Rotor and rotating electric machine

Abstract

The present invention pertains to a rotor used in a rotating electric machine of an axial gap type, the rotor comprising: a disk-shaped support member into which a magnet is fitted; and a shaft having the rotational axis of the support member. The shaft comprises a main shaft part press-fitted into a first through-hole provided at the center of the support member, and a flange part provided at the outer periphery of the main shaft part. The flange part includes a seat surface facing a first surface of the support member. The seat surface includes an annular recessed portion that is provided so as to include a corner portion between the seat surface and an outer peripheral surface of the main shaft part. The recessed portion is not provided in the outer peripheral surface.

Description

Rotor and Rotating Electric Machine

[0001] The present disclosure relates to a rotor and a rotating electric machine. This application claims priority based on Japanese Patent Application No. 2025-004724 filed on January 14, 2025, and incorporates by reference all the descriptions set forth in the above-mentioned Japanese application.

[0002] Patent Document 1 discloses a rotor used in an axial-gap type rotating electric machine. The rotor includes a disc-shaped rotor body into which magnets are fitted. The rotor body is rotatable integrally with the shaft around the rotation axis of the shaft. The shaft includes a first shaft portion and a second shaft portion having a diameter larger than that of the first shaft portion. A through-hole is formed at the center of the rotor body, and the first shaft portion is press-fitted into this through-hole. The rotor body is positioned with respect to the shaft by being abutted against the end face of the second shaft portion. Hereinafter, the rotor body will be referred to as a support member. Also, among the shafts, the portion press-fitted into the through-hole is called the main shaft portion, and the portion having a surface against which the rotor body is abutted is called the flange portion.

[0003] International Publication No. 2022 / 270397

[0004] The rotor of the present disclosure is a rotor used in an axial-gap type rotating electric machine, and includes a disc-shaped support member into which magnets are fitted and a shaft having a rotation axis of the support member. The shaft includes a main shaft portion press-fitted into a first through-hole provided at the center of the support member and a flange portion provided on the outer periphery of the main shaft portion. The flange portion includes a seating surface facing the first surface of the support member. The seating surface includes an annular recess provided so as to include a corner portion between the outer peripheral surface of the main shaft portion and the seating surface. The recess is not provided on the outer peripheral surface.

[0005] FIG. 1 is a schematic perspective view showing the rotor of the embodiment. FIG. 2 is an exploded perspective view of the rotor of FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1. FIG. 4 is an enlarged view of a portion IV in FIG. 3. FIG. 5 is a schematic cross-sectional view showing an example of a rotating electric machine including the rotor of FIG. 1.

[0006] A rotor is desired in which, when the main shaft portion of the shaft is press-fitted into the through-hole of the support member, the thrust resistance and torsional resistance of the support member do not easily decrease relative to the shaft.

[0007] One of the objectives of this disclosure is to provide a rotor in which the thrust strength and torsional strength of the support member for the shaft are less likely to decrease.

[0008] The rotor of this disclosure is less prone to a decrease in the thrust strength and torsional strength of the support member relative to the shaft.

[0009] Generally, when the main shaft portion of a shaft is press-fitted into the through-hole of a support member, and the support member is then fitted against the seating surface of the flange portion, the corner between the outer surface of the main shaft portion and the seating surface of the flange portion is recessed. This recessing process creates a recess so that the aforementioned corner does not interfere with the corner between the first surface and the inner surface of the support member. The first surface is the surface of the support member that faces the seating surface. The inner surface is the surface of the support member that forms the through-hole into which the main shaft portion is press-fitted. Because the recess is formed, the aforementioned corner does not interfere with the corner, and the first surface of the support member comes into contact with the seating surface of the flange portion. When the first surface of the support member comes into contact with the seating surface of the flange portion, the support member is positioned relative to the shaft.

[0010] Considering the machining sequence, the recess is usually formed on the outer circumferential surface of the spindle portion, including the aforementioned corner. Specifically, in the case of a shaft with a flange, first, a round bar with a diameter larger than the flange portion is machined along the axis of the round bar from the first end of the round bar to the point where the flange portion is formed to form a part of the spindle portion, and then the seating surface of the flange portion is machined. Machining the seating surface of the flange portion is the last machining of the aforementioned corner. Therefore, the recess is formed on the outer circumferential surface of the spindle portion, including the aforementioned corner, when the machining tool strikes the outer circumferential surface of the spindle portion during machining of the seating surface.

[0011] When a recess is formed on the outer circumferential surface of the main shaft, the contact area between the outer circumferential surface of the main shaft and the inner circumferential surface of the support member becomes smaller compared to when no recess is formed on the outer circumferential surface of the main shaft. When the contact area between the outer circumferential surface of the main shaft and the inner circumferential surface of the support member becomes smaller, the thrust resistance and torsional resistance of the support member relative to the shaft decreases.

[0012] The inventors provided a recess on the seating surface of the flange portion, rather than on the outer circumferential surface of the main shaft portion. As a result of changing the position of the recess, it was found that the support member could be positioned relative to the shaft without the corner portion interfering with the corner portion of the support member, and that the thrust strength and torsional strength of the support member relative to the shaft were not easily reduced. Embodiments of this disclosure will be listed and described first.

[0013] (1) A rotor according to an embodiment of the present disclosure is a rotor used in an axial gap type rotating electric machine, comprising a disc-shaped support member into which magnets are fitted, and a shaft having a rotation axis of the support member. The shaft comprises a main shaft portion press-fitted into a first through hole provided in the center of the support member, and a flange portion provided on the outer circumference of the main shaft portion. The flange portion has a seating surface facing the first surface of the support member. The seating surface has an annular recess provided so as to include the corner between the outer circumference of the main shaft portion and the seating surface. The recess is not provided on the outer circumference.

