Rotor member, rotor, and motor

Abstract

To provide a technique for efficiently rotating a rotor member.SOLUTION: The rotor member 100 has a shaft part 110, a through hole 121 into which the shaft part is inserted, and a support part 122 for supporting a magnet 140, and includes a rotor core part 120 formed of ceramic.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART Rotor members for motors have been known for some time (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-40996 [Patent Document 2] International Publication No. 2018 / 147052 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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 comprising: a rotor core portion made of ceramic, the rotor core portion 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 is 3×10 -6 / K or less, the dimensional relationship between the shaft and rotor core is unlikely to change even if the temperature of the rotor components rises. This allows the shaft and rotor core to remain joined together by the joint. This prevents damage caused by torsional stress that occurs when the rotor components rotate.

[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, a motor is provided. 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. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a motor including a rotor member according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a rotor member according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of a rotor member according to the first embodiment. [Figure 4] FIG. 4 is an enlarged view of part A in FIG. 3. [Figure 5] FIG. 2 is a perspective view of a rotor according to the first embodiment. [Figure 6] FIG. 2 is a cross-sectional view of the rotor of the first embodiment. [Figure 7] 5A to 5C are diagrams illustrating evaluation results regarding the rotor member of the first embodiment. [Figure 8] FIG. 10 is a cross-sectional view of a rotor of a comparative example. [Figure 9] FIG. 10 is a cross-sectional view of a motor including a rotor member according to a second embodiment. [Figure 10] FIG. 10 is a perspective view of a rotor member according to a second embodiment. [Figure 11] FIG. 10 is a cross-sectional view of a rotor member according to a second embodiment. [Figure 12] FIG. 12 is an enlarged view of part B in FIG. [Figure 13] FIG. 10 is a perspective view of a rotor according to a second embodiment. [Figure 14] FIG. 6 is a cross-sectional view of a rotor according to a second embodiment. [Figure 15] 10A and 10B are diagrams illustrating a magnetic circuit formed in a rotor according to a second embodiment. [Figure 16] 10A and 10B are diagrams illustrating evaluation results regarding the rotor member of the second embodiment. [Figure 17] FIG. 10 is a cross-sectional view of a rotor of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment FIG. 1 is a cross-sectional view of a motor including a rotor member of the first embodiment. The rotor member 100 of this embodiment is used in a motor 1 that outputs rotational torque when power is supplied. 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 a rotor member of this embodiment. Fig. 3 is a cross-sectional view of the rotor member of this embodiment, including a 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 ends 111, 112 of the shaft portion 110 both protrude from the rotor core portion 120 and are exposed to the outside of a motor case 30 (described later) as shown in Fig. 1. As shown in Fig. 3, of the two ends 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 111, and the end with the shorter portion protruding from the rotor core portion 120 is referred to as the anti-load side end 112.

[0018] As shown in FIG. 2, the rotor core portion 120 has a substantially 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 rotor core portion 120 having a substantially cylindrical shape 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 opening 121a, 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 the side surface 125 of the rotor core portion 120, which has a substantially cylindrical shape. In this embodiment, the support portions 122 are formed on the side surface 125 of the rotor core portion 120 so as to be lined up in a row of four 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 / K). The rotor core 120 is made of ceramic. The rotor core 120 of this embodiment is made of a mixture of alumina (Al2O3) and zirconia (ZrO2) (thermal expansion coefficient: 9.2 × 10 -6 / K). As a result, 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 × 3 mm × 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 serving as 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 at 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. 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 portion 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 made 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, wool made of ceramic 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 in this embodiment will be described. In this evaluation test, 11 types of rotor members (hereinafter referred to as "samples") were produced that were used in SPM motors and differed 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 "rotation strength," "iron loss," and "rotation efficiency" were evaluated for each of the 11 types of 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. The volume ratio of ZrB2 to Al2O3 in Sample 5 and the volume ratio of Al2O3 to ZrO2 in Samples 8 to 10 were all 7:3.

