required to combine the yoke and teeth is significant, resulting in poor productivity for the rotating electrical machine.

[0008] Furthermore, in the configuration of Patent Document 1, the protruding height of the teeth from the yoke is prone to variation. When the protruding height of the teeth varies, electromagnetic energy loss increases due to factors such as increased torque ripple. Furthermore, the rotor's rotation axis is prone to fluctuation, which increases mechanical energy loss due to factors such as increased friction between the shaft and bearings.

[0009] [Description of the embodiments of the present disclosure] The present inventors have investigated the use of a powder core to form a core having a yoke and multiple teeth. When manufacturing a core using a powder core, a powder feeder is used to fill a mold with magnetic powder and then pressure-molded. A typical powder feeder linearly reciprocates over the mold to feed powder into the mold. The present inventors discovered that a portion of the mold at the powder feed start side tends to be filled with more magnetic powder than a portion at the powder feeder's return side. Furthermore, the present inventors discovered that when a powder feed axis is defined as a line passing through the center of the mold in a top view and along the reciprocating direction of the powder feeder, the magnetic powder filling amounts at portions symmetrically positioned with respect to the powder feed axis tend to be approximately the same. In other words, in a powder core, the height of the multiple teeth provided on the core tends to gradually decrease from the powder feed start side toward the return side of the powder feeder. Furthermore, the protruding heights of teeth symmetrically positioned with respect to the powder feed axis are approximately the same. Based on these findings, the present inventors have completed a rotating electric machine according to an embodiment. Embodiments of the present disclosure will be listed and described below.

[0010] <1> The rotating electric machine according to the embodiment includes: An axial gap type rotating electric machine in which a first stator, a second stator, and a rotor are arranged in an axial direction of a rotation shaft of the rotor, the first stator includes a first coil and a first core formed of a powder magnetic core on which the first coil is disposed, the second stator includes a second coil and a second core formed of a powder magnetic core on which the second coil is disposed, The first core is a first yoke having a circular ring shape and a first yoke surface; a plurality of first teeth projecting from the first yoke surface toward the rotor and integrally formed with the first yoke; a first mark indicating a reference position in the circumferential direction of the first yoke, The second core is a second yoke having an annular shape and a second yoke surface facing the first yoke surface; a plurality of second teeth projecting from the second yoke surface toward the rotor and integrally formed with the second yoke; a second mark indicating a reference position in the circumferential direction of the second yoke, When viewed in the axial direction of the rotation shaft, the first mark and the second mark are disposed at positions symmetrical to each other with respect to the rotation shaft.

[0011] The rotating electric machine has excellent productivity because the first core and the second core of the rotating electric machine are both powder magnetic cores in which the yoke and the teeth are integrally molded, and therefore the step of combining the yoke and the teeth is omitted.

[0012] The rotating electric machine has excellent energy efficiency. The rotating electric machine has a plurality of tooth pairs. Each tooth pair is a set of first and second teeth positioned opposite each other in the axial direction of the rotor. Since the first and second marks are positioned symmetrically with respect to the rotation axis, the inter-teeth distances in all tooth pairs are approximately equal. As a result, the variation in torque provided by each tooth pair at various points around the rotor is reduced. In other words, torque ripple in the rotating electric machine is reduced. Therefore, magnetic energy loss in the rotating electric machine is unlikely to increase. Furthermore, because the torque ripple is small, the rotor's rotation axis is unlikely to wobble. In other words, the frictional force between the rotation axis and the bearing is unlikely to fluctuate. Therefore, it is believed that mechanical energy loss in the rotating electric machine is unlikely to increase. Furthermore, because the torque ripple is small, noise and vibration in the rotating electric machine are suppressed.

[0013] The reason why the distance between the teeth of all pairs of teeth is approximately equal when the first and second marks are positioned symmetrically with respect to the rotation axis of the rotor is because there is line symmetry in the protruding height of the teeth in the core made of powder magnetic core. If a double stator type rotating electric machine is made by combining first and second cores made of powder magnetic core without taking this line symmetry into consideration, there is a risk of large variations in the distance between the teeth.

[0014] The rotating electric machine can be easily assembled because the first and second cores of the rotating electric machine are provided with first and second marks, respectively. The first and second marks may indicate, for example, one end side of the powder feeder in the reciprocating direction (the powder feed start side or the return side of the powder feeder). Alternatively, the first mark may be provided at a position offset by a predetermined length from the one end in the circumferential direction of the first yoke. Alternatively, the second mark may be provided at a position offset by a predetermined length from the one end in the circumferential direction of the second yoke. In any case, if the first and second marks are arranged at positions symmetrical to each other with respect to the rotation axis of the rotor, the first and second cores can be aligned so as to reduce variation in the distance between the teeth.

[0015] <2> As one embodiment of a rotating electric machine according to the present invention, When a first reference line is imaginary on the first yoke, passing through the first mark and the axis of the first yoke as viewed in the axial direction of the first yoke, and a second reference line is imaginary on the second yoke, passing through the second mark and the axis of the second yoke as viewed in the axial direction of the second yoke, a difference in protruding height from the first yoke surface to end faces of the first teeth, the first teeth being symmetrical with respect to the first reference line, is 0.15 mm or less; a difference in protruding height from the second yoke surface to end faces of the second teeth, the difference being 0.15 mm or less, for the second teeth that are positioned symmetrically with respect to the second reference line; The form can be mentioned.