[0014] Because a recess is provided that includes the corner between the outer circumferential surface of the main shaft and the seating surface of the flange, when the main shaft is press-fitted into the first through-hole of the support member, the corner between the first surface and the inner circumferential surface of the support member does not interfere with the corner between the outer circumferential surface of the main shaft and the seating surface of the flange. Therefore, when the main shaft is press-fitted into the first through-hole of the support member, the first surface of the support member contacts the seating surface of the flange. If the flange is provided at a location corresponding to the position where the support member is placed on the main shaft, the support member is positioned relative to the shaft by the contact of the first surface with the seating surface.

[0015] The recess is provided on the seating surface of the support member, but not on the outer circumferential surface of the main shaft. Therefore, the inner circumferential surface of the support member is in contact with the outer circumferential surface of the main shaft over its entire length. Because the inner circumferential surface of the support member is in contact with the outer circumferential surface of the main shaft over its entire length, the thrust strength and torsional strength of the support member relative to the shaft are less likely to decrease.

[0016] (2) In the rotor of (1) above, the opening width of the recess may be 0.1 times or more the thickness of the support member.

[0017] When the opening width of the recess is 0.1 times or more the thickness of the support member, the effect of providing the recess on the seating surface of the flange rather than the outer circumferential surface of the main shaft is significant. If the recess were provided on the outer circumferential surface of the main shaft, and the opening width of the recess was 0.1 times or more the thickness of the support member, the contact area between the outer circumferential surface of the main shaft and the inner circumferential surface of the support member would be 0.9 times or less the thickness of the support member. When the contact area between the outer circumferential surface of the main shaft and the inner circumferential surface of the support member is 0.9 times or less the thickness of the support member, the thrust strength and torsional strength of the support member relative to the shaft tend to decrease significantly. Because the recess is provided on the seating surface of the flange rather than the outer circumferential surface of the main shaft, the inner circumferential surface of the support member contacts the outer circumferential surface of the main shaft over its entire length, thus the thrust strength and torsional strength of the support member relative to the shaft are less likely to decrease.

[0018] (3) In the rotor of (1) or (2) above, the width of the seating surface may be 1.5 times or more the opening width of the recess.

[0019] If the width of the seating surface is 1.5 times or more the width of the recess opening, the contact area between the first surface of the support member and the seating surface of the flange is relatively large. Because the first surface of the support member and the seating surface of the flange are in contact over a certain area, the support member can be supported by the seating surface of the flange.

[0020] (4) In any of the rotors described in (1) to (3) above, the support member is provided with a second through hole opening to the first and second surfaces of the support member so as to be positioned for the magnet, and the seating surface may be in contact with a part of the magnet.

[0021] If the seating surface is large enough to make contact with a portion of the magnet, the contact area between the first surface of the support member and the seating surface of the flange becomes relatively large. When the seating surface is in contact with a portion of the magnet, the magnet can be supported by the seating surface, making it less likely for the magnet to fall out of the second through-hole.

[0022] (5) The rotor according to (4) above further comprises a first member that is attached to the main shaft so as to be in conjunction with the shaft, and a part of the magnet may be sandwiched between the seating surface and the first member.

[0023] The magnet, sandwiched between the seating surface and the first component, is firmly fixed within the second through-hole of the support member. Because the magnet is firmly fixed within the second through-hole, it is less likely to come off the support member even when the rotor is rotating at high speed, thereby improving the output of the rotating electric machine.

[0024] (6) In the rotor of (5) above, the first member may include a push nut that penetrates the main shaft portion.

[0025] The inner surface of the push nut is provided with angled claws. These claws bite into the outer surface of the main shaft when the push nut is fitted onto the main shaft. With a push nut, simply attaching it to the main shaft allows it to clamp a portion of the magnet together with the seating surface.

[0026] (7) A rotating electric machine according to an embodiment of the present disclosure comprises a rotor according to any of (1) to (6) above, and one or more stators.

[0027] In a rotating electric machine equipped with the above-mentioned rotor, the support member is positioned relative to the shaft, and the thrust resistance and torsional resistance of the support member relative to the shaft are less likely to decrease, thus improving the output of the rotating electric machine.

[0028] [Details of Embodiments of the Disclosure] Specific examples of rotors and rotating electric machines of the Disclosure will be described with reference to the drawings. Identical reference numerals in the drawings indicate the same or corresponding parts. In each drawing, some components may be exaggerated or simplified for illustrative purposes. The dimensional ratios of parts in the drawings may also differ from those of the actual components. The present invention is not limited to these examples, but is indicated by the claims, and all modifications within the meaning and scope of the claims are intended to be included. It should be understood that at least one configuration or feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways.

[0029] <Rotor> The rotor 1 of the embodiment will be described with reference to Figures 1 to 4, and Figure 5 as appropriate. The rotor 1 is used in an axial gap type rotating electric machine 8 shown in Figure 5. As shown in Figures 1 to 3, the rotor 1 comprises a support member 3 and a shaft 4. A first through hole 37 is provided in the center of the support member 3, and a magnet 2 is fitted around the first through hole 37. The shaft 4 comprises a main shaft portion 40 that is press-fitted into the first through hole 37, and a flange portion 42 provided on the outer circumference of the main shaft portion 40. As shown in Figure 3, the flange portion 42 has a seating surface 43 that faces the first surface 31 of the support member 3. The shaft 4 is provided with an annular recess 7 that includes the corner portion 45 between the outer circumferential surface 41 of the main shaft portion 40 and the seating surface 43. One of the features of the rotor 1 of Embodiment 1 is that, as shown in Figures 2 and 3, the recess 7 is provided on the seating surface 43 and not on the outer circumferential surface 41.

