Rotor member, rotor, and motor

Abstract

To provide a technique for reducing iron loss and suppressing an increase in mechanical loss in a rotor member for a motor.SOLUTION: A rotor member 100 for a motor includes a rotor core part 110 formed of ceramic and having a support part 111 for supporting a magnet, and a shaft part 120 connected to the rotor core part and formed of ceramic.SELECTED DRAWING: Figure 2

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 reducing iron loss and suppressing an increase in mechanical loss in rotor members for motors.

[0005] An object of the present invention is to provide a technique for reducing iron loss and suppressing an increase in mechanical loss in 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 including: a rotor core portion formed of ceramic and having a support portion for supporting a magnet; and a shaft portion connected to the rotor core portion and formed of ceramic.

[0008] With this configuration, the rotor member is made of ceramic, which allows for smaller iron loss in the rotor member than electromagnetic steel sheets, iron, etc. Furthermore, ceramic, which forms the rotor member, has a smaller thermal expansion coefficient than metal, so the rotor member undergoes less change in size with temperature changes. As a result, even if the temperature of the rotor member changes, for example, the amount of change in friction between the shaft portion and the portion that rotatably supports the shaft portion is smaller, thereby suppressing an increase in mechanical loss in the rotor member.

[0009] (2) In the rotor member of the above embodiment, the ceramic may be at least one of an oxide, a carbide, and a nitride, with an average crystal grain size of 5 μm or less and a porosity of 3% or less. According to this configuration, the rotor member is made of ceramic that is lighter than electromagnetic steel sheet, iron, etc., and is made of at least one of an oxide, a carbide, and a nitride. This reduces mechanical loss in the rotor member. The ceramic forming the rotor member is at least one of an oxide, a carbide, and a nitride, which have relatively high strength, with an average crystal grain size of 5 μm or less and a porosity of 3% or less. This provides the rotor member with relatively high strength, thereby suppressing damage caused by stress generated when the rotor member rotates.

[0010] (3) In the rotor member of the above embodiment, the thermal conductivity of the shaft portion in the axial direction may be 2 W / m·K or more higher than the thermal conductivity in the direction perpendicular to the axial direction. With this configuration, the thermal conductivity of the shaft portion in the axial direction is higher than the thermal conductivity in the direction perpendicular to the axial direction. This makes it easier for heat due to iron loss generated in the rotor core portion to move along the axial direction of the shaft portion. Therefore, it is possible to suppress a temperature rise in the rotor core portion.

[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 a metal or a ceramic having soft magnetic properties, 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 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 made of ceramic, so 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 execute the manufacturing of 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 perspective view of a rotor according to the first embodiment. [Figure 4] FIG. 2 is a cross-sectional view of the rotor of the first embodiment. [Figure 5]5A to 5C are diagrams illustrating evaluation results regarding the rotor member of the first embodiment. [Figure 6] FIG. 10 is a cross-sectional view of a rotor of a comparative example. [Figure 7] FIG. 10 is a cross-sectional view of a motor including a rotor member according to a second embodiment. [Figure 8] FIG. 10 is a perspective view of a rotor member according to a second embodiment. [Figure 9] FIG. 10 is a perspective view of a rotor according to a second embodiment. [Figure 10] FIG. 6 is a cross-sectional view of a rotor according to a second embodiment. [Figure 11] 10A and 10B are diagrams illustrating a magnetic circuit formed in a rotor according to a second embodiment. [Figure 12] 10A and 10B are diagrams illustrating evaluation results regarding the rotor member of the second embodiment. [Figure 13] FIG. 10 is a cross-sectional view of a rotor of a comparative example. [Figure 14] FIG. 4 is a cross-sectional view of a first modified example of the rotor member of the first embodiment. [Figure 15] FIG. 4 is a cross-sectional view of a second modified example of the rotor member of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment 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 power is supplied. The motor 1 includes a rotor 10 having the rotor member 100, 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.

[0016] Fig. 2 is a perspective view of a rotor member of this embodiment. Fig. 3 is a perspective view of the rotor of this embodiment. Fig. 4 is a cross-sectional view of the rotor of this embodiment. The rotor member 100 is made of ceramic and includes a rotor core portion 110 having a support portion 111 for supporting a magnet 130, and a shaft portion 120 made of ceramic and connected to the rotor core portion 110. The rotor 10 includes the rotor member 100 and the magnet 130. The rotor member 100 of this embodiment is made of a single ceramic member.

