Rotor member, rotor, axial gap motor, and motor

Abstract

A rotor member for a motor, said rotor member comprising: a rotor core part formed from ceramic and having a support part for supporting a magnet; and a shaft part connected to the rotor core part and formed from ceramic.

Description

Rotor member, rotor, axial gap motor, and motor

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

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

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

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

[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, the average grain size of the crystal grains may be 5.0 μm or less, and the porosity may be 3% or less. According to this configuration, the rotor member is made of a ceramic that is lighter than electromagnetic steel sheet, iron, or the like, and is formed of at least one of an oxide, a carbide, and a nitride. This reduces mechanical loss in the rotor member. Furthermore, the ceramic forming the rotor member is at least one of an oxide, a carbide, and a nitride, which have relatively high strength, the average grain size of the crystal grains may be 5.0 μm or less, and the porosity may be 3% or less. This allows the rotor member to have relatively high strength, thereby suppressing damage due to 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 at least 2 W / (m·K) greater than the thermal conductivity in the direction perpendicular to the axial direction. According to this configuration, the thermal conductivity of the shaft portion in the axial direction is greater than the thermal conductivity in the direction perpendicular to the axial direction. This allows heat due to iron loss generated in the rotor core portion to more easily move along the axial direction of the shaft portion. Therefore, the temperature rise of the rotor core portion can be suppressed.

[0011] (4) In the rotor member of the above aspect, the rotor core portion and the shaft portion may be formed from a single ceramic member. According to this configuration, the rotor core portion and the shaft portion of the rotor member are each formed from ceramic. This reduces iron loss generated in the rotor member and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, because the rotor core portion and the shaft portion are formed from a single ceramic member, heat generated in the rotor core portion is easily transferred to the shaft portion. This makes it easier for heat generated in the rotor core portion to be released to the outside of the motor via the shaft portion, thereby suppressing a temperature rise in the rotor member.

[0012] (5) In addition, in the rotor member of the above embodiment, the thermal expansion coefficient is 6.0 × 10 －６ / K or less, and the specific gravity is 5.0 g / cm ３ The following may be true. With this configuration, since the rotor member has a relatively small coefficient of thermal expansion, an increase in mechanical loss can be suppressed even when the temperature rises. This reduces output loss due to friction. Furthermore, since the specific gravity of the rotor member is relatively small, it can be rotated with a relatively small force. Therefore, the power required to rotate the rotor member at a predetermined rotation speed can be relatively small.

[0013] (6) In the rotor member of the above aspect, the rotor core portion may have a generally columnar shape, the shaft portion may be formed so as to protrude from an end face of the rotor core portion, and a connection portion between the rotor core portion and the shaft portion may be formed so as to have an R-shape (curved shape) with an R (radius of curvature) of 0.2 mm or more. According to this configuration, the connection portion between the rotor core portion and the shaft portion formed so as to protrude from the end face of the rotor core portion is formed so as to have an R-shape with an R of 0.2 mm or more. This makes it difficult for stress generated in the rotor member to concentrate at the connection portion, thereby suppressing damage to the rotor member.

[0014] (7) In the rotor member of the above aspect, the shaft portion may have a plurality of crystal grains and a grain boundary liquid phase surrounded by the crystal grains, and the grain boundary liquid phase may account for less than 10% of the cross section of the shaft portion in terms of area ratio. According to this configuration, the rotor core portion and the shaft portion of the rotor member are each formed of ceramic. This reduces iron loss generated in the rotor member and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, the grain boundary liquid phase accounts for less than 10% of the cross section of the shaft portion in terms of area ratio. This facilitates heat transfer in the shaft portion, making it easier to dissipate heat generated in the rotor core portion to the outside of the motor via the shaft portion. Therefore, temperature rise in the rotor member can be suppressed.

[0015] (8) In the rotor member of the above aspect, the shaft portion may have crystal grains with an average grain size of 5.0 μm or less. With this configuration, the strength of the shaft portion is relatively high because the average grain size of the crystal grains in the shaft portion is 5.0 μm or less. This makes it possible to suppress breakage.

