Rotor member, rotor, and motor

Abstract

A rotor member for a motor includes a shaft part, and a rotor core part that is formed of ceramic and has a through hole into which the shaft part is inserted, and a support part for supporting a magnet.

Description

Rotor member, rotor, and motor

[0001] The present invention relates to a rotor member, a rotor, and a motor.

[0002] 2. Description of the Related Art Rotor members for motors have been known in the past (see, for example, Patent Documents 1 and 2).

[0003] JP 2016-40996 A International Publication No. 2018 / 147052

[0004] However, even with the prior art such as Patent Documents 1 and 2, there is still room for improvement in the technology for efficiently rotating rotor members for motors.

[0005] An object of the present invention is to provide a technique for efficiently rotating a rotor member for a motor.

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a rotor member for a motor, the rotor member including a rotor core made of ceramic, the rotor core having a shaft portion, a through hole into which the shaft portion is inserted, and a support portion for supporting a magnet.

[0008] According to this configuration, the rotor core, which has a through hole into which the shaft is inserted, rotates outside the shaft when the shaft rotates in the motor. Because the rotor core is made of relatively lightweight ceramic, the input force required to rotate the rotor member can be made relatively small. Furthermore, because the rotor core is made of ceramic, iron loss is reduced. This reduces input loss compared to when the rotor core is made of electromagnetic steel sheet. Therefore, the rotor member can be rotated efficiently.

[0009] (2) The rotor member of the above embodiment includes a joint portion that joins the shaft portion and the rotor core portion, and the joint strength between the shaft portion and the rotor core portion by the joint portion is 200 N or more, and the absolute value of the difference between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion is 3×10 －６ / K or less. According to this configuration, the rotor member has the shaft portion and the rotor core portion joined by a joint having a joining strength of 200 N or more. Furthermore, the absolute value of the difference between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion may be 3×10 －６ / K or less, the dimensional relationship between the shaft portion and the rotor core portion is unlikely to change even if the temperature of the rotor member rises. This allows the shaft portion and the rotor core portion to be maintained in a joined state by the joint. Therefore, damage due to torsional stress generated when the rotor member rotates can be suppressed.

[0010] (3) In the rotor member of the above aspect, the through hole may have an inner diameter that decreases from one opening to the other. With this configuration, the shaft portion inserted into the through hole, whose inner diameter decreases from one opening to the other, contacts the inner wall of the through hole and is securely fixed to the rotor core portion by friction with the rotor core portion. This makes it difficult for the shaft portion to come out of the through hole, thereby suppressing damage due to torsional stress that occurs when the rotor member rotates.

[0011] (4) According to another aspect of the present invention, a rotor for a motor is provided. This rotor includes the rotor member described above, a magnet supported by the support portion, and a magnetic portion provided in the rotor core portion and formed of metal or soft magnetic ceramic, the magnet forming a magnetic circuit passing through the magnetic portion. According to this configuration, the rotor core portion is provided with a magnetic portion through which the magnetic circuit formed by the magnet passes. The rotor member provided in the rotor core portion formed of ceramic has relatively small iron loss and mechanical loss, and therefore is less likely to increase in temperature. This suppresses the temperature increase in the magnetic portion provided in the rotor core portion, thereby suppressing performance degradation of the magnetic portion.

[0012] (5) According to yet another aspect of the present invention, there is provided a motor. The motor includes the rotor member described above, a magnet supported by the support, and a stator for the motor, disposed outside the rotor core and having windings for generating a magnetic field. With this configuration, the motor includes a rotor member having a rotor core made of ceramic, so that iron loss and mechanical loss in the rotor are relatively small. This suppresses temperature rise in the rotor, thereby suppressing temperature rise in the entire motor.

[0013] The present invention can be realized in various forms, for example, in the form of an apparatus that uses a rotor member, a method for manufacturing a rotor member, a method for manufacturing a rotor or motor that includes a rotor member, or a computer program that causes a computer to manufacture a rotor member.

[0014] 11 is a cross-sectional view of a motor including a rotor member of the first embodiment. FIG. 12 is a perspective view of the rotor member of the first embodiment. FIG. 13 is a cross-sectional view of the rotor member of the first embodiment. FIG. 14 is an enlarged view of part A in FIG. 3. FIG. 15 is a perspective view of the rotor of the first embodiment. FIG. 16 is a cross-sectional view of the rotor of the first embodiment. FIG. 17 is a diagram explaining evaluation results for the rotor member of the first embodiment. FIG. 18 is a cross-sectional view of a rotor of a comparative example. FIG. 19 is a cross-sectional view of a motor including a rotor member of the second embodiment. FIG. 19 is a perspective view of the rotor member of the second embodiment. FIG. 19 is a cross-sectional view of the rotor member of the second embodiment. FIG. 19 is an enlarged view of part B in FIG. 11. FIG. 19 is a perspective view of the rotor of the second embodiment. FIG. 19 is a cross-sectional view of the rotor of the second embodiment. FIG. 20 is a diagram explaining a magnetic circuit formed in the rotor of the second embodiment. FIG. 21 is a diagram explaining evaluation results for the rotor member of the second embodiment. FIG. 22 is a cross-sectional view of the rotor of the comparative example.