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

[0031] The "bonding strength" shown in Figure 7 was measured for each of Samples 1 to 11 using a tensile test in which the rotor core and shaft were gripped and pulled away from each other (in the 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 remove it from the rotor core. For each of Samples 1 to 11, the through-holes through which the shafts are inserted have two openings of different sizes. Therefore, in the tensile test, the shaft was removed from the rotor core from the side with the larger opening. In the tensile test, the force required to remove the shaft from 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] FIG. 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 FIG. 7 each show the results of comparison with a rotor 90 of a comparative example. As shown in FIG. 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 FIG. 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 speed was gradually increased for each of the rotors fabricated using Samples 1 to 11 and Comparative Example Rotor 90, 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 Comparative Example 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 rotor for comparison B: 3% to 5% higher than the rotor of the comparative example C: Same as the rotor of the comparison example (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 motor of the comparative example 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% to 100% of the motor used as the comparison example B: Same as the motor used in the comparison example

[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. "Rotational efficiency" was measured by first measuring the output of a motor equipped with each of Samples 1 to 11 and a motor of the comparative example when rotated at a predetermined rotation speed. The degree of magnitude of the output measured for a motor equipped with each of Samples 1 to 11 relative to the output measured for the motor of the comparative example was taken as the "rotational efficiency" and was classified into symbols A and B as shown below. A: Efficiency improved by more than 1% compared to the comparative motor B: Efficiency similar to that of the comparative motor

[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 rotor 90 of the comparative example. The rotor core of the comparative example 90, which is the outermost rotor when the rotor member rotates, is made of a relatively heavy electromagnetic steel plate. Therefore, as the rotation speed gradually increases, torsional stress tends to increase, making the rotor more susceptible to damage when rotated at high speeds. On the other hand, the rotor core of Samples 1 to 10 is made of a relatively lightweight ceramic, so torsional stress is less likely to increase even when the rotation speed gradually increases. This results in higher "rotational strength" and less damage when rotated at high speeds. Furthermore, the rotor cores of Samples 1 to 10 have lower iron loss, reducing input loss compared to the rotor 90 of the comparative example. Therefore, Samples 1 to 10 can be efficiently rotated at high speeds. The "Rotational Strength" of Sample 11, whose rotor core is made of epoxy resin, was rated C. This is thought to be because the shaft is made of aluminum alloy, which has a significantly higher thermal expansion coefficient than epoxy resin. This is because heat generated by mechanical loss, etc. caused the aluminum alloy to expand, damaging the rotor core.

[0038] Furthermore, it was 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 "rotational strength" compared 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, which have a thermal expansion coefficient difference of 3 × 10 -6 It was confirmed that the "rotational strength" was superior to 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 and the size of the rotor core remains almost unchanged even when the temperature of the rotor components rises. This allows the joint to be maintained with a certain level of joint strength.

[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 likely to generate hysteresis loss or 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 makes it possible to reduce input loss compared to when the rotor core portion 120 is made of an 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 an electromagnetic steel sheet, iron, etc. This makes it possible to suppress a 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 with 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, the heat of 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. This prevents the torsional stress generated when the rotor member 100 rotates from becoming large, even when rotated at high speed. Therefore, the rotor member 100 is less likely to break even when rotated at high speed, and can therefore be rotated at high speed.

[0045] Furthermore, 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 121a to the other opening 121b. The shaft portion 110 inserted into the through hole 121 comes into contact with the inner wall of the through hole 121 and is reliably fixed to the rotor core portion 120 by the frictional force 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 due to 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] Second Embodiment 9 is a cross-sectional view of a rotor including a rotor member according to the second embodiment. The rotor member included in the rotor according to the second embodiment differs from the rotor member according to 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 so as to be 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 made 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 made of separate members, via the joint portion 130.

[0051] As shown in FIG. 10, the rotor core portion 420 has a substantially 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 rotor core portion 420, which has a substantially cylindrical shape, 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 opening 421a, 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 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 disposed across two adjacent magnets 440 among the plurality of magnets 440 supported by the support portion 422.

[0053] In this embodiment, the rotor core 420 is made of ceramic. The rotor core 420 in this embodiment is made of a mixture of alumina (Al2O3) and zirconia (ZrO2) (thermal expansion coefficient: 9.2 × 10 -6 / K). As a result, 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 serving as 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. The magnets 440 may be fixed to the insertion holes formed by the support portions 422 with an adhesive (resin), or may be fixed (for example, welded) directly to the rotor core portion 420 without using an adhesive.