[0017] As shown in Fig. 2, the rotor core portion 110 has a generally cylindrical shape. The support portions 111 are recessed portions formed on a side surface 112 of the rotor core portion 110, which has a generally cylindrical shape. In this embodiment, four support portions 111 are formed on the side surface 112 of the rotor core portion 110, lined up along the circumferential direction of the rotor core portion 110.

[0018] The shaft portion 120 has two shaft portions 121, 122. Each of the two shaft portions 121, 122 is formed so as to protrude from each of two end faces 113, 114 of the rotor core portion 110, which has a substantially cylindrical shape (see FIG. 1). Each of the shaft portions 121, 122 has a substantially rod shape with its longitudinal direction aligned with the central axis C100 of the rotor member 100. The outer diameter of each of the shaft portions 121, 122 is smaller than the outer diameter of the rotor core portion 110. The end of each of the shaft portions 121, 122 opposite to the end connected to the rotor core portion 110 is exposed to the outside of the motor case 30, which will be described later.

[0019] In the shaft portion 120 of this embodiment, the thermal conductivity in the axial direction of the shaft portion 120, i.e., the thermal conductivity in the direction along the central axis C100 of the rotor member 100, is greater than the thermal conductivity in the direction perpendicular to the axial direction. The thermal conductivity of the shaft portion 120 is measured using a laser flash method. Specifically, the measurement is performed by first preparing an axial measurement sample from the shaft portion 120, measuring 2 mm in the axial direction and 10 mm × 10 mm in the direction perpendicular to the axial direction, and an orthogonal measurement sample, measuring 2 mm in the axial direction and 10 mm × 10 mm in the axial direction. For each of the two measurement samples, the thermal diffusivity is calculated from the temperature response curve of the other main surface when pulsed light energy is applied to one main surface. The calculated thermal diffusivity and the specific heat and density of the measurement sample are used to calculate the axial thermal conductivity and the thermal conductivity in the direction perpendicular to the axial direction. In the shaft portion 120 of this embodiment, the thermal conductivity in the axial direction of the shaft portion 120 is greater than the thermal conductivity in the direction perpendicular to the axial direction by 2 W / m·K or more. This makes it easier for the shaft portion 120 to release the heat of the rotor core portion 110 to the outside of the motor 1.

[0020] The rotor member 100 of this embodiment is made of ceramic. The ceramic forming the rotor member 100 of this embodiment is at least one of oxide, carbide, and nitride. Specifically, the rotor member 100 is made of at least one of oxide-based ceramics such as alumina (Al2O3), silica (SiO2), titanium oxide (TiO2), zirconia (ZrO2), and magnesia (MgO); carbide-based ceramics such as silicon carbide (SiC), boron carbide (B4C), titanium carbide (TiC), and chromium carbide (CrC); and nitride-based ceramics such as aluminum nitride (AlN), silicon nitride (Si3N4), titanium nitride (TiN), and sialon (SiAlON). The material forming the rotor member 100 is identified using X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). The rotor member 100 of this embodiment is made of silicon nitride.

[0021] The ceramic forming the rotor member 100 of this embodiment has an average crystal grain size of 5 μm or less and a porosity of 3% or less. In this embodiment, the average crystal grain size is measured using a linear intercept method. Specifically, a plurality of square measurement ranges, e.g., three to five, each 500 μm on a side, are set on the surface or cross section of the rotor member 100. Next, the number of particles present on the diagonal of each set measurement range is counted, and the length of the diagonal of the measurement range is divided by the number of counted particles to calculate the average crystal grain size for each measurement range. Finally, the average crystal grain size in the rotor member 100 is calculated using the average crystal grain size calculated for each measurement range. The porosity is measured using SEM images captured by a scanning electron microscope. Specifically, an SEM image of a cross section of the rotor member 100 is binarized to distinguish between areas corresponding to crystal grains (white areas) and areas corresponding to pores (black areas). The porosity is calculated by calculating the area of ​​the pores and calculating the ratio to the area of ​​the entire SEM image.