[0016] The first reference line of the first core may be considered to coincide with the powder feed axis when manufacturing the first core. The second reference line of the second core may be considered to coincide with the powder feed axis when manufacturing the second core. The reference line of a core can be determined by measuring the protruding height of each tooth of the core and comparing these protruding heights. For example, consider a core with 12 teeth arranged from 1 o'clock to 12 o'clock, like a clock face. If the teeth at the 12 o'clock position are the tallest and the teeth at the 6 o'clock position are the shortest, it can be inferred that the line connecting the 12 o'clock and 6 o'clock positions is the reference line. In this case, the protruding heights of teeth located symmetrically with respect to the reference line are substantially the same. For example, the height of the teeth at the 1 o'clock position and the height of the teeth at the 11 o'clock position are substantially the same. Furthermore, the height of the teeth is as follows: teeth at 12 o'clock position > teeth at 1 o'clock (11 o'clock) position > teeth at 2 o'clock (10 o'clock) position > teeth at 3 o'clock (9 o'clock) position > teeth at 4 o'clock (8 o'clock) position > teeth at 5 o'clock (7 o'clock) position > teeth at 6 o'clock position. Therefore, if the first mark and second mark are positioned symmetrically with respect to the rotor's rotation axis, the variation in the distance between the teeth in all tooth pairs will be very small.

[0017] <3> As one embodiment of a rotating electric machine according to the present invention, a plurality of tooth pairs each including the first tooth and the second tooth, the first tooth and the second tooth being positioned opposite each other in an axial direction of the rotation shaft; An example of a configuration is one in which the distance between teeth is the distance from the area center of gravity of the end face of the first tooth to the area center of gravity of the end face of the second tooth in each of the multiple tooth pairs, and the difference between the maximum inter-teeth distance and the minimum inter-teeth distance is 0.08 mm or less.

[0018] This rule means that the variation in the inter-tooth distance is 0.08 mm or less. In other words, in a rotating electrical machine with the above configuration, the inter-tooth distances of all tooth pairs are substantially uniform. Therefore, this rotating electrical machine has excellent energy efficiency.

[0019] <4> As one embodiment of a rotating electric machine according to the present invention, a variation in overall height from a surface of the first core opposite to the first yoke surface to an end surface of the first teeth is 0.05 mm or more and 0.15 mm or less, An example of an embodiment is one in which the variation in overall height from the surface of the second core opposite the second yoke surface to the end faces of the second teeth is 0.05 mm or more and 0.15 mm or less.

[0020] As already mentioned, the height of each tooth in a powder magnetic core tends to vary. However, it is preferable for this variation to be small. With the above configuration, the variation in the distance from each first tooth in the first core to the rotor is small, and the variation in the distance from each second tooth in the second core to the rotor is small. In other words, the variation in torque obtained from multiple tooth pairs arranged circumferentially around the rotor is small, thereby reducing torque ripple. Therefore, with the above configuration, the energy efficiency of the rotating electric machine can be improved.

[0021] <5> As one embodiment of a rotating electric machine according to the present invention, The variation in thickness of the first yoke is 0.03 mm or more and 0.10 mm or less, The variation in thickness of the second yoke may be 0.03 mm or more and 0.10 mm or less.

[0022] According to the above configuration, <4> For the same reason, the energy efficiency of the rotating electrical machine can be improved.

[0023] <6> As one embodiment of a rotating electric machine according to the present invention, The variation in the protruding height of the plurality of first teeth is 0.03 mm or more and 0.10 mm or less, An embodiment may include a configuration in which the variation in protruding height of the plurality of second teeth is 0.03 mm or more and 0.10 mm or less.

[0024] According to the above configuration, <4> For the same reason, the energy efficiency of the rotating electrical machine can be improved.

[0025] <7> As one embodiment of a rotating electric machine according to the present invention, the rotor includes a first rotor surface facing an end face of the first teeth and a second rotor surface facing an end face of the second teeth, a variation in overall height from the surface opposite the first yoke surface to the end surface of the first teeth for the plurality of first teeth is 20% or less of an average value of a distance between the plurality of first teeth and the first rotor surface, An example of a form in which the variation in overall height from the opposite surface of the second yoke surface to the end surface of the second teeth for the multiple second teeth is 20% or less of the average value of the distance between the multiple second teeth and the second rotor surface.

[0026] According to the above configuration, <4> For the same reason, the energy efficiency of the rotating electrical machine can be improved.

[0027] <8> As one embodiment of a rotating electric machine according to the present invention, the rotor includes a first rotor surface facing an end face of the first teeth and a second rotor surface facing an end face of the second teeth, a variation in the thickness of the first yoke is 2% or less of an average value of a distance between the first yoke surface and the first rotor surface; An embodiment may be such that the variation in thickness of the second yoke is 2% or less of the average value of the distance between the second yoke surface and the second rotor surface.