[0015] <First embodiment> Fig. 1 is a cross-sectional view of a motor including a rotor member according to a first embodiment. A rotor member 100 according to this embodiment is used in a motor 1 that outputs rotational torque when supplied with electric power. The motor 1 includes a rotor 10, a stator 20, and a motor case 30. The rotor 10 is provided on a central axis C1 of the motor 1 so as to be rotatable about the central axis C1. The rotor 10 includes the rotor member 100 and a magnet 140.

[0016] Fig. 2 is a perspective view of the rotor member of this embodiment. Fig. 3 is a cross-sectional view of the rotor member of this embodiment, including the central axis C100 of the rotor member 100. The rotor member 100 includes a rotor core portion 120 formed of ceramic and having a shaft portion 110, a through hole 121 into which the shaft portion 110 is inserted, and a support portion 122 for supporting a magnet 140, and a joint portion 130 that joins the shaft portion 110 and the rotor core portion 120. The rotor member 100 of this embodiment is formed by joining the shaft portion 110 and the rotor core portion 120, which are formed from separate members, via the joint portion 130.

[0017] As shown in Fig. 3 , the shaft portion 110 is a substantially rod-shaped member. In the rotor member 100, the shaft portion 110 is disposed such that its longitudinal direction is along the central axis C100 of the rotor member 100. Two end portions 111, 112 of the shaft portion 110 both protrude from the rotor core portion 120 and are exposed to the outside of the motor case 30, which will be described later, as shown in Fig. 1 . As shown in Fig. 3 , of the two end portions 111, 112 of the shaft portion 110, the end with the longer portion protruding from the rotor core portion 120 is referred to as the load side end portion 111, and the end with the shorter portion protruding from the rotor core portion 120 is referred to as the anti-load side end portion 112.

[0018] As shown in FIG. 2 , the rotor core portion 120 has a generally cylindrical shape. The through hole 121 into which the shaft portion 110 is inserted is formed along the central axis C100 of the rotor member 100. The through hole 121 is formed such that the inner diameter changes between one opening 121a formed in one end face 123 of the two end faces 123, 124 of the generally cylindrical rotor core portion 120 and the other opening 121b formed in the other end face 124 (see FIG. 3 ). Specifically, the inner diameter Ra of the one opening 121a is larger than the inner diameter Rb of the other opening 121b. In this embodiment, the through hole 121 is formed such that the inner diameter decreases from the one opening 121a toward the other opening 121b. As a result, when the shaft portion 110 is inserted into the through-hole 121 from one of the openings 121 a, the shaft portion 110 is fixed to the rotor core portion 120 also by the frictional force between the outer wall of the shaft portion 110 and the inner wall of the through-hole 121 .

[0019] The support portions 122 are recessed portions formed on a side surface 125 of the rotor core portion 120, which has a substantially cylindrical shape. In this embodiment, four support portions 122 are formed on the side surface 125 of the rotor core portion 120, lined up along the circumferential direction of the rotor core portion 120.

[0020] In this embodiment, the shaft portion 110 is made of a nickel alloy (thermal expansion coefficient: 9.2×10 －６ The rotor core 120 of this embodiment is made of alumina (Al ２ O ３ ) and zirconia (ZrO ２ ) (thermal expansion coefficient: 9.2 × 10 －６ / K). In this embodiment, the absolute value of the difference between the thermal expansion coefficient of the shaft portion 110 and the thermal expansion coefficient of the rotor core portion 120 is 0 / K or more and 3×10 －６ / K or less, i.e., 0 / K. The thermal expansion coefficients of the shaft portion 110 and the rotor core portion 120 are measured using a thermomechanical analyzer (TMA) (measurement sample size: 3 mm x 3 mm x 10 mm). The material forming the rotor core portion 120 is identified using X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). The material forming the shaft portion 110 is not limited to nickel alloy, but may be other alloys such as iron alloys and titanium alloys, or ceramics. The material forming the rotor core portion 120 is preferably at least one of oxides, carbides, and nitrides among ceramics.

[0021] The joint portion 130 joins the shaft portion 110 and the rotor core portion 120. In this embodiment, the joint portion 130 is a brazed solder.

[0022] FIG. 4 is an enlarged view of portion A in FIG. 3 . The distance between the shaft portion 110 and the rotor core portion 120 at the through hole 121 is greater at the load side end 111 of the shaft portion 110 than at the anti-load side end 112 of the shaft portion 110. Specifically, as shown in FIG. 4 , the distance Ga on the load side end 111 side is greater than the distance Gb on the anti-load side end 112 side. The solder, which is the joint portion 130, joins the shaft portion 110 and the rotor core portion 120 by entering between the shaft portion 110 and the rotor core portion 120 in the through hole 121. In this embodiment, the joint strength between the shaft portion 110 and the rotor core portion 120 by the joint portion 130 is 200 N or more and 500 N or less. Note that the method of joining the shaft portion 110 and the rotor core portion 120 is not limited to this.