[0022] The magnet 130 is supported by a support portion 111 of the rotor core portion 110. In this embodiment, the magnet 130 is supported by the rotor core portion 110 by being fitted into the support portion 111 of the rotor core portion 110, i.e., a recessed portion formed on the side surface 112 of the rotor core portion 110. In other words, the motor 1 of this embodiment is a so-called SPM motor in which the magnet 130 is mounted on the surface of the rotor core portion 110. The magnet 130 may be fixed to the recessed portion of the support portion 111 with an adhesive (resin), or may be fixed (for example, welded) directly to the rotor core portion 110 without using an adhesive.

[0023] 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 110 and is fixed to the motor case 30, which will be 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.

[0024] 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.

[0025] 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. One of the two shaft portions 121, 122, the shaft portion 121, is inserted through the bearing 310, and the other of the two shaft portions 121, 122, the shaft portion 122, is inserted through the bearing 320. As a result, the rotor 10 is rotatably supported by the motor case 30.

[0026] 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 a sintering aid are weighed as main raw materials. In this embodiment, when the ceramic particles are weighed, ceramic particles corresponding to approximately 5 to 15% of the total weight of the ceramic particles are made into columnar 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 a generally columnar shape. The extrusion direction in the extrusion molding is the longitudinal direction of the rotor member 100, i.e., the direction along the central axis C100 of the rotor member 100. As a result, in the extrusion-molded body, the longitudinal direction of the columnar ceramic particles is arranged along the axial direction of the portion that will become the shaft portion 120, so that the proportion of ceramic in the axial direction of the portion that will become the shaft portion 120 is greater than the proportion of ceramic in the direction perpendicular to the axial direction of the portion that will become the shaft portion 120. Therefore, the thermal conductivity in the axial direction of the shaft portion 120 of the rotor member 100 can be made greater than the thermal conductivity in the direction perpendicular to the axial direction. Next, the extruded body is processed into a portion that will become the shaft portion 120, a portion that will become the support portion 111, and the like, to produce a processed compact having the shape of the rotor member 100. Finally, the processed compact is heated and fired under predetermined conditions to produce the ceramic rotor member 100. In firing the processed compact, the sintering aid that is first weighed out can be a sintering aid that can promote firing of the processed compact even at a relatively low temperature, thereby maintaining the longitudinal direction of the columnar ceramic particles aligned with the axial direction of the portion that will become the shaft portion 120. Note that the manufacturing method of the rotor member 100 shown here is an example and is not limited to this manufacturing method.

[0027] Next, an evaluation test of the rotor member in this embodiment will be described. In this evaluation test, 12 types of rotor members (hereinafter referred to as "samples") for use in SPM motors were produced, differing in any of the rotor member material, average crystal grain size, porosity, thermal conductivity difference, presence or absence of magnetic parts, or material, and the 12 samples were evaluated for "temperature," "rotation efficiency," and "strength."

[0028] FIG. 5 is a diagram illustrating the evaluation results of the rotor member of this embodiment. Of the 12 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, the material of the ceramic particles as the main raw material was selected so as to achieve the composition of the "material" shown in FIG. 5. Sample 11 was manufactured by stacking multiple electromagnetic steel sheets. Sample 12 was manufactured by extruding and processing epoxy resin. The volume ratio of ZrB2 to TiB2 in Sample 2 and the volume ratio of Al2O3 to ZrO2 in Sample 6 were both 7:3.

[0029] The "average grain size" shown in FIG. 5 is a value indicating the average grain size of the ceramic crystal grains forming each of Samples 1 to 10. The "average grain size" was measured using a method similar to the method for measuring the average grain size (linear intercept method) for the rotor member 100 of this embodiment. The "porosity" shown in FIG. 5 is a value indicating the proportion of pores contained in the ceramic forming each of Samples 1 to 10. The "porosity" was measured using a method similar to the method for measuring the porosity for the rotor member 100 of this embodiment (calculating the area of ​​the portion corresponding to the pores in the binarized SEM image). The "thermal conductivity difference" shown in FIG. 5 is a value indicating the difference between the thermal conductivity in the axial direction and the thermal conductivity in the direction perpendicular to the axial direction in the shaft portion for each of Samples 1 to 10. The "thermal conductivity difference" was measured using a method similar to the method for measuring the thermal conductivity difference in the shaft portion 120 of the rotor member 100 of this embodiment (laser flash method).