[0030] <Magnet> As shown in Figures 1 to 3, the magnet 2 is fitted into a second through-hole 38 provided in the support member 3. The magnet 2 is a flat plate-shaped member that can be placed inside the second through-hole 38. The magnet 2 has a shape that corresponds to the opening shape of the second through-hole 38. In this example, the opening shape of the second through-hole 38 is trapezoidal. The opening shape of the second through-hole 38 may also be fan-shaped. The magnet 2 is arranged around the rotation axis 5.

[0031] The rotor 1 in this example is equipped with multiple magnets 2. The multiple magnets 2 are arranged at equal intervals around the rotation axis 5. The number of magnets 2 is the same as the number of teeth 822, which are part of the core 82 of the stator 81 shown in Figure 5. The planar shape of each magnet 2 corresponds to the planar shape of the end face of each tooth 822. In this example, the planar shape of each magnet 2 is trapezoidal. The planar shape of each magnet 2 may also be fan-shaped. Each magnet 2 is magnetized in a direction parallel to the rotation axis 5. The magnetization directions of adjacent magnets 2 around the rotation axis 5 are opposite to each other. When the coil 83 of the stator 81 is excited and a rotating magnetic field is generated, the rotor 1 rotates relative to the stator 81 due to the attractive or repulsive force caused by the rotating magnetic field. When the rotor 1 rotates, the end faces of each tooth 822 receive magnetic flux from the rotating magnets 2.

[0032] The rotor 1 may be equipped with one magnet 2. If there is only one magnet 2, the shape of the magnet 2 is annular. In an annular magnet 2, the south pole and north pole are arranged alternately around the rotation axis 5.

[0033] As shown in Figures 2 and 3, the magnet 2 comprises a first surface 21, a second surface 22, an inner circumferential surface 23, and an outer circumferential surface 24. The first surface 21 and the second surface 22 are the front and back surfaces of the magnet 2. In this example, each of the first surface 21 and the second surface 22 faces the stator 81 shown in Figure 5. In this example, a part of the first surface 21 is in contact with the seat surface 43. In this example, a part of the second surface 22 is in contact with the first member 6. Details of the first member 6 will be described later. In this example, a part of the magnet 2 is sandwiched between the seat surface 43 and the first member 6. The inner circumferential surface 23 is the surface closer to the rotation axis 5. The outer circumferential surface 24 is the surface further from the rotation axis 5 than the inner circumferential surface 23.

[0034] As shown in Figure 3, the magnet 2 in this example has a first region 2A sandwiched between the seating surface 43 and the first member 6, and a second region 2B not sandwiched between the seating surface 43 and the first member 6. In Figure 3, the boundary between the first region 2A and the second region 2B is shown by a dashed line. In this example, the first region 2A is located near the rotation axis 5, and the second region 2B is located further from the rotation axis 5 than the first region 2A. The first region 2A does not have to be magnetized. If the first region 2A is not magnetized, it will be less likely to affect the magnetic circuit formed on the stator 81 even if the first member 6 is made of a magnetic material. The first region 2A may be magnetized.

[0035] In this example, the first surface 21 and the second surface 22 of the second region 2B are exposed. "Exposed" means that they do not have an artificially formed coating. An "artificially formed coating" is formed for the purpose of fixing the magnet 2 to the support member 3. This coating is, for example, a resin film that covers the magnet 2 and the support member 3 so that the magnet 2 fitted into the second through hole 38 becomes one with the support member 3. An "artificially formed coating" does not include natural oxide films or unavoidable surface contamination. When the first surface 21 and the second surface 22 of the second region 2B are exposed, it is easier to reduce the air gap between the end face of each tooth 822 and the magnet 2 as shown in Figure 5.

[0036] The thickness of the magnet 2 may be the same as the thickness 3T of the support member 3, or it may be greater than the thickness 3T. The thickness of the magnet 2 is the length parallel to the axis of rotation 5 between the first surface 21 and the second surface 22 of the magnet 2. The thickness 3T of the support member 3 is the length parallel to the axis of rotation 5 between the first surface 31 and the second surface 32 of the support member 3. In this example, the thickness of the magnet 2 is slightly greater than the thickness 3T of the support member 3, the first surface 21 is flush with the first surface 31 of the support member 3, and the second surface 22 protrudes slightly from the second surface 32 of the support member 3.

[0037] Magnet 2 is a permanent magnet. Specific examples of permanent magnets include ferrite magnets, neodymium magnets, samarium-cobalt magnets, or bonded magnets. Neodymium magnets and samarium-cobalt magnets, in particular, have strong magnetic forces.

[0038] <<Support Member>> As shown in Figure 1, the support member 3 is a disc-shaped member that supports the magnet 2. As shown in Figure 2, the support member 3 has a first through-hole 37 provided in the center of the support member 3. In this example, the opening shape of the first through-hole 37 is circular. As shown in Figure 3, the main shaft portion 40 of the shaft 4 is press-fitted into the first through-hole 37. The support member 3 and the shaft 4 are assembled by the main shaft portion 40 of the shaft 4 being press-fitted into the first through-hole 37. The support member 3 is rotatably supported by the shaft 4 in relation to the case 85 shown in Figure 5.