[0028] According to the above configuration, the energy efficiency of the rotating electrical machine can be improved.

[0029] <9> As one embodiment of a rotating electric machine according to the present invention, When energized, a ring-shaped magnetic path is formed that passes through the first core, the rotor, and the second core, a variation in overall height from the surface opposite the first yoke surface to the end surface of the first teeth for the plurality of first teeth is 1% or less of the magnetic path length of the annular magnetic path, An example of the embodiment is one in which the variation in overall height of the second teeth from the surface opposite the second yoke surface to the end face of the second teeth is 1% or less of the magnetic path length of the annular magnetic path.

[0030] According to the above configuration, it is possible to improve the energy efficiency of the rotating electrical machine. An example of the annular magnetic path will be described in the embodiment below.

[0031] [Details of the embodiments of the present disclosure] Specific examples of rotating electric machines according to embodiments of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0032] <Embodiment 1> <Rotating electric machines> In the first embodiment, an axial gap type rotating electric machine 100 shown in FIG. 1 will be described as an example. The rotating electric machine 100 may be a generator or an electric motor (motor). The rotating electric machine 100 includes a first stator 1, a second stator 2, and a rotor 3 arranged in a housing 101. The rotating electric machine 100 of this example is a three-phase, four-pole, six-slot rotating electric machine 100. In other words, the rotating electric machine 100 is used with three-phase AC. The rotor 3 is provided with four magnets 32. The first stator 1 has six first teeth 5. The second stator 2 has six second teeth 7. Here, the number of AC phases and the number of poles (the number of magnets 32) are not particularly limited. Furthermore, the number of slots is not particularly limited as long as it is a multiple of the number of phases.

[0033] Rotor The rotor 3 includes a plurality of flat magnets 32 and an annular retaining plate 31 that supports the magnets 32. The retaining plate 31 is fixed to the shaft 30 and rotates together with the shaft 30. The magnets 32 are embedded in the retaining plate 31. The magnets 32 are arranged at intervals in the circumferential direction of the retaining plate 31. The magnets 32 are magnetized in the direction of the rotation axis of the rotor 3 (the axial direction of the shaft 30). The magnetization directions of adjacent magnets 32 in the circumferential direction of the shaft 30 are opposite to each other.

[0034] First stator The first stator 1 includes a first core 10 and a first coil 11. As shown in the perspective view of FIG. 2 and the top view of FIG. 3, the first core 10 includes a first yoke 4 having an annular shape and a plurality of first teeth 5 formed in a cylindrical shape. The shape of the first teeth 5 is not particularly limited. For example, the first teeth 5 may be a roughly triangular prism as shown in FIG. 2. Alternatively, the first teeth 5 may be a cylindrical or rectangular prism. Here, in FIGS. 2 and 3, the first teeth 5 are denoted by reference numerals 51 to 56 so that they can be distinguished from one another. All of the first teeth 51 to 56 protrude from the first yoke surface 40 of the first yoke 4. The first yoke surface 40 is the surface facing the first rotor surface 3A of the rotor 3 shown in FIG. 1.

[0035] The dimensions of the first yoke 4 and the first teeth 5 can be selected appropriately depending on the characteristics required for the rotating electric machine 100. For example, the inner diameter of the first yoke 4 can be 10 mm or more and 100 mm or less, and the outer diameter can be 20 mm or more and 120 mm or less. In addition, the protruding height of the first teeth 5, measured from the first yoke surface 40 to the end face of the first teeth 5, can be 2 mm or more and 40 mm or less, and the area of ​​the cross section perpendicular to the protruding height can be 10 mm or less. 2 Over 800mm 2 It can be as follows:

[0036] In the present example of the rotating electric machine 100 (FIG. 1) used with three-phase AC, the U-phase first coil 11 (FIG. 1) is wound around the first teeth 51 and 54, the V-phase first coil 11 is wound around the first teeth 52 and 55, and the W-phase first coil 11 is wound around the first teeth 53 and 56.

[0037] The first core 10 is a dust core obtained by compacting magnetic powder. Examples of soft magnetic powder include powder of at least one type selected from iron-based alloys such as pure iron (purity of 99% by mass or more), Fe-Si-Al alloys (Sendust), Fe-Si alloys (silicon steel), Fe-Al alloys, and Fe-Ni alloys (Permalloy). The soft magnetic particles preferably have an insulating coating on their surfaces. By forming an insulating coating on the surfaces of the soft magnetic particles, electrical insulation between the soft magnetic particles can be ensured. Examples of insulating coatings include phosphate coatings and silica coatings.

[0038] In the first core 10 made of a powder magnetic core, the height of each first tooth 5 is prone to variation. However, there is a certain rule as to how this variation occurs. This rule is due to the method of manufacturing the first core 10. Therefore, an example of a method of manufacturing the first core 10 will be described with reference to FIGS. 5 and 6 .