[0023] Fig. 5 is a perspective view of the rotor of this embodiment. Fig. 6 is a cross-sectional view of the rotor of this embodiment. The magnet 140 is supported by the rotor core portion 120 by being fitted into the support portion 122 of the rotor core portion 120, i.e., into a recessed portion formed in the side surface 125 of the rotor core portion 120. In other words, the motor 1 of this embodiment is a so-called SPM motor in which the magnet 140 is mounted on the surface of the rotor core portion 120. Note that the magnet 140 may be fixed to the recessed portion of the support portion 122 with an adhesive (resin), or may be fixed (for example, welded) directly to the rotor core portion 120 without using an adhesive.

[0024] The stator 20 has a stator core portion 210 and a winding 220 (see FIG. 1). The stator 20 is disposed outside the rotor core portion 120 and is fixed to the motor case 30 (described later) inside the motor case 30. The stator core portion 210 is formed to have a substantially cylindrical shape and has a plurality of protrusions 211 on the inside. The stator core portion 210 is formed by stacking a plurality of electromagnetic steel plates.

[0025] The windings 220 are conductor wires covered with an insulator, and are wound around each of the plurality of protrusions 211 of the stator core 210. When electricity supplied from outside the motor 1 flows through the windings 220, the windings 220 generate a magnetic field.

[0026] The motor case 30 is a hollow member that houses the rotor 10 and the stator 20. Two bearings 310, 320 are provided in the motor case 30. The bearings 310, 320 are provided on two opposing bracket portions 301, 302 of the motor case 30, respectively. One end of the shaft portion 110 is inserted into the bearing 310, and the other end of the shaft portion 110 is inserted into the bearing 320. In this way, the rotor 10 is rotatably supported by the motor case 30.

[0027] Next, an example of a manufacturing method for the rotor member 100 of this embodiment will be described. In the manufacturing method for the rotor member 100, first, predetermined amounts of ceramic particles and sintering aid are weighed as main raw materials. In this embodiment, columnar ceramic particles are added when weighing the ceramic particles. Next, the weighed materials are charged into a ball mill together with ethanol, and pulverized and mixed for a predetermined time to prepare a slurry. Next, the prepared slurry is extrusion-molded to form an extrusion-molded body having the general shape of the rotor core portion 120. Next, portions that will become the through holes 121, the support portions 122, and the like are machined into the extrusion-molded body to prepare a processed molded body having the shape of the rotor core portion 120. Next, the processed molded body is fired by heating under predetermined conditions to prepare the rotor core portion 120. Meanwhile, a rod-shaped member formed of a nickel alloy is machined to prepare the shaft portion 110. Finally, the shaft portion 110 is inserted into the through hole 121 of the rotor core portion 120, and the shaft portion 110 and the rotor core portion 120 are brazed together to produce the rotor member 100. In a method of joining the shaft portion 110 and the rotor core portion 120, after the shaft portion 110 is inserted into the through hole 121, ceramic wool may be press-fitted into the gap between the shaft portion 110 and the rotor core portion 120 in the through hole 121. Note that the manufacturing method of the rotor member 100 shown here is an example, and is not limited to this manufacturing method.

[0028] Next, an evaluation test of the rotor member according to this embodiment will be described. In this evaluation test, 11 types of rotor members (hereinafter referred to as "samples") for use in SPM motors were fabricated, differing in the material of the rotor core portion, the thermal expansion coefficient of the rotor core portion, the material of the shaft portion, the thermal expansion coefficient of the shaft portion, the difference in the thermal expansion coefficient, the joining method, the joining strength, and the presence or absence or material of a magnetic portion, and the "rotational strength," "iron loss," and "rotational efficiency" were evaluated for each of the 11 samples.

[0029] FIG. 7 is a diagram illustrating the evaluation results of the rotor member. Of the 11 types of samples used in this evaluation test, Samples 1 to 10 were manufactured by a method conforming to the manufacturing method of the rotor member 100 of this embodiment. For each of Samples 1 to 10, materials were selected so that the shaft portion and rotor core portion each had the composition of the "material" shown in FIG. 7. Sample 11 was manufactured by joining a shaft portion made of an aluminum alloy and a rotor core portion made of epoxy resin by wool press-fitting. Note that ZrB ２ and Al ２ O ３ and the volume ratio of Al in Samples 8 to 10. ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0030] The "thermal expansion coefficient" shown in Figure 7 indicates the thermal expansion coefficient of the "material" forming each of Samples 1 to 11. The "thermal expansion coefficient difference" shown in Figure 7 indicates the absolute value of the difference between the thermal expansion coefficient of the material forming the shaft portion and the thermal expansion coefficient of the material forming the rotor core portion for each of Samples 1 to 11. The "joining method" shown in Figure 7 indicates the method of joining the shaft portion and the rotor core portion during the manufacture of each of Samples 1 to 11.