[0039] The support member 3 comprises a first surface 31, a second surface 32, an inner circumferential surface 33, and an outer circumferential surface 34. The first surface 31 and the second surface 32 are the front and back surfaces of the support member 3. Each of the first surface 31 and the second surface 32 faces the stator 81 shown in Figure 5. The support member 3 includes a second through hole 38 in which the magnet 2 is placed. The second through hole 38 opens to the first surface 31 and the second surface 32. In this example, the support member 3 comprises a plurality of second through holes 38 arranged at equal intervals around the first through hole 37. The annular region between the first through hole 37 and the plurality of second through holes 38 on the first surface 31 is in contact with the seat surface 43, as shown in Figure 3. In this example, the annular region between the first through hole 37 and the plurality of second through holes 38 on the second surface 32 is in contact with the first member 6, which will be described later. The inner circumferential surface 33 is the surface that forms the first through hole 37. The inner circumferential surface 33 is in contact with the outer circumferential surface 41 of the main shaft portion 40. The outer circumferential surface 34 is a surface that is further from the rotation axis 5 than the inner circumferential surface 33.

[0040] The thickness 3T of the support member 3 shown in Figure 4 is, for example, 1 mm to 20 mm. If the thickness 3T is 1 mm or more, the magnet 2 can be supported by the support member 3. If the thickness 3T is 20 mm or less, the support member 3 will not become too thick, making it easier to miniaturize the rotor 1. The thickness 3T of the support member 3 may also be 2 mm to 10 mm.

[0041] As shown in Figure 2, the support member 3 is provided with a frame-like portion to form a second through-hole 38. In this example, slits 39 are provided to divide the frame of this frame-like portion. The support member 3 in this example is provided with multiple slits 39. One slit 39 is provided for each second through-hole 38. In this example, the slits 39 are provided on the part of the frame-like portion that has an outer peripheral surface 34. Each slit 39 is provided to open into the first surface 31, the second surface 32, the outer peripheral surface 34, and the peripheral surface that forms the second through-hole 38. By dividing the frame-like portion with the slits 39, the eddy currents flowing through the frame-like portion are divided, and eddy current losses can be reduced.

[0042] The support member 3 is formed of, for example, stainless steel. The support member 3 formed of stainless steel has high strength. The support member 3 is formed of, for example, a non-magnetic material. If the support member 3 is formed of a non-magnetic material, the influence of the support member 3 on the magnetic circuit is small.

[0043] <<Shaft>> As shown in FIG. 1, the shaft 4 has a rotation shaft 5 of the rotor 1. The rotation shaft 5 is also the rotation shaft of the support member 3. As shown in FIGS. 2 and 3, the shaft 4 includes a main shaft portion 40 and a flange portion 42. The main shaft portion 40 is the main part of the shaft 4 and is press-fitted into the first through hole 37 of the support member 3. The main shaft portion 40 in this example is a round bar. The flange portion 42 is provided integrally with the main shaft portion 40.

[0044] The flange portion 42 is an annular plate-like member that protrudes in a direction along the diameter of the rotation shaft 5 from the main shaft portion 40. The seating surface 43 of the flange portion 42 is the surface facing the first surface 31 of the support member 3. The protruding length from the outer peripheral surface 41 of the main shaft portion 40 to the outer peripheral edge of the flange portion 42 can be appropriately selected within a range where the support member 3 can be supported by the seating surface 43. The seating surface 43 is in contact with an annular region between the first through hole 37 and the plurality of second through holes 38 on the first surface 31 of the support member 3. The seating surface 43 in this example is also in contact with a part of the first surface 21 of the magnet 2. By adjusting the above protruding length, the range of the first region 2A of the magnet 2 can be adjusted.

[0045] The thickness of the flange portion 42 can be appropriately selected according to the clearance of the air gap formed between the end surfaces of the respective teeth 822 shown in FIG. 5 and the magnet 2. The outer diameter of the flange portion 42 should be such that it does not interfere with the stator 81 shown in FIG. 5, particularly the coil 83.

[0046] As shown in FIG. 2, the seat surface 43 has an annular recess 7. As shown in FIGS. 3 and 4, the recess 7 is provided so as to include the corner 45 between the outer peripheral surface 41 of the main shaft portion 40 and the seat surface 43. The recess 7 is provided such that in a state where the main shaft portion 40 is press-fitted into the first through hole 37 of the support member 3, the corner 45 does not interfere with the corner 35 between the first surface 31 and the inner peripheral surface 33 of the support member 3. If the corner 45 interferes with the corner 35, in a state where the main shaft portion 40 is press-fitted into the first through hole 37 of the support member 3, the first surface 31 of the support member 3 contacts the seat surface 43. If the flange portion 42 is provided at a location corresponding to the position where the support member 3 is disposed on the main shaft portion 40, the support member 3 is positioned with respect to the shaft 4 when the first surface 31 contacts the seat surface 43.

[0047] The recess 7 is not provided on the outer peripheral surface 41 of the main shaft portion 40. Therefore, the inner peripheral surface 33 of the support member 3 is in contact with the outer peripheral surface 41 of the main shaft portion 40 over the entire area. Since the inner peripheral surface 33 is in contact with the outer peripheral surface 41 over the entire area, as shown in the test example described later, the thrust resistance and torsional resistance of the support member 3 with respect to the shaft 4 are less likely to decrease.