[0030] FIG. 6 is a cross-sectional view of a rotor of a comparative example. In this evaluation test, the "temperature" and "rotation efficiency" shown in FIG. 5 each show the results of a comparison with a motor equipped with a rotor 90 of a comparative example (hereinafter simply referred to as the "motor of the comparative example"). As shown in FIG. 6, the rotor 90 of the comparative example includes a rotor member 900 having a rotor core portion 91 and a shaft portion 92, and a plurality of magnets 93. In the rotor 90 of the comparative example, the rotor core portion 91 and the shaft portion 92 are formed from laminated electromagnetic steel plates, and the magnets 93 are mounted on a surface 912 of the rotor core portion 91.

[0031] The "temperature" shown in Figure 5 indicates the resistance of the rotor components to temperature rise. The "temperature" was measured using the following method. First, the temperature of the rotor components of the motors equipped with each of Samples 1 to 11 and the motor of the comparative example was measured after rotating at 7500 rpm for one hour. Next, the degree of magnitude of the temperature measured for each of Samples 1 to 11 relative to the temperature of the rotor components of the motor of the comparative example was taken as the "temperature" and classified into the following symbols: S, A, B, and C. S: Greatly reduced by more than 20°C compared to the motor used in the comparison example A: Compared to the comparison motor, the temperature drops by more than 10°C to 20°C or less B: Reduced to 10°C or less compared to the comparison motor C: Temperature similar to that of the motor used in the comparison example

[0032] The "rotational efficiency" shown in Figure 5 indicates the ratio of output to input in a motor, i.e., the efficiency of the motor. "Rotational efficiency" was measured using the following method. First, the output torque of the motors equipped with each of Samples 1 to 11 and the comparative motor was measured after rotating at 7500 rpm for one hour. Next, the ratio of the magnitude of the output torque measured in the motor equipped with each of Samples 1 to 11 to the output torque measured in the comparative motor was taken as the "rotational efficiency" and classified into the following symbols S, A, B, and C. S: 11% or more improvement compared to the comparison motor A: 6% to 11% improvement compared to the comparison motor B: Less than 6% improvement compared to the comparison motor C: Same as the motor used in the comparison example

[0033] The "strength" shown in Figure 5 was measured by the following method. First, the time that the motors equipped with Samples 1 to 10 and Sample 12 could rotate at 10,000 rpm or more without breaking was measured. Next, the length of time that the motors could rotate was taken as the "strength" and classified into the following symbols A, B, and C. A: Rotate for more than 1 hour B: Rotation for 10 minutes or more but less than 1 hour C: Rotation for less than 10 minutes

[0034] In the "temperature" graph shown in Figure 5, Samples 1 to 10, which are made of ceramic, were confirmed to exhibit superior performance to Sample 11, which is made of magnetic steel sheet. Sample 11, which is made of magnetic steel sheet, is prone to iron loss, such as hysteresis loss and eddy current loss, while Samples 1 to 10, which are made of ceramic, are less likely to exhibit iron loss. This suppresses heat generation in the rotor components, making Samples 1 to 10 less susceptible to temperature rise. Furthermore, among Samples 1 to 10, Samples 7 to 10, which have a "thermal conductivity difference" of 2 W / m·K or more, were confirmed to exhibit more suppressed temperature rise than Samples 1 to 6, which have a "thermal conductivity difference" of less than 2 W / m·K. This is thought to be because, in the shaft section, heat from the rotor core moves along the axial direction of the shaft and is easily dissipated from the shaft section.

[0035] The "rotational efficiency" shown in Figure 5 confirmed that Samples 1 to 10, which are made of ceramic, exhibited superior performance to Sample 11, which is made of electromagnetic steel sheet. The electromagnetic steel sheet that forms Sample 11 has a larger thermal expansion coefficient than the ceramic that forms Samples 1 to 10. As a result, Sample 11 tends to increase in size as the temperature rises, and mechanical loss such as friction between the bearing and shaft tends to increase. On the other hand, Samples 1 to 10, which are made of ceramic, have a small thermal expansion coefficient, so they undergo little change in shape as the temperature rises, and an increase in mechanical loss is suppressed. Therefore, it is thought that the reduction in output torque is suppressed compared to the motor of the comparative example, resulting in improved "rotational efficiency."