[0039] FIG. 5 is a top view of a mold 9 for producing the first core 10 and a powder feeder 8 that supplies magnetic powder to the mold 9. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5. The mold 9 has a yoke forming portion 90, which is a recess provided on its top surface, and tooth forming portions 91-96, which are recesses provided on the bottom surface of the yoke forming portion 90. The yoke forming portion 90 is a mold corresponding to the first yoke 4 in FIGS. 2 and 3. The tooth forming portions 91-96 are molds corresponding to the first teeth 51-56 in FIGS. 2 and 3, respectively. For example, the tooth forming portion 91 is a mold for the first tooth 51, and the tooth forming portion 92 is a mold for the first tooth 52.

[0040] The powder feeder 8 moves in the radial direction of the mold 9. For example, as shown by the hollow arrow, the powder feeder 8 moves from the tooth forming section 91 side to the tooth forming section 94 side to supply magnetic powder 8d into the mold 9. The powder feeder 8 has a wide powder feed opening 80 that runs in a direction perpendicular to the direction of its movement. The width of the powder feed opening 80 (the length in the vertical direction of the paper in Figure 5) is equal to or greater than the opening width of the yoke forming section 90. Powder feeding may be performed only on the outbound path indicated by the hollow arrow, or on both the outbound path and the return path (the direction opposite to the hollow arrow).

[0041] When the powder feeder 8 moves linearly over the mold 9, the amount of magnetic powder 8d filled into each of the tooth forming portions 91-96 tends to vary. Specifically, for example, if the magnetic powder 8d has high fluidity, the portion on the powder feeding start side of the mold 9 (the right side of the drawing) tends to be filled with more magnetic powder than the portion on the return side of the powder feeder 8 (the left side of the drawing). In the example of FIG. 5, the tooth forming portion 91 tends to be filled with more magnetic powder 8d, and the amount of magnetic powder 8d filled decreases toward the tooth forming portion 94. Furthermore, when the powder feeding axis 8s is a straight line passing through the center of the mold 9 in FIG. 5 and aligned with the reciprocating direction of the powder feeder 8, the tooth forming portions 92 and 96, which are positioned symmetrically with each other about the powder feeding axis 8s, tend to be filled with approximately the same amount of magnetic powder 8d. Furthermore, the tooth forming portions 93 and 95, which are positioned symmetrically with each other about the powder feeding axis 8s, tend to be filled with approximately the same amount of magnetic powder 8d. That is, the filling amount of magnetic powder 8d is as follows: tooth forming portion 91 > tooth forming portions 92 and 96 > tooth forming portions 93 and 95 > tooth forming portion 94.

[0042] 5, the powder supply axis 8s is set to pass through the tooth forming portions 91 and 94. Unlike this example, the powder supply axis 8s may be set to pass through the yoke forming portion 90. For example, the powder supply axis 8s may be set to pass between the tooth forming portions 91 and 92 and through the tooth forming portions 94 and 95. In that case, the filling amount of magnetic powder 8d is as follows: tooth forming portions 91 and 92 > tooth forming portions 93 and 96 > tooth forming portions 94 and 95.

[0043] As described above, when a linearly moving powder feeder 8 is used, the amount of magnetic powder filled into the mold 9 tends to be line-symmetrical with respect to the powder feed axis 8s. Therefore, the protruding heights (axial lengths of the first yoke 4) of the first teeth 51-56 of the first core 10 shown in FIGS. 2 and 3 produced using the mold 9 also have line symmetry. That is, a first reference line 1s corresponding to the powder feed axis 8s (FIG. 5) at the time of production of the first core 10 can be imagined for the first core 10. The first reference line 1s is a line extending radially through the axis of the first yoke 4. The heights of the first teeth 51-56 are line-symmetrical with respect to the first reference line 1s. Specifically, the protruding height of the first tooth 51 > the protruding heights of the first teeth 52 and 56 > the protruding heights of the first teeth 53 and 55 > the protruding height of the first tooth 54. The difference in protruding height between the first teeth 52 and the first teeth 56 is 0.02 mm or less, and the protruding heights of the first teeth 52 and the first teeth 56 may be considered to be substantially the same. Also, the difference in protruding height between the first teeth 53 and the first teeth 55 is 0.02 mm or less, and the protruding heights of the first teeth 53 and the first teeth 55 may be considered to be substantially the same. Here, the protruding height h of the first teeth 51 to 56 t 7, the protruding height h of the first teeth 51 to 56 is the length of a straight line that extends perpendicularly from an imaginary plane including the first yoke surface 40 to the center of gravity of the area of ​​the end faces of the first teeth 51 to 56. t The protrusion height h of the first teeth 51 to 56 can be measured using, for example, a one-shot 3D shape measuring machine VR-5000 manufactured by Keyence Corporation. t is calculated from the height profile passing through the center of gravity of the end faces of the first teeth 51 to 56. c can also be measured in the same way.