[0048] As shown in FIG. 4, the recess 7 is formed by locally recessing the seat surface 43. A part of the surface forming the recess 7 extends along the outer peripheral surface 41 of the main shaft portion 40. The cross-sectional shape of the recess 7 is, for example, triangular as shown in FIG. 4. A more specific cross-sectional shape of the recess 7 is a semi-groove shape. In this example, the inner surface of the recess 7 is inclined so as to move away from the first surface 31 of the support member 3 as it approaches the outer peripheral surface 41, and is inclined to the outer peripheral surface 41 so as to curve and approach the first surface 31 midway. The corner 45 formed by the outer peripheral surface 41 and the inclined seat surface 43 may be rounded or angular.

[0049] The opening width 7W of the recess 7 is, for example, 10% or more of the thickness 3T of the support member 3. The opening width 7W is the length of the recess 7 on the extended surface of the seating surface 43 other than the recess 7. When the opening width 7W is 10% or more of the thickness 3T, the effect of providing the recess 7 on the seating surface 43 of the flange portion 42 rather than the outer circumferential surface 41 of the main shaft portion 40 is significant. If the recess 7 were provided on the outer circumferential surface 41 of the main shaft portion 40, and the opening width of the recess 7 is 10% or more of the support member, the contact area between the outer circumferential surface 41 of the main shaft portion 40 and the inner circumferential surface 33 of the support member 3 would be 90% or less of the thickness 3T of the support member 3. When the recess 7 is provided on the outer circumferential surface 41 of the main shaft portion 40, the opening width of the recess 7 is the length of the recess 7 on the extended surface of the outer circumferential surface 41. If the contact area between the outer circumferential surface 41 and the inner circumferential surface 33 is 90% or less of the thickness 3T, the thrust strength and torsional strength of the support member 3 relative to the shaft 4 are likely to decrease significantly. Because the recess 7 is provided on the seating surface 43 of the flange portion 42 rather than the outer circumferential surface 41 of the main shaft portion 40, the inner circumferential surface 33 of the support member 3 is in contact with the outer circumferential surface 41 of the main shaft portion 40 over its entire area, so the thrust strength and torsional strength of the support member 3 relative to the shaft 4 are less likely to decrease.

[0050] The opening width 7W of the recess 7 may be 0.1 times or more, or 0.3 times or more, the thickness 3T of the support member 3. If the opening width 7W is too large, the contact area between the first surface 31 of the support member 3 and the seating surface 43 of the flange portion 42 will be small. Therefore, the opening width 7W is selected such that the width 43W of the seating surface 43 shown in Figure 3 is 1.5 times or more the opening width 7W. In other words, the width 43W of the seating surface 43 is, for example, 1.5 times or more the opening width 7W of the recess 7. The width 43W is the protruding length from the outer peripheral surface 41 of the main shaft portion 40 to the outer peripheral edge of the flange portion 42. If the width 43W is 1.5 times or more the opening width 7W, the contact area between the first surface 31 and the seating surface 43 is relatively large. Because the first surface 31 and the seating surface 43 are in contact over a certain area, the support member 3 can be stably supported by the seating surface 43 of the flange portion 42. The width 43W of the seat surface 43 may be more than twice the opening width 7W of the recess 7, or more than three times it. The upper limit of the width 43W of the seat surface 43 can be determined within the range in which the magnet 2 and the teeth 822 can rotate while facing each other.

[0051] The opening width 7W of the recess 7 is, for example, 1 mm or more and 50 mm or less. If the opening width 7W is 1 mm or more, the corner portion 45 is less likely to interfere with the corner portion 35. If the opening width 7W is 50 mm or less, although this depends on the width 43W of the seating surface 43, the contact area between the first surface 31 and the seating surface 43 is relatively large. The opening width 7W of the recess 7 may also be 2 mm or more and 20 mm or less.

[0052] The depth of the recess 7 is, for example, 0.1 mm or more and 3.0 mm or less. The depth of the recess 7 is the length from the extended surface of the seating surface 43 other than the recess 7 to the deepest point of the recess 7. If the depth of the recess 7 is 0.1 mm or more, the corner portion 45 is less likely to interfere with the corner portion 35. If the depth of the recess 7 is 3.0 mm or less, the mechanical strength of the flange portion 42 is less likely to decrease. The depth of the recess 7 may also be 0.2 mm or more and 1.0 mm or less.

[0053] In this example, the inclination angle θ of the seating surface 43 that forms the recess 7 (Figure 4) is between 5° and 60°. The inclination angle θ of the seating surface 43 that forms the recess 7 is the angle of the inclined surface extending from the seating surface 43 other than the recess 7 to the inner surface of the recess 7 with respect to the extended surface of the seating surface 43 other than the recess 7. If the inclination angle θ of the seating surface 43 that forms the recess 7 is 5° or more, the corner 45 is less likely to interfere with the corner 35. If the inclination angle θ of the seating surface 43 that forms the recess 7 is 60° or less, although this depends on the width 43W of the seating surface 43, the contact area between the first surface 31 and the seating surface 43 is relatively large. The inclination angle θ of the seating surface 43 that forms the recess 7 may also be between 10° and 45°.