[0016] (9) In the rotor member of the above aspect, the shaft portion may have a surface roughness Ra of 15 μm or less. With this configuration, the surface roughness Ra of the shaft portion is relatively small, thereby reducing the frictional force between the shaft portion and the portion that rotatably supports the shaft portion. This allows the rotor member to rotate at a higher speed.

[0017] (10) 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. A rotor member including a rotor core portion is less likely to increase in temperature because iron loss and mechanical loss are relatively small. This suppresses temperature rise in the magnetic portion provided in the rotor core portion, thereby suppressing performance degradation of the magnetic portion.

[0018] (11) According to yet another aspect of the present invention, a rotor for a motor is provided. The rotor includes the rotor member described above and a magnet disposed inside or on the outer surface of the rotor core. With this configuration, the rotor core and shaft of the rotor member are formed of ceramic, thereby reducing iron loss in the rotor core and other components compared to magnetic steel sheets or iron. Furthermore, ceramics forming the shaft have a smaller thermal expansion coefficient than metals, reducing changes in size of the shaft due to temperature changes. This reduces the amount of change in friction between the shaft and a portion that rotatably supports the shaft, even when the temperature of the shaft changes. Therefore, increases in mechanical loss due to temperature changes in the rotor can be suppressed.

[0019] (12) The rotor of the above embodiment may further include a magnetic portion provided in the rotor core and made of a soft magnetic material, and the magnet may form a magnetic circuit passing through the magnetic portion. According to this configuration, the rotor is provided with a magnetic portion through which the magnetic circuit formed by the magnet passes. The rotor core is made of ceramic and has relatively low iron loss, which can improve the ratio of output to input to the motor, i.e., motor efficiency. Furthermore, a rotor with relatively low iron loss and mechanical loss is less likely to increase in temperature. This suppresses temperature increases in the magnetic portion, thereby suppressing performance degradation of the magnetic portion due to temperature increases.

[0020] (13) In the rotor of the above aspect, the magnets may be arranged in the rotor core portion so as to form a Halbach array. According to this configuration, the magnets are arranged in the rotor core portion so as to form a Halbach array. The rotor core portion is made of ceramic and has relatively small iron loss, so the magnetic field strength generated by the magnets in a specific direction can be further strengthened. This can further improve the efficiency of the motor.

[0021] (14) In the rotor of the above aspect, the rotor core portion may have a substantially circular plate shape, the shaft portion may be connected to the center of the rotor core portion so that its axial direction is perpendicular to the main surface of the rotor core portion, and the magnet may be arranged in the rotor core portion so that its longitudinal direction is perpendicular to the axial direction of the shaft portion. According to this configuration, the shaft portion is connected to the center of the rotor core portion so that its axial direction is perpendicular to the main surface of the rotor core portion, and the magnet is arranged in the rotor core portion so that its longitudinal direction is perpendicular to the axial direction of the shaft portion. As a result, a motor including the rotor of the above aspect can be an axial gap motor in which the main direction of the magnetic flux in the magnetic circuit formed by the magnet is along the axial direction of the shaft portion. The rotor core portion of the rotor of the above aspect is made of ceramic with relatively low iron loss, which further improves the efficiency of the axial gap motor.

[0022] (15) In the rotor of the above aspect, the rotor core may include two plate-shaped members having a substantially circular shape, the magnets being arranged on one of a pair of main surfaces of each of the two plate-shaped members, and the shaft may be connected to the two plate-shaped members so that the magnets arranged on each of the two plate-shaped members face each other. According to this configuration, in the rotor, the magnets are arranged on the opposing main surfaces of the pair of main surfaces of each of the two plate-shaped members connected by the shaft in the rotor core. This allows a motor including the rotor of the above aspect to be an axial gap motor in which the main direction of the magnetic flux in the magnetic circuit formed by the magnets is along the axial direction of the shaft. The rotor core of the rotor of the above aspect is made of ceramic with relatively low iron loss, further improving the efficiency of the axial gap motor.

[0023] (16) According to yet another aspect of the present invention, there is provided an axial gap motor. This axial gap motor includes the rotor described above and a motor stator having windings for generating a magnetic field, the magnetic field being formed such that the direction of magnetic flux is along the axial direction of the shaft portion. With this configuration, in the axial gap motor, the rotor core portion and the shaft portion are formed from ceramic, so that iron loss generated in the rotor core portion and the like can be made smaller than with electromagnetic steel sheet or iron, etc. This can further improve the efficiency of the axial gap motor.