[0056] The magnetic portion 450 is provided in the rotor core portion 420 and is made of a metal or a soft magnetic ceramic. Materials for forming the magnetic portion 450 include iron (Fe), cobalt (Co), nickel (Ni), nanocrystalline soft magnetic materials having nano-sized crystals in an amorphous alloy, electromagnetic steel sheets, and soft magnetic ceramics such as ferrite (Fe2O3). The magnetic portion 450 of this embodiment is made of electromagnetic steel sheets. Ten magnetic portions 450 are inserted into ten insertion holes 425 of the rotor core portion 420, respectively.

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

[0058] Next, an example of a manufacturing method for the rotor member 400 of this embodiment will be described. The manufacturing method for the rotor member 400 is a method similar to the manufacturing method for the rotor member 100 of the first embodiment. The manufacturing method for the rotor member 400 differs from the manufacturing method for the rotor member 100 in that a molded extrusion is processed to form a portion that becomes the through-hole 421, a portion that becomes the support portion 422, an insertion hole 425 into which the magnetic portion 450 is inserted, and the like, to produce a processed molded body having the shape of the rotor member 400. Note that the manufacturing method for the rotor member 400 shown here is an example, and the manufacturing method is not limited to this.

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

[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 conforming to the manufacturing method of 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 "material" composition shown in Fig. 16. The volume ratio of Al2O3 to ZrO2, which is the "material" of the rotor core portion in Samples 12 to 16, was all 7:3.

[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 Fig. 16 indicates the material forming the magnetic portion provided in the rotor core portion for each of Samples 12 to 16. Sample 12 is provided with a magnetic portion formed from ferrite, and Sample 13 is provided with a magnetic portion formed from a nanocrystalline soft magnetic material. Samples 14 to 16 are each provided with 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 "rotation strength," "iron loss," and "rotation 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 "rotation 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 rotor member 950 of the comparative example.

[0065] The "Rotational Efficiency" shown in FIG. 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 a magnetic portion. By including a magnetic portion, the magnetic circuit formed by the magnets passes preferentially through the magnetic portion, 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 a magnetic portion 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 force 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] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0069] [Variation 1] In the above-described embodiment, the shaft portion 110 is made of a nickel alloy. However, 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] [Variation 2] In the above-described embodiment, the rotor member has a shaft portion and a rotor core portion joined together 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] [Variation 3] In the above 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 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.

[0072] [Variation 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; 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; A rotor member characterized by: <Application example 2> The rotor member according to Application Example 1 may further include: a joint portion that joins the shaft portion and the rotor core portion, The joining strength between the shaft portion and the rotor core portion at the joining portion is 200 N or more, 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, A rotor member characterized by: <Application example 3> The rotor member according to Application Example 1 or Application Example 2, The through hole has an inner diameter that decreases from one opening to the other opening. A rotor member characterized by: <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; a magnetic portion provided in the rotor core portion and formed of a metal or a ceramic having soft magnetic properties, The magnet forms a magnetic circuit passing through the magnetic portion. A rotor characterized by: <Application example 5> A motor, The rotor member according to any one of Application Examples 1 to 3, a magnet supported by the support portion; a stator for the motor, the stator being disposed outside the rotor core and having a winding for generating a magnetic field; A motor characterized by: [Explanation of symbols]

[0075] 1, 2...Motor 10,40...Rotor 20...Stator 100,400...Rotor parts 110...shaft section 120,420...Rotor core 121,421...Through holes 122,422…Support part 140,440...Magnet 450...Magnetic part 220...winding Mgc...magnetic circuit

Claims

1. A rotor member for a motor, comprising: A shaft portion; 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; A rotor member characterized by:

2. The rotor member according to claim 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 at the joint is 200 N or more, 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, A rotor member characterized by:

3. 3. The rotor member according to claim 1 or 2, The through hole has an inner diameter that decreases from one opening to the other opening. A rotor member characterized by:

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

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

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