[0036] Furthermore, among Samples 1 to 10, Samples 4 to 10, in which the ceramic material forming the rotor member is at least one of oxide, carbide, and nitride, were confirmed to exhibit superior performance in terms of "rotational efficiency" compared to Samples 1 to 3, in which the ceramic material is boride. Among ceramics, oxides, carbides, and nitrides are relatively lightweight, which can reduce mechanical loss in the rotor member. This is thought to improve the output torque of the motor.

[0037] In terms of "strength" shown in Figure 5, it was confirmed that Samples 1 to 10, which are made of ceramic, exhibited superior performance to Sample 12, which is made of epoxy resin. Furthermore, among Samples 1 to 10, Samples 4 to 10, in which the ceramic crystals forming the rotor member have an "average particle size" of 5 μm or less and a "porosity" of 3% or less, were confirmed to have greater "strength" than Samples 1 to 3, in which the ceramic crystals have an "average particle size" of greater than 5 μm and a "porosity" of greater than 3%. In other words, it was confirmed that the strength of the rotor member was improved when the ceramic crystals forming the rotor member had an "average particle size" of 5 μm or less and a "porosity" of 3% or less.

[0038] Furthermore, among Samples 1 to 10, Samples 4 to 10, in which the ceramic material forming the rotor member is at least one of oxide, carbide, and nitride, were confirmed to have superior "strength" to Samples 1 to 3, in which the ceramic material is boride. Generally, in ceramics, oxides, carbides, and nitrides have higher strength than borides. This allows motors equipped with Samples 4 to 10 to rotate at higher speeds.

[0039] According to the rotor member 100 of this embodiment described above, the rotor member 100 is formed from ceramic, and therefore the iron loss generated in the rotor member 100 can be made smaller than that of electromagnetic steel sheet, iron, etc. This makes it possible to suppress a temperature rise in the rotor member 100. Furthermore, since the ceramic forming the rotor member 100 has a smaller thermal expansion coefficient than metal, changes in size of the rotor member 100 due to temperature changes are reduced. As a result, even if the temperature of the rotor member 100 rises, the amount of change in friction between the shaft portions 121, 122 and the bearings 310, 320 that rotatably support the shaft portions 121, 122 is reduced, and an increase in mechanical loss in the rotor member 100 can be suppressed. Therefore, a temperature rise in the rotor member 100 due to frictional heat can be suppressed.

[0040] Furthermore, according to the rotor member 100 of this embodiment, it is possible to suppress an increase in mechanical loss in the rotor member 100, thereby reducing loss of output torque due to friction, and thereby suppressing a decrease in output torque of the motor 1.

[0041] Furthermore, according to the rotor member 100 of this embodiment, the rotor member 100 is made of silicon nitride, which is a ceramic that is lighter than electromagnetic steel plate, iron, etc. This reduces mechanical loss in the rotor member 100, thereby improving the output torque of the motor 1.

[0042] Furthermore, according to the rotor member 100 of this embodiment, the rotor member 100 is made of silicon nitride, which has a relatively high strength, and therefore the rotor member 100 is less likely to break even when rotated at high speed.

[0043] Furthermore, according to the rotor member 100 of this embodiment, the average grain size of the ceramic crystals forming the rotor member 100 is 5 μm or less, and the porosity is 3% or less. This gives the rotor member 100 a relatively high strength, and therefore makes it possible to suppress breakage due to stress generated when the rotor member 100 rotates.

[0044] Furthermore, according to the rotor member 100 of this embodiment, the thermal conductivity in the axial direction of the shaft portion 120 is greater by 2 W / m·K or more than the thermal conductivity in the direction perpendicular to the axial direction. This makes it easier for heat generated in the rotor core portion 110 due to iron loss and the like to move along the axial direction of the shaft portion 120. Therefore, it is possible to suppress a temperature rise in the rotor core portion 110.

[0045] 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.

[0046] Second Embodiment 7 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.

[0047] 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 430, and a magnetic portion 440. The rotor 40 is provided on the central axis C2 of the motor 2 so as to be rotatable about the central axis C2.