[0031] The "bonding strength" shown in FIG. 7 was measured for each of Samples 1 to 11 using a tensile test in which the rotor core and the shaft were gripped and pulled away from each other (in a direction along the central axis of the rotor member). Specifically, the measurement was performed by pulling the shaft inserted into the rotor core as if to pull it out of the rotor core. In each of Samples 1 to 11, the through-holes formed in the rotor core through which the shaft was inserted had two openings of different sizes. Therefore, in the tensile test, the shaft was pulled out of the rotor core from the side with the larger opening. In the tensile test, the force to pull the shaft out of the rotor core was increased at a rate of 10 N / s, and the strength at which the shaft completely peeled off and broke was taken as the "bonding strength."

[0032] 7 indicates whether or not a magnetic portion is provided in the rotor core portion for each of Samples 1 to 11. None of Samples 1 to 11 has a magnetic portion.

[0033] Figure 8 is a cross-sectional view of a rotor of a comparative example. In this evaluation test, the "rotational strength," "iron loss," and "rotational efficiency" shown in Figure 7 each show the results of comparison with the rotor 90 of the comparative example. As shown in Figure 8, the rotor 90 of the comparative example includes a rotor core portion 91, a magnet 92, and a shaft portion 93. In the rotor 90 of the comparative example, the rotor core portion 91 and the shaft portion 93 of the rotor member 900 are integrally formed from laminated electromagnetic steel plates. In the rotor 90 of the comparative example, the magnet 92 is mounted on a surface 911 of the rotor core portion 91.

[0034] The "rotational strength" shown in Figure 7 indicates the durability against torsional stress generated in the rotor components. For the "rotational strength," rotors including Samples 1 to 11 were first fabricated by attaching magnets to each of Samples 1 to 11 and balancing them. The rotation speeds of the rotors fabricated using Samples 1 to 11 and the comparative rotor 90 were gradually increased, and the strength at breakage was measured. Regarding the strength at breakage of the rotors including each sample, the magnitude of the strength of each of Samples 1 to 11 relative to the comparative rotor 90 was taken as the "rotational strength" for each of Samples 1 to 11, and the magnitude of the "rotational strength" was classified into the following symbols: A, B, and C. A: 5% or more higher than the comparative rotor. B: 3% to less than 5% higher than the comparative rotor. C: Similar to the comparative rotor (less than 3%).

[0035] The "iron loss" shown in FIG. 7 was calculated using the method of JIS C 4034-2-1. Specifically, the loss of each motor was measured using the method of JIS C 4034-2-1 for a motor equipped with each of Samples 1 to 11 and a motor equipped with the rotor 90 of the comparative example (hereinafter referred to as the "comparative example motor"). Next, the iron loss of each motor was calculated by subtracting the copper loss calculated using the current flowing through the motor and the mechanical loss calculated from friction, etc., from the measured loss. Regarding the calculated iron loss value of each motor, the magnitude of the iron loss of each of Samples 1 to 11 relative to the comparative example motor was defined as the "iron loss" of each of Samples 1 to 11, and the magnitude of the "iron loss" was classified into the following symbols, A and B. A: 95% or more but less than 100% compared to the comparative example motor B: Similar to the comparative example motor

[0036] The "rotational efficiency" shown in Figure 7 indicates the ratio of output to input in a motor, i.e., the efficiency of the motor. For "rotational efficiency," first, the output of the motors equipped with each of Samples 1 to 11 and the motor of the comparative example was measured when rotated at a predetermined rotation speed. The degree of the magnitude of the output measured for the motors equipped with each of Samples 1 to 11 relative to the output measured for the motor of the comparative example was taken as "rotational efficiency" and classified into the following symbols A and B: A: Efficiency improved by 1% or more compared to the motor of the comparative example B: Efficiency at the same level as the motor of the comparative example

[0037] In terms of the "rotational strength" shown in Figure 7, Samples 1 to 10, whose rotor cores are made of ceramic, were confirmed to exhibit superior performance compared to the comparative rotor 90. The comparative rotor 90 has a rotor core made of relatively heavy electromagnetic steel, which is the outermost rotor when the rotor member rotates. Therefore, gradually increasing the rotation speed increases the torsional stress, making it prone to breakage when rotated at high speeds. On the other hand, Samples 1 to 10 have rotor cores made of relatively lightweight ceramic, which makes it difficult for the torsional stress to increase even when the rotation speed increases gradually. This results in high "rotational strength" and makes them less susceptible to breakage even when rotated at high speeds. Furthermore, the rotor cores of Samples 1 to 10 have low iron loss, which reduces input loss compared to the comparative rotor 90. Therefore, Samples 1 to 10 can be efficiently rotated at high speeds. The reason why the "rotational strength" of sample 11, in which the "material" of the rotor core is epoxy resin, was rated C is thought to be that the shaft portion was formed from an aluminum alloy, which has a significantly larger thermal expansion coefficient than epoxy resin, and the aluminum alloy expanded due to heat generated by mechanical loss, etc., causing damage to the rotor core portion.