[0024] (17) According to yet another aspect of the present invention, a motor is provided. The motor includes the rotor described above and a motor stator disposed outside the rotor core and having windings for generating a magnetic field. With this configuration, the motor includes a rotor core and a shaft formed from 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. Therefore, it is possible to suppress a decrease in motor efficiency due to temperature rise.

[0025] (18) 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 core and a shaft formed from 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. Therefore, it is possible to suppress a decrease in motor efficiency due to temperature rise.

[0026] The present invention can be realized in various forms, for example, in the form of an apparatus using a rotor member, an apparatus including a rotor, an apparatus including an axial gap motor, an apparatus including a motor, a method for manufacturing a rotor member, a method for manufacturing a rotor or motor including a rotor member, a computer program that causes a computer to execute the manufacture of a rotor member, etc.

[0027] 8 is a cross-sectional view of a motor including a rotor member of the first embodiment. FIG. 9 is a perspective view of a rotor member of the first embodiment. FIG. 10 is a perspective view of a rotor of the first embodiment. FIG. 11 is a cross-sectional view of a rotor of the first embodiment. FIG. 12 is a diagram explaining evaluation results for the rotor member of the first embodiment. FIG. 13 is a cross-sectional view of a rotor of a comparative example. FIG. 14 is a diagram explaining evaluation results for the rotor of the first embodiment. FIG. 14 is a cross-sectional view of a motor including a rotor member of the second embodiment. FIG. 15 is a perspective view of a rotor of the second embodiment. FIG. 16 is an enlarged view of part A of FIG. 10. FIG. 17 is a diagram explaining evaluation results for the rotor member of the second embodiment. FIG. 18 is a diagram explaining evaluation results for the rotor member of the third embodiment. FIG. 19 is a cross-sectional view of a motor including a rotor member of the fourth embodiment. FIG. 19 is a perspective view of a rotor of the fourth embodiment. FIG. 19 is a cross-sectional view of a rotor of the fourth embodiment. FIG. 19 is a cross-sectional view of a rotor of the fourth embodiment. FIG. 19 is a diagram explaining a magnetic circuit formed in the rotor of the fourth embodiment. FIG. 19 is a diagram explaining evaluation results for the rotor member of the fourth embodiment. FIG. 19 is a cross-sectional view of a rotor of a comparative example. FIG. 19 is a diagram explaining evaluation results for the rotor of the fourth embodiment. FIG. 19 is a cross-sectional view of a motor including a rotor member of the fifth embodiment. FIG. 19 is a perspective view of a rotor member of the fifth embodiment. 31. A perspective view of a rotor according to a fifth embodiment. A diagram explaining evaluation results for a rotor member according to the fifth embodiment. A diagram schematically showing a cross section of a shaft portion according to a sixth embodiment. A diagram explaining evaluation results for a rotor member according to the sixth embodiment. A cross-sectional view of a rotor according to a seventh embodiment. A diagram explaining evaluation results for a rotor according to the seventh embodiment. A cross-sectional view of an axial gap motor according to an eighth embodiment. A cross-sectional view taken along line B-B in FIG. 31. A diagram explaining evaluation results for a rotor according to the eighth embodiment. A cross-sectional view of an axial gap motor according to a ninth embodiment. A cross-sectional view of a rotor including a rotor according to a tenth embodiment. A cross-sectional view of a first modified example of a rotor member according to the first embodiment. A cross-sectional view of a second modified example of a rotor member according to the first embodiment.

[0028] <First embodiment> Figure 1 is a cross-sectional view of a motor including a rotor member according to the first embodiment. A rotor member 100 according to the present embodiment is used in a motor 1A that outputs rotational torque when supplied with electric power. The motor 1A 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 C1A of the motor 1A and is rotatable about the central axis C1A.

[0029] Fig. 2 is a perspective view of the 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.

[0030] 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 generally cylindrical rotor core portion 110. 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.