[0044] The first reference line 1s is the protruding height h of each of the first teeth 51 to 56. t Measure its protruding height h t If the first core 10 is provided with a first mark 15 (FIG. 3) indicating the position of the first reference line 1s, the protrusion height h tThe first mark 15 in this example indicates the powder feeding start side when manufacturing the first core 10. Therefore, in this example, the first mark 15 is the one having the maximum protruding height h t The first marks 15 are provided between the first teeth 51, which are the teeth with the highest protrusion height, and the end of the first yoke 4. More specifically, the first marks 15 are provided on a line connecting the center of gravity of the area of ​​the first teeth 51 and the axis of the first yoke 4, and between the first teeth 51 and the end of the first yoke 4 that is closer to the first teeth 51. The first marks 15 have a maximum protrusion height h t The first mark 15 indicates the highest tooth, and is a reference in the circumferential direction of the first yoke 4. Unlike this example, the first mark 15 may indicate the folded side of the powder feeder 8 (FIGS. 5 and 6). In this case, the first mark 15 has the maximum protruding height h t This indicates the lowest tooth, and is a reference in the circumferential direction of the first yoke 4. In other words, the first mark 15 has the maximum protruding height h t Highest teeth or highest protruding height h t The first mark 15 indicates either a tooth with a high or low value. The same applies to the second mark 25 described later. The first mark 15 can be configured as a recess or a protrusion provided on the first core 10. In this case, it is preferable to form the protrusion or the recess in the mold 9 (FIG. 5). It is preferable to provide the first mark 15 in a position that is unlikely to adversely affect the magnetic properties of the first core 10. The first mark 15 can also be configured as paint or a sticker. In this case, the first mark 15 does not adversely affect the magnetic properties of the first core 10.

[0045] Although there is a tendency for variations in the dimensions of each part of the first core 10 made of a powder magnetic core to occur, it is preferable that the variations in the dimensions of each part be small. For example, as shown in FIG. 7, the total height h from the surface of the first core 10 opposite the first yoke surface 40 to the end faces of each of the first teeth 51 to 56 is c It is preferable that the variation of the total height h is 0.05 mm or more and 0.15 mm or less. c Taking the first tooth 51 as an example, the length of a straight line perpendicular to the underside of the first yoke 4 and extending to the center of gravity of the area of ​​the end face of the first tooth 51 is the length of a straight line perpendicular to the underside of the first yoke 4. In this example, the six overall heights hc That is, the highest h c and the lowest h c It is preferable that the difference between the total height h and the total height h is 0.05 mm or more and 0.15 mm or less. c The variation is preferably 0.13 mm or less, and more preferably 0.10 mm or less.

[0046] The variation in the thickness t of the first yoke 4 is preferably 0.03 mm or more and 0.10 mm or less. The thickness t is the thickness at the center position between two circumferentially adjacent first teeth 51, 52. In this example, the thickness t is measured at six points, the same number as the number of first teeth 5, and it is preferable that the difference between the maximum thickness t and the minimum thickness t be 0.03 mm or more and 0.10 mm or less. The variation in the thickness t is preferably 0.09 mm or less, and more preferably 0.08 mm or less.

[0047] The protruding height h of each of the first teeth 51 to 56 t The variation of the height of the six protrusions h is preferably 0.03 mm or more and 0.10 mm or less. t Therefore, the maximum protrusion height h t and the minimum protrusion height h t The difference between the protrusion height h and the protrusion height h is preferably 0.03 mm or more and 0.10 mm or less. t The variation is preferably 0.09 mm or less, and more preferably 0.08 mm or less.

[0048] Second stator As shown in FIG. 1, the second stator 2 includes a second core 20 and a second coil 21. As shown in FIG. 4, the second core 20 includes an annular second yoke 6 and a plurality of second teeth 71 to 76 protruding from a second yoke surface 60 of the second yoke 6. The second core 20 is manufactured using the same mold 9 (FIGS. 5 and 6) as the first core 10. The second yoke 6, the second yoke surface 60, and the second teeth 71 to 76 are the same as the first yoke 4, the first yoke surface 40, and the first teeth 51 to 56 of the first core 10 shown in FIGS. 2 and 3, respectively. Also, as shown in FIG. 4, the second reference line 2s and the second mark 25 indicating its position are the same as the first reference line 1s of the first core 10 and the first mark 15 indicating its position. That is, in this example, the second mark 25 has a maximum protruding height h t The second marks 25 are provided between the second teeth 71, which are the tallest teeth, and the end of the second yoke 6. More specifically, the second marks 25 are provided on a line connecting the center of gravity of the area of ​​the second teeth 71 and the axis of the second yoke 6, and between the second teeth 71 and the end of the second yoke 6 that is closer to the second teeth 71. A description of each component of the second core 20 will be omitted.

[0049] <<First and second core placement>> When the first core 10 (FIG. 3) and the second core 20 (FIG. 4) that are axially symmetrical are combined, the first mark 15 of the first core 10 and the second mark 25 of the second core 20 are positioned symmetrically with respect to the rotation axis (shaft 30 in FIG. 1) of the rotor 3 when viewed in the axial direction of the rotation axis. By positioning the first mark 15 and the second mark 25 symmetrically with respect to each other, the first reference line 1s and the second reference line 2s coincide with each other. In FIG. 7, the heights of the first teeth 51-54 and the second teeth 71-74 are exaggerated. Furthermore, the distance between the first core 10 and the rotor 3 and the distance between the second core 20 and the rotor 3 are also shown larger than they actually are.