[0038] It was also confirmed that, among Samples 1 to 10, Samples 7 to 10, which have a "bonding strength" of 200 N or more, exhibit superior performance in "rotation strength" to Samples 1 to 6, which have a "bonding strength" of less than 200 N. Furthermore, among Samples 1 to 10, Samples 7 to 10, which have a "thermal expansion coefficient difference" of 3×10－６ Samples 7 to 10, in which the difference in thermal expansion coefficient is 3×10 －６ It was confirmed that the "rotational strength" was superior to that of Samples 1 to 6, which had a "thermal expansion coefficient difference" of 3×10 －６ / K or less, the relationship between the size of the shaft portion and the size of the rotor core portion remains almost unchanged even if the temperature of the rotor components rises. This allows the joined state to be maintained by a joint having a certain level of joint strength or more.

[0039] In terms of "iron loss" shown in Figure 7, it was confirmed that Samples 1 to 10, whose rotor cores are made of ceramic, exhibited better performance than the motors of the comparative example. This is because ceramics are less susceptible to hysteresis loss and eddy current loss. In terms of "rotation efficiency" shown in Figure 7, it was confirmed that Samples 1 to 10, whose rotor cores are made of ceramic, exhibited performance comparable to the motors of the comparative example and Sample 11, whose rotor cores are made of epoxy resin.

[0040] According to the rotor member 100 of this embodiment described above, the rotor core portion 120 having the through hole 121 into which the shaft portion 110 is inserted rotates outside the shaft portion 110 when the shaft portion 110 rotates in the motor 1. Because the rotor core portion 120 is made of a relatively lightweight ceramic, the input (electric power) required to rotate the rotor member 100 can be made relatively small. Furthermore, because the rotor core portion 120 is made of ceramic, iron loss is reduced. This reduces input loss compared to when the rotor core portion 120 is made of electromagnetic steel plate. Therefore, the rotor member 100 can be rotated efficiently.

[0041] Furthermore, according to the rotor member 100 of this embodiment, the rotor core portion 120 is formed from ceramic, and therefore the iron loss generated in the rotor core portion 120 can be made smaller than that of electromagnetic steel sheet, iron, etc. This makes it possible to suppress the temperature rise in the rotor core portion 120.

[0042] Furthermore, according to the rotor member 100 of this embodiment, the shaft portion 110 and the rotor core portion 120 are formed from separate members and are joined by the joint portion 130. As a result, the rotor member 100 can be produced by combining a member having a generally rod shape and a member having a generally cylindrical shape, making it relatively easy to produce.

[0043] Furthermore, according to the rotor member 100 of this embodiment, the shaft portion 110 is made of a nickel alloy. That is, since the shaft portion 110 is made of a metal with relatively high thermal conductivity, heat from the rotor core portion 120 can be quickly released.

[0044] Furthermore, according to the rotor member 100 of this embodiment, the rotor core 120 is formed from a mixture of alumina and zirconia, which are relatively lightweight ceramics. As a result, even when the rotor member 100 rotates at high speed, the torsional stress generated when the rotor member 100 rotates is unlikely to increase. Therefore, the rotor member 100 is unlikely to break even when rotated at high speed, and can therefore be rotated at high speed.

[0045] According to the rotor member 100 of this embodiment, the shaft portion 110 and the rotor core portion 120 are joined by the joint 130 having a joining strength of 200 N or more. The absolute value of the difference between the thermal expansion coefficient of the shaft portion 110 and the thermal expansion coefficient of the rotor core portion 120 is 3×10 －６ / K or less, even if the temperature of the rotor member 100 rises, the relationship in size between the shaft portion 110 and the rotor core portion 120, for example, the size of the gap between the shaft portion 110 and the rotor core portion 120 at the through hole 121, is unlikely to change. This makes it possible to maintain the state in which the shaft portion 110 and the rotor core portion 120 are joined by the joining portion 130. Therefore, damage due to torsional stress can be suppressed.

[0046] Furthermore, according to the rotor member 100 of this embodiment, the inner diameter of the through hole 121 decreases from one opening 121 a to the other opening 121 b. The shaft portion 110 inserted into the through hole 121 comes into contact with the inner wall of the through hole 121 and is securely fixed to the rotor core portion 120 by friction with the rotor core portion 120. This makes it difficult for the shaft portion 110 to come out of the through hole 121, thereby suppressing damage caused by torsional stress that occurs when the rotor member 100 rotates.

[0047] Furthermore, according to the motor 1 of this embodiment, the motor 1 includes the rotor member 100 made of ceramic, which reduces iron loss and mechanical loss in the rotor 10. This suppresses a temperature rise in the rotor 10, thereby suppressing a temperature rise in the entire motor 1.

[0048] 9 is a cross-sectional view of a rotor including a rotor member according to a second embodiment. The rotor member of the rotor according to the second embodiment differs from the rotor member of the first embodiment (FIG. 1) in that it includes a magnetic portion.