[0031] The shaft portion 120 has two shaft portions 121 and 122. Each of the two shaft portions 121 and 122 is formed so as to protrude from each of two end faces 113 and 114 of the rotor core portion 110, which has a substantially cylindrical shape (see FIG. 1). Each of the shaft portions 121 and 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 and 122 is smaller than the outer diameter of the rotor core portion 110. The end of each of the shaft portions 121 and 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.

[0032] 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 method first involves preparing an axial measurement sample from the shaft portion 120, measuring 2 mm in the axial direction and 10 mm x 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 x 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 by 2 W / (m·K) or more than the thermal conductivity in the direction perpendicular to the axial direction. This makes it easier for the shaft portion 120 to dissipate heat from the rotor core portion 110 to the outside of the motor 1A. Note that the thermal conductivity in the axial direction of the shaft portion 120 may be less than the thermal conductivity in the direction perpendicular to the axial direction by more than 2 W / (m·K).

[0033] 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 alumina (Al ２ O ３ ), silica (SiO ２ ), titanium oxide (TiO ２ ), zirconia (ZrO ２ ), oxide ceramics such as magnesia (MgO), silicon carbide (SiC), boron carbide (B ４ Carbide ceramics such as titanium carbide (TiC), chromium carbide (CrC), and aluminum nitride (AlN), silicon nitride (Si ３ N ４The rotor member 100 is formed of at least one of nitride ceramics such as silicon nitride, 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 spectroscopy (EDS). The rotor member 100 of this embodiment is formed of silicon nitride.

[0034] The ceramic forming the rotor member 100 of this embodiment has an average crystal grain size of 5.0 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, the measurement method involves first setting multiple square measurement ranges (e.g., three to five) with sides of 500 μm on the surface or cross section of the rotor member 100. Next, the number of particles present on the diagonal of each 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 of 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 (SEM). In a specific measurement method, 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 area of ​​the areas corresponding to pores is calculated, and the porosity is calculated by calculating the ratio of the area to the area of ​​the entire SEM image. Note that the average grain size of the ceramic crystal grains forming the rotor member 100 may be greater than 5.0 μm, and the porosity may be greater than 3%.

[0035] 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 1A 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. Note that 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.

[0036] 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 (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.

[0037] The windings 220 are conductor wires covered with an insulator, and are wound around each of the plurality of protrusions 211 of the stator core 210. When electricity supplied from outside the motor 1A flows through the windings 220, the windings 220 generate a magnetic field.

[0038] 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.

[0039] Next, a method for manufacturing the rotor member 100 of this embodiment will be described. As an example of a method for manufacturing the rotor member 100, first, predetermined amounts of ceramic particles and a sintering aid are weighed as main raw materials. In this embodiment, when weighing the ceramic particles, 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 milled 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 weighed first 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.

[0040] 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 fabricated, 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."

[0041] 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 produced 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 have the composition of the "material" shown in FIG. 5. Sample 11 was produced by stacking multiple electromagnetic steel sheets. Sample 12 was produced by extruding and processing epoxy resin. Note that ZrB ２ and TiB ２ and the volume ratio of Al in sample 6 ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0042] The "average grain size" shown in FIG. 5 indicates 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 indicates 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 pores in the binarized SEM image). The "thermal conductivity difference" shown in FIG. 5 indicates 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).

[0043] 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 "SPM 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.

[0044] The "temperature" shown in Figure 5 indicates the resistance of the rotor members to temperature rise. The "temperature" was measured using the following method. First, the temperature of the rotor members of the motors equipped with each of Samples 1 to 11 and the SPM motor of the comparative example was measured after rotating at 7,500 rpm for one hour. Next, the degree of the magnitude of the temperature measured for each of Samples 1 to 11 relative to the temperature of the rotor member of the SPM motor of the comparative example was taken as the "temperature" and classified into the following symbols: S: Lower than the SPM motor of the comparative example by more than 20°C A: Lower than the SPM motor of the comparative example by more than 10°C and up to 20°C B: Lower than the SPM motor of the comparative example to 10°C or less C: Temperature similar to that of the SPM motor of the comparative example

[0045] The "rotational efficiency" shown in Figure 5 indicates the ratio of output to input in the motor, i.e., the efficiency of the motor. The "rotational efficiency" in this evaluation test was measured using the following method. First, the output torque of the motors equipped with each of Samples 1 to 11 and the SPM motor of the comparative example was measured after rotating at 7,500 rpm for one hour. Next, the ratio of the magnitude of the output torque measured in the motors equipped with each of Samples 1 to 11 to the output torque measured in the SPM motor of the comparative example was defined as "rotational efficiency" and classified into the following symbols: S, A, B, and C. S: Improved by 11% or more compared to the SPM motor of the comparative example. A: Improved by 6% or more but less than 11% compared to the SPM motor of the comparative example. B: Improved by less than 6% compared to the SPM motor of the comparative example. C: Similar to the SPM motor of the comparative example.