[0050] As shown in FIG. 7 , when the first core 10 and the second core 20 are arranged so that their teeth face each other, teeth pairs are obtained in which the first teeth 51 and the second teeth 74 face each other in the axial direction of the rotation shaft (the direction connecting the centers of the first yoke 4, the rotor 3, and the second yoke 6). In other words, by arranging the first marks 15 and the second marks 25 in symmetrical positions, the highest first teeth 51 of the first core 10 face the lowest second teeth 74 of the second core 20. In addition, teeth pairs of the first teeth 52 and the second teeth 73, the first teeth 53 and the second teeth 72, and the first teeth 54 and the second teeth 71 are obtained. In addition, although they are located in positions not visible in the drawing, teeth pairs of the first teeth 55 and the second teeth 76 and the first teeth 56 and the second teeth 75 are obtained. As already mentioned, the height of the teeth is as follows: teeth 51, 71 > teeth 52, 56, 72, 76 > teeth 53, 55, 73, 75 > teeth 54, 74. Therefore, all tooth pairs are either the highest tooth and the lowest tooth combination, or the second highest tooth and the second lowest tooth combination.

[0051] The variation in the inter-tooth distance L between each tooth pair is 0.08 mm or less. The inter-tooth distance L is the distance between the area center of gravity of the end face of the first tooth and the area center of gravity of the end face of the second tooth in the tooth pair. In other words, one inter-tooth distance L is obtained for one tooth pair. A variation in the inter-tooth distance L of 0.08 mm or less means that the difference between the maximum inter-tooth distance L and the minimum inter-tooth distance L is 0.08 mm or less. In this example, the cores 10 and 20 are combined taking into account the difference in height of each tooth of the cores 10 and 20. Therefore, the difference between the maximum inter-tooth distance L and the minimum inter-tooth distance L is 0.08 mm or less. The smaller this difference, the better. For example, the difference is preferably 0.06 mm or less, and more preferably 0.04 mm or less. It is most preferable that the difference be zero.

[0052] Effect of this embodiment The rotating electric machine 100 of this example has excellent productivity because the first core 10 and the second core 20 of the rotating electric machine 100 are both powder magnetic cores in which the yoke and teeth are integrally molded, thereby eliminating the need to assemble the yoke and teeth.

[0053] The rotating electric machine 100 of this example has excellent energy efficiency. In the rotating electric machine 100 of this example, the inter-tooth distance L of all tooth pairs is approximately equal, so the variation in torque provided by each tooth pair at each point in the circumferential direction of the rotor 3 is small. In other words, the torque ripple in the rotating electric machine 100 is small. Therefore, magnetic energy loss in the rotating electric machine 100 is unlikely to increase. Furthermore, because the torque ripple of the rotating electric machine 100 is small, the rotating shaft (shaft 30) of the rotor 3 is unlikely to vibrate. In other words, the frictional force between the shaft 30 and the bearing 33 is unlikely to fluctuate. Therefore, it is considered that mechanical energy loss in the rotating electric machine 100 is unlikely to increase.

[0054] <Other Provisions> By satisfying the following requirements, the energy efficiency of the rotating electrical machine 100 can be improved.

[0055] The total height h of the first core 10 shown in FIG. c The variation in the distance between each of the first teeth 51 to 56 (FIG. 3) and the first rotor surface 3A is 20% or less of the average value of the distance. The number of measurements of the distance is the same as the number of the first teeth 51 to 56. In addition, the overall height h c The variation in the distance between each of the second teeth 71 to 76 (FIG. 4) and the second rotor surface 3B is 20% or less of the average value of the distance. The number of measurements of the distance is the same as the number of second teeth 71 to 76.

[0056] The variation in the thickness t of the first yoke 4 is 2% or less of the average value of the distance between the first yoke surface 40 and the first rotor surface 3A. This average value is the average value of the linear distance extending in the perpendicular direction from the measurement position of the thickness t of the first yoke 4 to the first rotor surface 3A. The constant is the same as the number used to calculate the variation in thickness t, i.e., the number of first teeth 5. The variation in the thickness of the second yoke 6 is 2% or less of the average value of the distance between the second yoke surface 60 and the second rotor surface 3B. This average value is the average value of the linear distance extending in the perpendicular direction from the measurement position of the thickness t of the second yoke 6 to the second rotor surface 3B.

[0057] When current is applied, a circular magnetic path (see the two-dot chain line in FIG. 7) is formed that passes through the first core 10, the rotor 3, and the second core 20. The total height h of the first core 10 c The variation of the magnetic path length of the annular magnetic path is set to 1% or less. c The variation in the magnetic flux density is set to 1% or less of the magnetic path length of the annular magnetic path.

[0058] Here, the annular magnetic path in this example is a virtual annular magnetic path formed when current is applied to the coil (see the two-dot chain line in Figure 7). For example, an annular magnetic path is formed that passes through the first teeth 51, 54 of the U-phase and the second teeth 71, 74 of the U-phase. The annular magnetic path connects the first magnetic line, the second magnetic line, the third magnetic line, and the fourth magnetic line. The first magnetic line is a straight line that passes through the area centers of gravity of the end faces of the first teeth 51 and the second teeth 74 and penetrates the first teeth 51, the second teeth 74, and the rotor 3. The second magnetic line is a straight line that passes through the area centers of gravity of the end faces of the first teeth 54 and the second teeth 71 and penetrates the first teeth 54, the second teeth 71, and the rotor 3. The third magnetic line is a circular arc curve that lies on a plane that bisects the first yoke in the thickness direction and connects the first magnetic line and the second magnetic line. The fourth magnetic path is located on a plane that divides the second yoke in half in the thickness direction, and is an arc-shaped curve that connects the first magnetic path and the second magnetic path.