[0049] Similar to the rotor 10 of the first embodiment, the rotor 40 of the second embodiment is provided in a motor 2 that includes a stator 20 and a motor case 30. The rotor 40 includes a rotor member 400, a magnet 440, and a magnetic portion 450. The rotor 40 is provided on the central axis C2 of the motor 2 and is rotatable about the central axis C2.

[0050] Fig. 10 is a perspective view of a rotor member of this embodiment. Fig. 11 is a cross-sectional view of the rotor member of this embodiment, including a central axis C400 of the rotor member 400. The rotor member 400 includes a rotor core portion 420 formed of ceramic and having a shaft portion 110, a through hole 421 into which the shaft portion 110 is inserted, and a support portion 422 for supporting a magnet 440, and a joint portion 130 that joins the shaft portion 110 and the rotor core portion 420. The rotor member 400 of this embodiment is formed by joining the shaft portion 110 and the rotor core portion 420, which are formed from separate members, via the joint portion 130.

[0051] As shown in FIG. 10 , the rotor core portion 420 has a generally cylindrical shape. The through-hole 421 into which the shaft portion 110 is inserted is formed along the central axis C400 of the rotor member 400. The through-hole 421 is formed such that the inner diameter changes between one opening 421a formed in one end face 423 of the two end faces 423, 424 of the generally cylindrical rotor core portion 420 and the other opening 421b formed in the other end face 424 (see FIG. 11 ). Specifically, the inner diameter Ra of the one opening 421a is larger than the inner diameter Rb of the other opening 421b. In this embodiment, the through-hole 421 is formed such that the inner diameter decreases from the one opening 421a toward the other opening 421b. As a result, when the shaft portion 110 is inserted into the through-hole 421 from one of the openings 421 a, the shaft portion 110 is fixed to the rotor core portion 420 also by the frictional force between the outer wall of the shaft portion 110 and the inner wall of the through-hole 421 .

[0052] The support portion 422 forms an insertion hole having an opening in one end face 423 of the two end faces 423, 424 of the rotor core portion 420, which has a substantially cylindrical shape. In the present embodiment, the opening portion of the support portion 422 is formed to have an annular shape, and a plurality of magnets 440 are provided in the support portion 422. An opening portion of an insertion hole 425 into which the magnetic portion 450 is inserted is provided in one end face 423 of the rotor core portion 420. The opening portion of the insertion hole 425 is located inside the opening portion of the support portion 422. In the present embodiment, a plurality of insertion holes 425 are formed so that one magnetic portion 450 is positioned across two adjacent magnets 440 among the plurality of magnets 440 supported by the support portion 422.

[0053] In this embodiment, the rotor core portion 420 is made of ceramic. ２ O ３ ) and zirconia (ZrO ２ ) (thermal expansion coefficient: 9.2 × 10 －６ / K). In this embodiment, the absolute value of the difference between the thermal expansion coefficient of the shaft portion 110 and the thermal expansion coefficient of the rotor core portion 420 is 0 / K or more and 3×10 －６ / K or less, i.e., 0 / K. The material forming the shaft portion 110 is not limited to nickel alloy, but may be other alloys such as iron alloys and titanium alloys, or ceramics. The material forming the rotor core portion 420 is preferably at least one of oxides, carbides, and nitrides of ceramics.

[0054] 12 is an enlarged view of portion B in FIG. 11 . The distance between the shaft portion 110 and the rotor core portion 420 at the through hole 421 is greater at the load side end 111 of the shaft portion 110 than at the anti-load side end 112 of the shaft portion 110, and the distance Ga on the load side end 111 side is greater than the distance Gb on the anti-load side end 112 side. The solder, which is the joint portion 130, joins the shaft portion 110 and the rotor core portion 420 by entering between the shaft portion 110 and the rotor core portion 420 at the through hole 421. In this embodiment, the joint strength between the shaft portion 110 and the rotor core portion 420 by the joint portion 130 is 200 N or more and 500 N or less. Note that the method of joining the shaft portion 110 and the rotor core portion 420 is not limited to this.

[0055] FIG. 13 is a perspective view of the rotor of this embodiment. FIG. 14 is a cross-sectional view of the rotor of this embodiment. The magnets 440 are supported by support portions 422 of the rotor core portion 420. In this embodiment, the ten magnets 440 are supported by the rotor core portion 420 by being inserted into insertion holes formed by the support portions 422 of the rotor core portion 420. In other words, the motor 2 of this embodiment is a so-called IPM motor in which the magnets 440 are mounted inside the rotor core portion 420. Note that the magnets 440 may be fixed to the insertion holes formed by the support portions 422 with an adhesive (resin), or may be fixed directly to the rotor core portion 420 (for example, by welding) without using an adhesive.