[0054] The recess 7 can be formed, for example, as follows. First, a round bar having a diameter larger than the flange portion 42 is machined along the axis of the round bar from the first end of the round bar to the location where the flange portion 42 is formed to form a part of the main spindle portion 40. This machining is performed by moving the round bar, which rotates around its axis, and the cutting tool's blade relatively. The cutting tool is, for example, a cutting tool. When machining the main spindle portion 40, the area near the location where the flange portion 42 is formed on the main spindle portion 40 may be roughly machined. Next, the seating surface 43 of the flange portion 42 is machined. The machining of the seating surface 43 is also done by cutting with, for example, a cutting tool. When machining the seating surface 43, the machining tool is not applied to the outer circumferential surface 41 so as not to form a recess on the outer circumferential surface 41 of the main spindle portion 40. After that, the area near the location where the flange portion 42 is formed on the main spindle portion 40 is finished. At this time, by applying the machining tool to the seating surface 43, the recess 7 can be formed on the seating surface 43 so as to include the corner portion 45. After machining the seating surface 43, the outer circumferential surface of the flange portion 42, the surface opposite to the seating surface 43, and the remaining portion of the main shaft portion 40 are machined in order.

[0055] The shaft 4 is made of, for example, carbon steel. A shaft 4 made of carbon steel has high strength. A shaft 4 made of carbon steel has excellent workability. The shaft 4 may be made of a non-magnetic material or a magnetic material. If the shaft 4 is made of a non-magnetic material, that is, if the flange portion 42 is made of a non-magnetic material, the influence of the flange portion 42 on the magnetic circuit is small, even if the first region 2A of the magnet 2 is magnetized. If the shaft 4 is made of a magnetic material, that is, if the flange portion 42 is made of a magnetic material, a magnetic attractive force acts between the magnet 2 and the flange portion 42, which can improve the fixing strength of the magnet 2.

[0056] <<First Component>> As shown in Figures 1 to 3, the rotor 1 in this example further includes a first component 6 that is mounted on the main shaft portion 40 in conjunction with the shaft 4. The first component 6 is independent of the shaft 4 and is a component that can be mounted on the main shaft portion 40. The first component 6 mounted on the shaft 4 rotates in conjunction with the shaft 4. In other words, the first component 6 mounted on the shaft 4 rotates in conjunction with the shaft 4 together with the support member 3 on which the magnet 2 is arranged.

[0057] The first component 6 in this example includes a push nut 61 and a buffer member 62 that pass through the main shaft portion 40. The push nut 61 has an annular base portion and a claw portion that extends from the base portion toward the center of the push nut 61. The main shaft portion 40 passes through a through hole provided in the center of the base portion. The base portion has an annular region between the first through hole 37 and a plurality of second through holes 38 on the second surface 32 of the support member 3, and a surface facing a part of the second surface 22 of the magnet 2. The width of the base portion can be appropriately selected within a range in which the base portion can face a part of the second surface 22. The width of the base portion is the length between the inner circumferential surface and the outer circumferential surface of the base portion. The claw portion is inclined away from the base portion as it moves toward the center of the push nut 61 from the base portion. When the push nut 61 is attached to the main shaft portion 40, the claw portion is fitted to the main shaft portion 40 such that the inner circumferential edge of the claw portion moves away from the support member 3 as it moves toward the center of the push nut 61. When the push nut 61 is attached to the main shaft portion 40, the inner periphery of the claw portion bites into the outer circumferential surface 41 of the main shaft portion 40. This biting of the claw portion fixes the push nut 61 to the main shaft portion 40.

[0058] The push nut 61 is made of, for example, stainless steel. A push nut 61 made of stainless steel has high strength. The push nut 61 is made of, for example, a non-magnetic material. If the push nut 61 is made of a non-magnetic material, the influence of the push nut 61 on the magnetic circuit is small.

[0059] The buffer member 62 is positioned between the support member 3, into which the magnet 2 is fitted, and the push nut 61. In this example, a step is formed between the second surface 22 of the magnet 2 and the second surface 32 of the support member 3, and this step is absorbed by the buffer member 62. Because the step is absorbed by the buffer member 62, the surface pressure from the push nut 61 tends to become uniform. When the buffer member 62 is positioned between the push nut 61 and the magnet 2, damage to the magnet 2 caused by the pressure of the push nut 61 is less likely to occur. For example, a commercially available gasket can be used as the buffer member 62. The buffer member 62 is not essential. If the first member 6 does not have a buffer member 62, for example, the second surface 22 of the magnet 2 and the second surface 32 of the support member 3 are flush. If the first member 6 does not have a buffer member 62 and the above-mentioned step is formed, for example, a protrusion that can absorb the above-mentioned step may be formed on the push nut 61. This protrusion is provided, for example, on the surface of the base portion of the push nut 61 that faces the support member 3.

[0060] The buffer member 62 can press down on the magnet 2 and the support member 3 together with the push nut 61 and is made of a material that has cushioning properties. The buffer member 62 is made of, for example, a non-magnetic material. If the buffer member 62 is made of a non-magnetic material, the influence of the buffer member 62 on the magnetic circuit will be small. The buffer member 62 is made of, for example, a carbon material.

[0061] In this example, the outer diameters of the push nut 61 and cushioning member 62 when mounted on the main shaft portion 40 of the shaft 4 are larger than the outer diameter of the flange portion 42 of the shaft 4. The outer diameters of the push nut 61 and cushioning member 62 when mounted on the main shaft portion 40 of the shaft 4 may be the same as or smaller than the outer diameter of the flange portion 42.