[0048] Fig. 8 is a perspective view of the rotor member of this embodiment. Fig. 9 is a perspective view of the rotor of this embodiment. Fig. 10 is a cross-sectional view of the rotor of this embodiment. The rotor member 400 includes a rotor core portion 410 formed of ceramic and having a support portion 411 for supporting a magnet 430, and a shaft portion 420 formed of ceramic and connected to the rotor core portion 410. In the rotor member 400 of this embodiment, the rotor core portion 410 and the shaft portion 420 are formed of a single ceramic member, similar to the rotor member 100 of the first embodiment.

[0049] As shown in FIG. 8, the rotor core portion 410 has a substantially cylindrical shape. The support portion 411 of the rotor core portion 410 has an insertion hole with an opening formed in one end face 412 of two end faces 412, 413 of the substantially cylindrical rotor core portion 410. In this embodiment, the opening portion of the support portion 411 is formed to have an annular shape, and as shown in FIG. 9, a plurality of magnets 430 are provided in the support portion 411. The one end face 412 of the rotor core portion 410 has an opening portion of an insertion hole 414 into which a magnetic portion 440 is inserted. The opening portion of the insertion hole 414 is located inside the opening portion of the support portion 411. In this embodiment, a plurality of insertion holes 414 are formed so that one magnetic portion 440 is disposed across two adjacent magnets 430 among the plurality of magnets 430 supported by the support portion 411 (see FIG. 8).

[0050] The shaft portion 420 has two shaft portions 421, 422. The two shaft portions 421, 422 are formed so as to protrude from two end faces 412, 413 of the rotor core portion 410, which has a substantially cylindrical shape (see FIG. 8). Each of the shaft portions 421, 422 has a substantially rod shape with its longitudinal direction aligned with the central axis C400 of the rotor member 400. The outer diameter of each of the shaft portions 421, 422 is smaller than the outer diameter of the rotor core portion 410. The end of each of the shaft portions 421, 422 opposite to the end connected to the rotor core portion 410 is exposed to the outside of the motor case 30.

[0051] The ceramic forming the rotor member 400 of this embodiment is at least one of oxide, carbide, and nitride, with an average crystal grain size of 5 μm or less and a porosity of 3% or less. In the rotor member 400, the thermal conductivity in the axial direction of the shaft portions 421, 422 is greater by 2 W / m·K or more than the thermal conductivity in the direction perpendicular to the axial direction. The rotor member 400 of this embodiment is made of silicon nitride.

[0052] The magnets 430 are supported by support portions 411 of the rotor core portion 410. In this embodiment, the ten magnets 430 are supported by the rotor core portion 410 by being inserted into insertion holes formed in the support portions 411 of the rotor core portion 410. In other words, the motor 2 of this embodiment is a so-called IPM motor in which the magnets 430 are mounted inside the rotor core portion 410. The magnets 430 may be fixed to the insertion holes formed in the support portions 411 with an adhesive (resin), or may be fixed (for example, welded) directly to the rotor core portion 410 without using an adhesive.

[0053] The magnetic portion 440 is provided in the rotor core portion 410 and is made of a metal or a soft magnetic ceramic. Materials for forming the magnetic portion 440 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 440 of this embodiment is made of electromagnetic steel sheets. Ten magnetic portions 440 are inserted into ten insertion holes 414 of the rotor core portion 410, respectively.

[0054] Fig. 11 is a diagram illustrating the magnetic circuit formed in the rotor of this embodiment. For convenience of illustration, Fig. 11 shows only the cross section of rotor 40 also shown in Fig. 10. In this embodiment, magnet 430 forms a magnetic circuit Mgc that passes through magnetic portion 440.

[0055] 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 portion that becomes the shaft portion 420, a portion that becomes the support portion 411, an insertion hole 414 into which the magnetic portion 440 is inserted, and the like are processed in a molded extrusion molded body 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.

[0056] 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 prepared, which differed in any of the following: rotor member material, average crystal grain size, porosity, thermal conductivity difference, presence or absence of magnetic parts, or material, and each of the five types of samples was evaluated for "temperature," "rotation efficiency," and "strength" in the same manner as the evaluation test in the first embodiment.