[0056] The magnetic portion 450 is provided in the rotor core portion 420 and is made of metal or soft magnetic ceramic. Materials for forming the magnetic portion 450 include iron (Fe), cobalt (Co), nickel (Ni), nanocrystalline soft magnetic material having nano-sized crystals in an amorphous (non-crystalline) alloy, electromagnetic steel sheet, ferrite (Fe ２ O ３ The magnetic portions 450 of this embodiment are formed of an electromagnetic steel plate. The ten magnetic portions 450 are inserted into the ten insertion holes 425 of the rotor core 420, respectively.

[0057] Fig. 15 is a diagram illustrating a magnetic circuit formed in the rotor of this embodiment. For convenience of illustration, Fig. 15 shows only the cross section of the rotor 40 also shown in Fig. 14. In this embodiment, the magnet 440 forms a magnetic circuit Mgc that passes through the magnetic portion 450.

[0058] Next, an example of a method for manufacturing the rotor member 400 of this embodiment will be described. The method for manufacturing the rotor member 400 is a method similar to the method for manufacturing the rotor member 100 of the first embodiment. The method for manufacturing the rotor member 400 differs from the method for manufacturing the rotor member 100 in that a molded extruded body is machined to have portions that become the through holes 421, portions that become the support portions 422, and insertion holes 425 into which the magnetic portions 450 are inserted, to produce a machined molded body having the shape of the rotor member 400. Note that the method for manufacturing the rotor member 400 shown here is an example, and is not limited to this manufacturing method.

[0059] Next, an evaluation test of the rotor member according to this embodiment will be described. In this evaluation test, five types of samples of rotor members to be used in IPM motors were fabricated, and the rotational strength, iron loss, and rotational efficiency of each of the five samples were evaluated.

[0060] Fig. 16 is a diagram illustrating the evaluation results of the rotor member. Each of Samples 12 to 16 used in this evaluation test was produced by a method similar to the manufacturing method for the rotor member 400 of this embodiment. For each of Samples 12 to 16, materials were selected so that the shaft portion and rotor core portion each had the composition of the "material" shown in Fig. 16. Note that Al, which is the "material" for the rotor core portion in Samples 12 to 16, ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0061] The "thermal expansion coefficient" shown in FIG. 16 indicates the thermal expansion coefficient of the "material" forming each of Samples 12 to 16. The "thermal expansion coefficient difference" shown in FIG. 16 indicates the absolute value of the difference between the thermal expansion coefficient of the material forming the shaft portion and the thermal expansion coefficient of the material forming the rotor core portion for each of Samples 12 to 16. The "joining method" shown in FIG. 16 indicates the method of joining the shaft portion and the rotor core portion during the manufacture of each of Samples 12 to 16. The "joining strength" shown in FIG. 16 indicates the value measured using the same method (tensile test) as the method used in the evaluation test of the first embodiment.

[0062] The "magnetic portion" shown in Figure 16 indicates the material that forms the magnetic portion provided in the rotor core for each of Samples 12 to 16. Sample 12 has a magnetic portion formed from ferrite, while Sample 13 has a magnetic portion formed from a nanocrystalline soft magnetic material. Samples 14 to 16 each have a magnetic portion formed from an electromagnetic steel sheet.

[0063] FIG. 17 is a cross-sectional view of a rotor of a comparative example. In this evaluation test, the "rotational strength," "iron loss," and "rotational efficiency" shown in FIG. 16 each show the results of comparison with a rotor 95 of a comparative example. As shown in FIG. 17, the rotor 95 of the comparative example includes a rotor core portion 96, a magnet 97, and a shaft portion 98. In the rotor 95 of the comparative example, the rotor core portion 96 and the shaft portion 98 of a rotor member 950 are integrally formed from laminated electromagnetic steel plates. In the rotor 95 of the comparative example, the magnet 97 is inserted into a support portion 961 of the rotor core portion 96.

[0064] As in the first embodiment, the "rotational strength," "iron loss," and "rotational efficiency" shown in FIG. 16 were evaluated using the same threshold values ​​as in the first embodiment, with the comparative rotor member 950 or a motor including the comparative rotor member 950 as the evaluation standard. As a result, as shown in FIG. 16, it was confirmed that, in terms of "rotational strength," each of Samples 12 to 16, in which the "material" of the rotor core portion is ceramic, exhibited superior performance (evaluated as "A") compared to the motor including the comparative rotor member 950. This is because, in each of Samples 12 to 16, the "difference in thermal expansion coefficient" was 3×10 －６ / K or less and the "joint strength" was 200 N or more. As with the "rotational strength," it was also confirmed that each of Samples 12 to 16 exhibited superior performance (evaluation "A") in terms of "iron loss" as well as in terms of "rotational strength" compared to the motor equipped with the rotor member 950 of the comparative example.

[0065] The "Rotational Efficiency" shown in Figure 16 confirmed that all of Samples 12 to 16, which include magnetic portions, exhibited superior performance (rated "A") compared to the motor including the comparative rotor member 950, which does not include magnetic portions. By including magnetic portions, the magnetic circuit formed by the magnets passes preferentially through the magnetic portions, further reducing iron loss in the ceramic portion of the rotor core. This further suppresses temperature rise in the rotor core, thereby suppressing increases in mechanical loss such as friction. Therefore, even with the same input, it is believed that including magnetic portions can improve motor output.