[0059] <Test example> In this test example, the influence of the combination of the first stator and the second stator on the torque and loss of the motor was determined by simulation. The following two samples were examined.

[0060] (Sample No. 1) The rotating electric machine of Sample No. 1 is a three-phase, 10-pole, 12-slot, double-stator type rotating electric machine. The first core and second core provided in this rotating electric machine each have 12 teeth. When the tooth with the highest protruding height is positioned at the 12 o'clock position, a first mark is provided between the tooth at the 12 o'clock position on the first core and the end of the yoke. Similarly, a second mark is provided between the tooth at the 12 o'clock position on the second core and the end of the yoke. The relationship between the protruding heights of the 12 teeth is as follows: Teeth at 12 o'clock > Teeth at 1 and 11 o'clock > Teeth at 2 and 10 o'clock > Teeth at 3 and 9 o'clock > Teeth at 4 and 8 o'clock > Teeth at 5 and 7 o'clock > Teeth at 6 o'clock

[0061] In sample No. 1, the first mark and the second mark were positioned symmetrically with respect to the rotation axis. That is, the first teeth at the 12 o'clock position of the first core faced the second teeth at the 6 o'clock position of the second core. In this configuration, the difference between the maximum inter-teeth distance L and the minimum inter-teeth distance L was 0.05 mm. Other requirements were as follows: Outer diameter of yoke: 56mm, inner diameter of yoke: 20mm Teeth cross-sectional area: 60mm 2 Coil turns: 43 turns Overall height h c Variation: 0.14mm Variation in yoke thickness: 0.05mm Teeth protrusion height h t Variation: 0.09mm Average distance between teeth and rotor surface: 1.0 mm Overall height h in the average distance between the teeth and the rotor surface cVariation percentage: 14% The percentage of variation in yoke thickness t in the average distance between the yoke surface and the rotor surface: 0.8% Overall height h relative to the magnetic path length c Variation rate: 0.2% Rotor speed: 2000 rpm ·Current density: 2.33Arms

[0062] (Sample No. 2) The rotating electric machine of Sample No. 2 is a double stator type rotating electric machine that uses the first core and second core used in Sample No. 1. However, the first mark and the second mark are positioned at the same position with respect to the rotation axis. In other words, the first teeth at the 12 o'clock position of the first core face the second teeth at the 12 o'clock position of the second core. In other words, this configuration gradually increases the distance between the teeth from the 12 o'clock position to the 6 o'clock position.

[0063] <Test Results> The torque ripple test results for sample No. 1 are shown in Fig. 8, and the cogging torque test results are shown in Fig. 9. In Figs. 8 and 9, the horizontal axis represents the rotor rotation angle (degrees), and the vertical axis represents torque (N m). As shown in Fig. 8, the average torque for sample No. 1 was 0.23 N m, and the torque ripple was 1.3% of the average torque. Furthermore, as shown in Fig. 9, the amplitude of the cogging torque for sample No. 1 was 0.00095 N m.

[0064] The energy efficiency of sample No. 1 was calculated. As a result, the electromagnetic energy efficiency of sample No. 1 was 66.2%, and the energy efficiency including mechanical losses was 66.0%. Energy efficiency is the ratio of the kinetic energy obtained from the motor to the electrical energy input to the motor.

[0065] Meanwhile, the torque ripple test results for sample No. 2 are shown in Figure 10, and the cogging torque test results are shown in Figure 11. Figures 10 and 11 can be interpreted in the same way as Figures 8 and 9. As shown in Figure 10, the average torque for sample No. 2 was 0.23 N·m, and the torque ripple was 2.7% of the average torque. Also, as shown in Figure 11, the cogging torque amplitude for sample No. 2 was 0.022 N·m. With the configuration of sample No. 2, there are areas where the inter-teeth distance is narrow and areas where it is wide at different positions around the rotor's circumference. With this configuration, there is significant variation in the torque provided by each tooth pair at various points around the rotor's circumference. Therefore, it is believed that the torque ripple and cogging torque of sample No. 2 are large.

[0066] The energy efficiency of sample No. 2 was calculated, and the electromagnetic energy efficiency of sample No. 2 was 66.2%, and the energy efficiency including mechanical loss was 59.3%.