[0062] In this example, a portion of the magnet 2 is sandwiched between the seating surface 43 of the flange portion 42 and the first member 6. The magnet 2 sandwiched between the seating surface 43 and the first member 6 is firmly fixed within the second through-hole 38 of the support member 3. Because the magnet 2 is firmly fixed within the second through-hole 38, the magnet 2 is less likely to come off the support member 3 even when the rotor 1 is rotated at high speed, and the output of the rotating electric machine 8 shown in Figure 5 can be improved. When the magnet 2 is sandwiched between the seating surface 43 and the first member 6, a heat transfer path is formed from the first surface 21 of the magnet 2 through the seating surface 43 toward the main shaft portion 40. In addition, a heat transfer path is formed from the second surface 22 of the magnet 2 through the first member 6 toward the main shaft portion 40. The rotor 1 having the above heat transfer paths has excellent heat dissipation properties.

[0063] Although not shown in the diagram, the magnet 2 may be fixed in the second through-hole 38 with adhesive. The adhesive is provided between the circumferential surface forming the second through-hole 38 and the outer circumferential surface 24 of the magnet 2. When the magnet 2 and the support member 3 are fixed with adhesive, the magnet 2 is firmly fixed in the second through-hole 38. Depending on the heat resistance of the adhesive or the operating environment of the rotor 1, the adhesive may soften. If the magnet 2 is sandwiched between the seating surface 43 and the first member 6, even if the adhesive softens, the magnet 2 will not easily come off the support member 3.

[0064] Although not shown in the diagram, the first member 6 may be a retaining member with a screw instead of a push nut 61. The retaining member with a screw is, for example, a member equipped with a nut having a female thread, specifically a flange nut. In this case, the outer circumferential surface 41 of the main shaft portion 40 is provided with a male thread. This male thread is screw-connected to the female thread.

[0065] <Rotating Electric Machine> The rotating electric machine 8 of the embodiment will be described with reference to Figure 5. Figure 5 is a cross-sectional view of the rotating electric machine 8 cut by a plane parallel to the rotation axis 5. The rotating electric machine 8 can be used as a motor or a generator. The rotating electric machine 8 comprises the rotor 1 of the embodiment described above and one or more stators 81. The rotating electric machine 8 shown in Figure 5 is a single-rotor, double-stator type comprising one rotor 1 and two stators 81. In the single-rotor, double-stator type rotating electric machine 8, the support member 3 into which the magnet 2 is fitted is assembled so as to be sandwiched between the two stators 81 along the rotation axis 5 of the shaft 4.

[0066] In addition, the rotating electric machine may be a single-rotor, single-stator type comprising one rotor 1 and one stator 81, or a double-rotor, single-stator type comprising two rotors 1 and one stator 81. In the double-rotor, single-stator type rotating electric machine, one stator 81 is assembled so as to be sandwiched between two assemblies, each consisting of a support member 3 into which a magnet 2 is fitted, along the rotation axis 5.

[0067] Each stator 81 comprises a core 82 and a coil 83. The core 82 comprises a yoke 821 and a plurality of teeth 822. The yoke 821 is an annular plate shape. A through hole is provided in the center of the yoke 821. A bearing (not shown) is provided in this through hole, and the main shaft portion 40 of the shaft 4 is inserted through this bearing. The plurality of teeth 822 are arranged at equal intervals around the rotation axis 5. Each tooth 822 is columnar in shape. Each tooth 822 protrudes from the first or second surface, which is the front or back surface of the yoke 821. The end face of each tooth 822 faces the magnet 2. The yoke 821 magnetically couples adjacent teeth 822 among the plurality of teeth 822 arranged around the rotation axis 5. The yoke 821 and each tooth 822 are, for example, a single compacted powder molded body. The coil 83 is arranged on each tooth 822. The coil 83 has a cylindrical portion formed by winding a wire in a spiral shape. The coil 83 is, for example, a rectangular cylindrical edgewise wound coil with a covered flat wire for the winding.

[0068] The rotor 1 and stator 81 are housed in a case 85 having a cylindrical internal space. The case 85 comprises a cylindrical section and two plate sections. The cylindrical section surrounds the outer circumference of the rotor 1 and stator 81. Plate sections are located at both ends of the cylindrical section. The rotor 1 and stator 81 are housed in the case 85 so as to be sandwiched between the two plate sections. The stator 81 is fixed to the case 85 by a part of the yoke 821 being fitted into the plate section. A through hole is provided in the center of the plate section. A bearing (not shown) is provided in this through hole, and the main shaft section 40 of the shaft 4 is inserted through this bearing. The main shaft section 40 penetrates the inside of the case 85.

[0069] In the rotating electric machine 8 equipped with the rotor 1 of this embodiment, the support member 3 is positioned relative to the shaft 4, and the thrust strength and torsional strength of the support member 3 relative to the shaft 4 do not easily decrease, thus improving the output of the rotating electric machine 8. In this example, a part of the magnet 2 is sandwiched between the seating surface 43 of the flange portion 42 and the first member 6, and even when the rotor 1 is rotated at high speed, the magnet 2 does not easily come off the support member 3, thus improving the output of the rotating electric machine 8. In addition, in this example, a part of the magnet 2 is sandwiched between the seating surface 43 of the flange portion 42 and the first member 6, and a heat transfer path is formed from the magnet 2 toward the main shaft portion 40, so the rotor 1 has excellent heat dissipation. When the rotor 1 has excellent heat dissipation, heat does not easily accumulate around the coil 83, and as a result the stator 81 also has excellent heat dissipation. When the rotor 1 and stator 81 each have excellent heat dissipation, heat does not easily accumulate inside the case 85, and the entire rotating electric machine 8 has excellent heat dissipation.