[0046] 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 be rotated at 10,000 rpm or more without breaking was measured. Next, the length of time that the motors could be rotated was determined as "strength" and classified into the following symbols A, B, and C. A: Rotation for 1 hour or more B: Rotation for 10 minutes or more but less than 1 hour C: Rotation for less than 10 minutes

[0047] In the "temperature" graph shown in Figure 5, Samples 1 to 10, which are made of ceramic, were confirmed to exhibit superior performance compared to Sample 11, which is made of electromagnetic steel sheet. Sample 11, which is made of electromagnetic 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 prone to iron loss. This suppresses heat generation in the rotor components, making Samples 1 to 10 less prone 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 portion, heat from the rotor core portion moves along the axial direction of the shaft portion and is easily dissipated from the shaft portion.

[0048] 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 forming Sample 11 has a larger thermal expansion coefficient than the ceramic forming 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 smaller thermal expansion coefficient, so their shape changes less with temperature rise, and an increase in mechanical loss is suppressed. Therefore, it is thought that the "rotational efficiency" is improved because the decrease in output torque is suppressed compared to the SPM motor of the comparative example.

[0049] Furthermore, among Samples 1 to 10, Samples 4 to 10, in which the ceramic material forming the rotor members 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 members. This is thought to enable an improvement in the output torque of the motor.

[0050] In terms of "strength" shown in Figure 5, it was confirmed that Samples 1 to 10, which are made of ceramic, exhibit 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 crystal grains forming the rotor member have an "average grain size" of 5.0 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 crystal grains have an "average grain size" of greater than 5.0 μm and a "porosity" of greater than 3%. In other words, it was confirmed that the strength of the rotor member is improved when the ceramic crystal grains forming the rotor member have an "average grain size" of 5.0 μm or less and a "porosity" of 3% or less.

[0051] 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, among ceramics, oxides, carbides, and nitrides have higher strength than borides. As a result, motors equipped with Samples 4 to 10 can rotate at higher speeds.

[0052] Next, an evaluation test of the rotor of this embodiment will be described. In this evaluation test, five types of motors (hereinafter referred to as "samples") were fabricated, each differing in one of the following: rotor material, rotor structure, the presence or absence of a magnetic part or the material, and motor structure, and the five samples were evaluated for "iron loss" and "rotational efficiency."

[0053] FIG. 7 is a diagram illustrating the evaluation results for the rotor of this embodiment. Of the five types of samples used in this evaluation test, Samples 13 to 15 are motors equipped with rotors manufactured using a method similar to the manufacturing method for rotor 10 of this embodiment. For each of Samples 13 to 15, the ceramic particle material used as the main raw material was selected so that the rotor core and shaft had the composition of the "material" of the "rotor" shown in FIG. 7. Sample 16 is a motor equipped with a rotor manufactured by stacking multiple electromagnetic steel plates. Sample 17 is a motor equipped with a rotor manufactured by extruding and processing epoxy resin.

[0054] The "structure" of the "rotor" shown in Figure 7 indicates, for each of Samples 13 to 17, whether the rotor core and shaft are formed separately ("split") or integrally ("integrated"). The "magnetic portion" shown in Figure 7 indicates, for each of Samples 13 to 17, whether or not a magnetic portion is provided in the rotor core. Samples 13 to 17 do not have a magnetic portion.

[0055] 7 shows the structure of the sample. Each of Samples 13 to 15, whose rotors are made of ceramic, is an SPM, which has the same structure as the motor 1A of this embodiment.