[0057] Fig. 12 is a diagram illustrating the evaluation results for the rotor member of this embodiment. Each of Samples 13 to 17 used in this evaluation test was produced by a method conforming to the manufacturing method for rotor member 400 of this embodiment. For each of Samples 13 to 17, the material of the ceramic particles as the main raw material was selected so as to achieve the composition of the "material" shown in Fig. 12. The volume ratio of Al2O3 to ZrO2 in Samples 13 to 15 was all 7:3.

[0058] The "average particle size" shown in FIG. 12 is a value indicating the average particle size of the crystal grains of the ceramic forming each of Samples 13 to 17. The "porosity" shown in FIG. 12 is a value indicating the proportion of pores contained in the ceramic forming each of Samples 13 to 17. The "thermal conductivity difference" shown in FIG. 12 is a value indicating the difference between the thermal conductivity in the axial direction and the thermal conductivity in the direction perpendicular to the axial direction in the shaft portion for each of Samples 13 to 17. The "average particle size," "porosity," and "thermal conductivity difference" shown in FIG. 12 were measured using the same method as the method used in the evaluation test of the first embodiment.

[0059] The "magnetic portion" shown in Figure 12 indicates the material forming the magnetic portion provided in the rotor core portion for each of Samples 13 to 17. Sample 13 has a magnetic portion formed from ferrite, and Sample 14 has a magnetic portion formed from a nanocrystalline soft magnetic material. Each of Samples 15 to 17 has a magnetic portion formed from an electromagnetic steel sheet.

[0060] FIG. 13 is a cross-sectional view of a rotor of a comparative example. In this evaluation test, the "temperature" and "rotation efficiency" shown in FIG. 12 each show the results of a comparison with a rotor 95 of a comparative example. As shown in FIG. 13, the rotor 95 of the comparative example includes a rotor member 950 having a rotor core portion 96 and a shaft portion 97, and a plurality of magnets 98. In the rotor 95 of the comparative example, the rotor core portion 96 and the shaft portion 97 are formed from laminated electromagnetic steel plates, and the magnets 98 are inserted into support portions 961 of the rotor core portion 96.

[0061] As with the first embodiment, the "temperature" and "rotation efficiency" shown in Fig. 12 were evaluated using the same threshold values ​​as in the first embodiment, with the comparative rotor member 950 or an IPM motor including the comparative rotor member 950 as the evaluation standard. As a result, as shown in Fig. 12, it was confirmed that, for "temperature," each of Samples 13 to 17, whose "material" was ceramic, exhibited superior performance (evaluated as "S") compared to the IPM motor including the comparative rotor member 950. Furthermore, as with "temperature," it was confirmed that, for "rotation efficiency," each of Samples 13 to 17 exhibited superior performance (evaluated as "S" or "A") compared to the IPM motor including the comparative rotor member 950.

[0062] As in the first embodiment, the "strength" shown in Fig. 12 was determined by measuring the time that the motors equipped with each of Samples 13 to 17 could rotate at 10,000 rpm or more without breaking, and judging the same threshold value as in the first embodiment. As a result, as shown in Fig. 12, it was confirmed that each of Samples 13 to 17 also exhibited excellent performance in "strength" (judgment "A").

[0063] According to the rotor member 400 of this embodiment described above, since the rotor member 400 is made of ceramic, the iron loss generated in the rotor member 400 can be made relatively small. This makes it possible to suppress a temperature rise in the rotor member 400. Furthermore, since the ceramic forming the rotor member 400 has a relatively small thermal expansion coefficient, changes in size of the rotor member 400 due to temperature changes are small. This makes it possible to suppress an increase in mechanical loss in the rotor member 400. Therefore, it is possible to suppress a temperature rise in the rotor member 400 due to frictional heat.

[0064] Furthermore, according to the rotor 40 of this embodiment, the rotor core unit 410 is provided with a magnetic unit 440 through which the magnetic circuit Mgc formed by the magnets 430 passes. The rotor member 400 provided in the rotor core unit 410 has relatively small iron loss and mechanical loss, and therefore is less likely to increase in temperature. This also suppresses the temperature increase in the magnetic unit 440 provided in the rotor core unit 410, making it possible to suppress performance degradation of the magnetic unit 440 due to temperature changes.

[0065] <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.