[0066] According to the rotor member 400 of this embodiment described above, the rotor core portion 420 having the through hole 421 into which the shaft portion 110 is inserted rotates outside the shaft portion 110 when the shaft portion 110 rotates in the motor. Because the rotor core portion 420 is made of a relatively lightweight ceramic, the input power required to rotate the rotor member 400 can be made relatively small. This allows the rotor member 400 to rotate efficiently at high speed.

[0067] Furthermore, according to the rotor 40 of this embodiment, the rotor core 420 is provided with a magnetic section 450 through which a magnetic circuit formed by a magnet passes. The rotor member 400 including the rotor core 420 made of ceramic has relatively small iron loss and mechanical loss, and therefore is less likely to experience a rise in temperature. This also suppresses a rise in temperature of the magnetic section 450 provided in the rotor core 420, thereby suppressing a decrease in performance of the magnetic section 450.

[0068] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0069] [Variation 1] In the above-described embodiment, the shaft portion 110 is formed from a nickel alloy. The material for forming the shaft portion is not limited to this. It is not limited to nickel alloy, and may be other alloys such as iron alloys and titanium alloys, or ceramics. By forming the shaft portion 110 from a material with relatively high thermal conductivity, heat from the rotor core portion can be quickly released.

[0070] [Modification 2] In the above-described embodiment, the rotor member has the shaft portion and the rotor core portion joined by a joint having a joint strength of 200 N or more. The joint strength between the shaft portion and the rotor core portion by the joint may be less than 200 N, but is preferably greater.

[0071] [Modification 3] In the above-described embodiment, the absolute value of the difference between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion is 3×10 －６ / K or less. The relationship between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion is not limited to this. －６ / K, but the smaller the absolute value of the difference in thermal expansion coefficients, the less likely the size of the gap between the shaft portion and the rotor core portion in the through hole will change even if the temperature of the rotor member changes. This makes it possible to maintain the state in which the shaft portion and the rotor core portion are joined by the joint portion.

[0072] [Modification 4] In the above-described embodiment, the through hole has an inner diameter that decreases from one opening to the other. However, the shape of the through hole is not limited to this. The inner diameter may be the same from one opening to the other opening.

[0073] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0074] <Application Example 1> A rotor member for a motor, comprising: a shaft portion; and a rotor core portion formed of ceramic, the rotor core portion having a through hole into which the shaft portion is inserted and a support portion for supporting a magnet. <Application Example 2> The rotor member described in Application Example 1 further comprises a joint portion that joins the shaft portion and the rotor core portion, the joint strength between the shaft portion and the rotor core portion by the joint portion being 200 N or more, and the absolute value of the difference between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion being 3×10 －６ / K or less. <Application Example 3> The rotor member according to Application Example 1 or Application Example 2, wherein the inner diameter of the through-holes decreases from one opening to the other opening. <Application Example 4> A rotor for a motor, comprising: the rotor member according to any one of Application Examples 1 to 3; a magnet supported by the support portion; and a magnetic portion provided in the rotor core portion and formed of metal or ceramic having soft magnetic properties, wherein the magnet forms a magnetic circuit passing through the magnetic portion. <Application Example 5> A motor, comprising: the rotor member according to any one of Application Examples 1 to 3; a magnet supported by the support portion; and a motor stator arranged outside the rotor core portion and having windings for generating a magnetic field.

[0075] DESCRIPTION OF SYMBOLS 1, 2... Motor 10, 40... Rotor 20... Stator 100, 400... Rotor member 110... Shaft portion 120, 420... Rotor core portion 121, 421... Through hole 122, 422... Support portion 140, 440... Magnet 450... Magnetic portion 220... Winding Mgc... Magnetic circuit

Claims

1. A rotor component for a motor, comprising: a shaft portion; and a rotor core portion formed of ceramic, the rotor core portion having a through hole into which the shaft portion is inserted and a support portion for supporting a magnet.

2. The rotor member according to claim 1 further comprises a joint that joins the shaft portion and the rotor core portion, the joint strength between the shaft portion and the rotor core portion by the joint is 200 N or more, and the absolute value of the difference between the thermal expansion coefficient of the shaft portion and the thermal expansion coefficient of the rotor core portion is 3 x 10 －６ / K or less.

3. A rotor member according to claim 1 or 2, characterized in that the inner diameter of the through-hole decreases from one opening to the other opening.

4. A rotor for a motor, comprising: a rotor member according to claim 1 or claim 2; a magnet supported by the support portion; and a magnetic portion provided in the rotor core portion and formed from a metal or a ceramic having soft magnetic properties, wherein the magnet forms a magnetic circuit passing through the magnetic portion.

5. A motor comprising: a rotor member according to claim 1 or 2; a magnet supported by the support portion; and a stator for the motor, disposed outside the rotor core portion and having windings for generating a magnetic field.

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