[0067] The above results show that reducing the variation in the inter-tooth distance between each tooth pair reduces noise and vibration generated in the rotating electric machine. Also, reducing the variation in the inter-tooth distance between each tooth pair improves the energy efficiency of the rotating electric machine. [Explanation of symbols]

[0068] 100 Rotating electric machine, 101 Housing, 1 First stator, 10 First core, 11 First coil, 15 First mark, 2 Second stator, 20 Second core, 21 Second coil, 25 Second mark, 3 Rotor, 3A First rotor surface, 3B Second rotor surface, 30 Shaft, 31 Holding plate, 32 Magnet, 33 Bearing, 4 First yoke, 40 First yoke surface, 5, 51, 52, 53, 54, 55, 56 First teeth, 6 Second yoke, 60 Second yoke surface, 7, 71, 72, 73, 74, 75, 76 Second teeth, 8 Powder feeder, 8d Magnetic powder, 8s Powder feed axis 80 Powder feed port, 9 Mold, 90 Yoke forming section, 91, 92, 93, 94, 95, 96 Teeth forming section

Claims

1. An axial gap type rotating electric machine in which a first stator, a second stator, and a rotor are arranged in an axial direction of a rotation shaft of the rotor, the first stator includes a first coil and a first core made of a powder magnetic core on which the first coil is disposed, the second stator includes a second coil and a second core made of a powder magnetic core on which the second coil is disposed, The first core is a first yoke having a circular ring shape and a first yoke surface; a plurality of first teeth protruding from the first yoke surface, The second core is a second yoke having an annular shape and a second yoke surface facing the first yoke surface; a plurality of second teeth protruding from the second yoke surface, the first stator and the second stator are arranged such that the first teeth and the second teeth face each other, the first core and the second core have the same shape, When a first reference line passing through the axis of the first yoke is imaginary on the first yoke as viewed in the axial direction of the first yoke, and a second reference line passing through the axis of the second yoke is imaginary on the second yoke as viewed in the axial direction of the second yoke, the first reference line is a virtual line that is formed so that protruding heights of one tooth and another tooth that are positioned symmetrically with respect to the first reference line on the first core are the same, the second reference line is a virtual line that is formed so that protruding heights of one tooth and the other tooth that are positioned symmetrically with respect to the second reference line on the second core are the same, When viewed in the axial direction of the rotation shaft of the rotor, the first reference line and the second reference line coincide with each other, The highest tooth in the first core and the lowest tooth in the second core are arranged to face each other. Rotating electric motor.

2. a difference in protrusion height from the first yoke surface to end faces of the first teeth, the first teeth being symmetrical with respect to the first reference line, is 0.15 mm or less; 2. The rotating electric machine according to claim 1, wherein a difference in protrusion height from the second yoke surface to end faces of the second teeth located symmetrically with respect to the second reference line is 0.15 mm or less.

3. a plurality of tooth pairs each including the first tooth and the second tooth, the first tooth and the second tooth being positioned opposite each other in an axial direction of the rotation shaft; 3. A rotating electric motor as described in claim 1 or claim 2, wherein the distance between the teeth is the distance from the area center of gravity of the end face of the first tooth to the area center of gravity of the end face of the second tooth in each of the plurality of tooth pairs, and the difference between the maximum inter-teeth distance and the minimum inter-teeth distance is 0.08 mm or less.

4. a variation in overall height from a surface of the first core opposite to the first yoke surface to an end surface of the first tooth is 0.05 mm or more and 0.15 mm or less, A rotating electric motor as described in any one of claims 1 to 3, wherein the variation in overall height from the opposite surface of the second yoke surface to the end face of the second tooth for the plurality of second teeth in the second core is 0.05 mm or more and 0.15 mm or less.

5. The variation in thickness of the first yoke is 0.03 mm or more and 0.10 mm or less, 5. The rotating electric machine according to claim 1, wherein the second yoke has a thickness that varies from 0.03 mm to 0.10 mm.

6. The variation in the protruding height of the plurality of first teeth is 0.03 mm or more and 0.10 mm or less, The rotating electric machine according to claim 1 , wherein a variation in protruding height of the second teeth is equal to or greater than 0.03 mm and equal to or less than 0.10 mm.

7. the rotor includes a first rotor surface facing an end face of the first teeth and a second rotor surface facing an end face of the second teeth, a variation in overall height from a surface opposite to the first yoke surface to an end surface of the first teeth for the plurality of first teeth is 20% or less of an average value of a distance between the plurality of first teeth and the first rotor surface, A rotating electric motor as described in any one of claims 1 to 6, wherein the variation in the overall height from the opposite surface of the second yoke surface to the end face of the second teeth for the multiple second teeth is 20% or less of the average value of the distance between the multiple second teeth and the second rotor surface.

8. the rotor includes a first rotor surface facing an end face of the first teeth and a second rotor surface facing an end face of the second teeth, a variation in thickness of the first yoke is 2% or less of an average value of a distance between the first yoke surface and the first rotor surface; 8. The rotating electric machine according to claim 1, wherein a variation in thickness of the second yoke is 2% or less of an average value of a distance between the second yoke surface and the second rotor surface.

9. When energized, a ring-shaped magnetic path is formed that passes through the first core, the rotor, and the second core, a variation in overall height from a surface opposite to the first yoke surface to an end face of the first teeth in the plurality of first teeth is 1% or less of a magnetic path length of the annular magnetic path, 9. A rotating electric machine according to claim 1, wherein the variation in the overall height of the second teeth from the opposite surface of the second yoke surface to the end face of the second teeth is 1% or less of the magnetic path length of the annular magnetic path.

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