[0066] [Variation 1] In the above-described embodiment, the rotor member is formed from silicon nitride. However, the ceramic forming the rotor member is not limited to this. As described above, the ceramic forming the rotor member is preferably at least one of oxide, carbide, and nitride, but is not limited to these. When the ceramic forming the rotor member is at least one of oxide, carbide, and nitride, the rotor member becomes relatively lightweight and relatively strong. Therefore, not only is breakage during use suppressed, but the rotor member is also easily manufactured due to its excellent workability.

[0067] [Variation 2] In the above-described embodiment, the ceramic forming the rotor member has an average crystal grain size of 5 μm or less and a porosity of 3% or less. The properties of the ceramic forming the rotor member are not limited to these. The average crystal grain size of the ceramic may be greater than 5 μm, and the porosity may be greater than 3%. When the average crystal grain size is 5 μm or less and the porosity is 3% or less, the strength of the rotor member becomes relatively high.

[0068] [Variation 3] In the above-described embodiment, the thermal conductivity in the axial direction of the shaft portion 120 is set to be 2 W / m·K or more higher than the thermal conductivity in the direction perpendicular to the axial direction. The relationship between the thermal conductivity in the axial direction and the thermal conductivity in the direction perpendicular to the axial direction in the shaft portion is not limited to this. When the thermal conductivity in the axial direction in the shaft portion is higher than the thermal conductivity in the direction perpendicular to the axial direction, heat from the rotor core portion can be more easily released to the outside of the motor.

[0069] [Variation 4] In the above-described embodiment, the rotor member has the rotor core portion and the shaft portion formed from a single ceramic member. However, the relationship between the rotor core portion and the shaft portion is not limited to this.

[0070] Fig. 14 is a cross-sectional view of a first modified example of the rotor member of the first embodiment. In the rotor member 100 shown in Fig. 14, the rotor core portion 110 and the shaft portion 120 are separate members. Specifically, the rotor core portion 110 has a through hole 115 on a central axis C100 of the rotor member 100. The shaft portion 120 is inserted into the through hole 115 and fixed to the rotor core portion 110. Even in the rotor member 100 configured in this manner, the rotor core portion 110 and the shaft portion 120 are made of ceramic, so that iron loss can be reduced and an increase in mechanical loss can be suppressed.

[0071] Fig. 15 is a cross-sectional view of a second modified example of the rotor member of the first embodiment. In the rotor member 100 shown in Fig. 15, the rotor core portion 110 and the shaft portions 121 and 122 are separate members. The shaft portions 121 and 122 are connected to two end faces 113 and 114 of the rotor core portion 110, which has a substantially cylindrical shape, respectively, by an adhesive or the like (not shown). Even in the rotor member 100 configured in this manner, the rotor core portion 110 and the shaft portion 120 are made of ceramic, so that iron loss can be reduced and an increase in mechanical loss can be suppressed.

[0072] 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.

[0073] <Application example 1> A rotor member for a motor, comprising: a rotor core portion formed of ceramic and having a support portion for supporting the magnet; a shaft portion connected to the rotor core portion and formed of ceramic, A rotor member characterized by: <Application example 2> The rotor member according to Application Example 1, the ceramic is at least one of an oxide, a carbide, and a nitride; The average grain size of the crystals is 5 μm or less, and the porosity is 3% or less. A rotor member characterized by: <Application example 3> The rotor member according to Application Example 1 or Application Example 2, the thermal conductivity in the axial direction of the shaft portion is greater by 2 W / m K or more than the thermal conductivity in the direction perpendicular to the axial direction; 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]

[0074] 1, 2...Motor 10,40...Rotor 20...Stator 100,400...Rotor parts 110,410...Rotor core part 111,411...Support part 120,420...shaft section 130,430...Magnet 440...Magnetic part 220...winding Mgc...magnetic circuit

Claims

1. A rotor member for a motor, comprising: a rotor core portion formed of ceramic and having a support portion for supporting the magnet; a shaft portion connected to the rotor core portion and formed of ceramic, A rotor member characterized by:

2. 2. The rotor member according to claim 1, the ceramic is at least one of an oxide, a carbide, and a nitride; The average grain size of the crystals is 5 μm or less, and the porosity is 3% or less. A rotor member characterized by:

3. 3. The rotor member according to claim 1 or 2, The thermal conductivity in the axial direction of the shaft portion is greater by 2 W / m K or more than the thermal conductivity in the direction perpendicular to the axial direction. 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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