[0070] [Test Example] In the test example, for test specimens A and B, which differ in the position of the recesses formed at the corners between the outer circumferential surface of the main shaft portion and the seating surface of the flange portion, the thrust strength and torsional strength of the support member relative to the shaft were calculated using analysis software when the main shaft portion was pressed into the support member.

[0071] <Description of Test Specimens> Test specimens A and B differ in the position of the recesses formed in the corners, but all other conditions are the same. In both test specimens A and B, the support members are made of SUS304 stainless steel. The thickness of the support members is 3.5 mm. A first through hole is formed in the center of the support member, into which the main shaft is press-fitted. In both test specimens A and B, the shafts are made of S45C carbon steel for machine structural use. The outer diameter of the shafts is 20 mm. The width of the seating surface facing the support member at the flange portion is 8 mm.

[0072] The recess in test specimen A is located on the seating surface of the flange portion, but not on the outer circumferential surface of the main shaft portion. The opening width of the recess is 1.06 mm, which is approximately 0.3 times the thickness of the support member. The opening width of the recess in test specimen A is the length of the recess on the extended surface of the seating surface other than the recess. The depth of the recess is 0.3 mm. The depth of the recess in test specimen A is the length from the extended surface of the seating surface other than the recess to the deepest point of the recess. The width of the seating surface is approximately 7.5 times the opening width of the recess.

[0073] The recess in test specimen B is located on the outer circumferential surface of the main shaft portion, but not on the seating surface of the flange portion. The opening width of the recess is 1.06 mm, which is approximately 0.3 times the thickness of the support member. The opening width of the recess in test specimen B is the length of the recess on the extended surface of the outer circumferential surface. The depth of the recess is 0.3 mm. The depth of the recess in test specimen B is the length from the extended surface of the outer circumferential surface to the deepest point of the recess.

[0074] The main shaft portion was press-fitted into the first through-hole of the support member. The fit tolerance between the first through-hole and the main shaft portion was set to 45 μm.

[0075] In both test specimen A and test specimen B, with the main shaft pressed into the first through hole, the corner of the support member did not interfere with the corner between the outer surface of the main shaft and the seating surface of the support member. Therefore, in both test specimen A and test specimen B, the surface of the support member facing the seating surface was in surface contact with the seating surface.

[0076] For test specimens A and B, a load was applied from above the support member to the overlapping area between the support member and the flange portion. The thrust force when the support member slid in the direction along the axis of rotation was calculated, and this value was defined as the thrust strength. As a result, the thrust strength of test specimen A was approximately 37% greater than that of test specimen B.

[0077] For test specimens A and B, with the main shaft fixed, a load was applied to the flange portion around the axis of rotation, and the torsional force when the support member slid around the axis of rotation was calculated and defined as the torsional strength. As a result, the torsional strength of test specimen A was approximately 37% greater than that of test specimen B.

[0078] The results above indicate that the recess being located on the seating surface of the flange rather than the outer circumferential surface of the main shaft prevents a decrease in the thrust and torsional strength of the support member relative to the shaft. When the recess is located on the seating surface of the flange rather than the outer circumferential surface of the main shaft, the inner circumferential surface of the support member contacts the outer circumferential surface of the main shaft over its entire length. It is thought that this contact between the inner circumferential surface of the support member and the outer circumferential surface of the main shaft over its entire length prevents a decrease in the thrust and torsional strength of the support member relative to the shaft.

[0079] 1 Rotor 2 Magnet 21 First surface, 22 Second surface, 23 Inner surface, 24 Outer surface 2A First region, 2B Second region 3 Support member 31 First surface, 32 Second surface, 33 Inner surface, 34 Outer surface 35 Corner 37 First through hole, 38 Second through hole 39 Slit 3T Thickness 4 Shaft 40 Main shaft portion, 41 Outer surface 42 Flange portion, 43 Seat surface, 43W Width 45 Corner 5 Rotating shaft 6 First member, 61 Push nut, 62 Cushioning member 7 Recess, 7W Opening width, θ Inclination angle 8 Rotating electric machine 81 Stator, 82 Core, 821 Yoke, 822 Teeth 83 Coil, 85 Case

Claims

1. A rotor for use in an axial gap type rotating electric machine, comprising: a disc-shaped support member into which magnets are fitted; and a shaft having a rotation axis of the support member, wherein the shaft comprises: a main shaft portion press-fitted into a first through hole provided in the center of the support member; and a flange portion provided on the outer circumference of the main shaft portion, wherein the flange portion has a seating surface facing the first surface of the support member; the seating surface has an annular recess provided so as to include the corner between the outer circumference of the main shaft portion and the seating surface; the recess is not provided on the outer circumference.

2. The rotor according to claim 1, wherein the opening width of the recess is 0.1 times or more the thickness of the support member.

3. The rotor according to claim 1 or claim 2, wherein the width of the seat surface is 1.5 times or more the opening width of the recess.

4. The rotor according to any one of claims 1 to 3, wherein the support member has a second through hole opening to the first and second surfaces of the support member so as to be positioned for the magnet, and the seat surface is in contact with a portion of the magnet.

5. The rotor according to claim 4, further comprising a first member mounted on the main shaft portion in conjunction with the shaft, wherein a portion of the magnet is sandwiched between the seating surface and the first member.

6. The rotor according to claim 5, wherein the first member includes a push nut that penetrates the main shaft portion.

7. A rotating electric machine comprising a rotor according to any one of claims 1 to 6, and one or more stators.

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