[0056] The "iron loss" and "rotation efficiency" shown in FIG. 7 each represent the results of a comparison with the comparative SPM motor equipped with the comparative rotor 90 shown in FIG. 6 . 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 Samples 13 to 17 and the comparative SPM motor. The iron loss of each motor was then 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 values ​​of each motor, the magnitude of the iron loss of Samples 13 to 17 relative to the comparative SPM motor was designated as the "iron loss" for each of Samples 13 to 17, and the magnitude of the "iron loss" was classified into the following symbols, A and B. A: 95% or more but less than 100% of the SPM motor of the comparative example B: Less than 95% of the SPM motor of the comparative example

[0057] The "rotational efficiency" shown in Figure 7 indicates the ratio of output to input in the motor, i.e., the efficiency of the motor. In this evaluation test, the "rotational efficiency" was first measured for Samples 13 to 17 and the SPM motor of the comparative example, when rotated at a predetermined rotation speed. The degree of the magnitude of the output measured for the motors equipped with Samples 13 to 17 relative to the output measured for the SPM motor of the comparative example was taken as the "rotational efficiency" and classified into the following symbols A, B, and C: A: Improved by 1% or more compared to the SPM motor of the comparative example B: Same as the SPM motor of the comparative example, or improved by less than 1% C: Decreased compared to the SPM motor of the comparative example

[0058] In the "iron loss" analysis shown in Figure 7, it was confirmed that Samples 13 to 15, whose rotors were made of ceramic, exhibited superior performance to Sample 16, whose rotor was made of electromagnetic steel sheet. Sample 16, whose rotor core and shaft were both made of electromagnetic steel sheet, was prone to iron loss, such as hysteresis loss and eddy current loss. On the other hand, Samples 13 to 15, whose rotor core and shaft were both made of ceramic, were less likely to exhibit these losses. This suppresses heat generation in the rotor, making Samples 13 to 15 less susceptible to temperature rise. Therefore, it is possible to suppress a decrease in motor efficiency due to temperature rise. In the "rotation efficiency" analysis shown in Figure 7, it was confirmed that Samples 13 to 15, whose rotors were made of ceramic, exhibited superior performance to Sample 17, whose rotor was made of epoxy resin, and exhibited performance comparable to or better than Sample 16, whose rotor was made of electromagnetic steel sheet.

[0059] According to the rotor member 100 of this embodiment described above, the rotor member 100 is formed from ceramic, which allows for smaller iron loss in the rotor member 100 than in electromagnetic steel sheets, iron, and the like. This makes it possible to suppress temperature increases 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 increases, 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, thereby suppressing increases in mechanical loss in the rotor member 100. This makes it possible to suppress temperature increases in the rotor member 100 due to frictional heat.

[0060] 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 1A.

[0061] 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 1A.

[0062] 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.

[0063] Furthermore, according to the rotor member 100 of this embodiment, the average crystal grain size of the ceramic forming the rotor member 100 is 5.0 μm or less, and the porosity is 3% or less, which gives the rotor member 100 a relatively high strength, thereby making it possible to suppress breakage due to stress generated when the rotor member 100 rotates.

[0064] 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.

[0065] Furthermore, according to the rotor 10 of this embodiment, the rotor core 110 and the shaft 120 of the rotor 10 are formed from ceramic, which allows for smaller iron loss in the rotor core 110 and other components than that of electromagnetic steel sheets or iron. Furthermore, the ceramic that forms the shaft 120 has a smaller thermal expansion coefficient than metal, which reduces changes in size of the shaft 120 due to temperature changes. This reduces the amount of change in friction between the shaft 120 and the bearings 310 and 320 that rotatably support the shaft 120, even if the temperature of the shaft 120 changes. Therefore, it is possible to suppress increases in mechanical loss in the rotor 10 due to temperature changes.

[0066] Furthermore, according to the motor 1A of this embodiment, the motor 1A 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 1A.

[0067] <Second embodiment> Fig. 8 is a cross-sectional view of a motor including a rotor member of a second embodiment. Fig. 9 is a perspective view of the rotor member of this embodiment. Fig. 10 is a perspective view of the rotor of this embodiment. The rotor member included in the rotor of the second embodiment is different from the rotor member of the first embodiment (Fig. 1) in the shape of the portion where the rotor core portion and the shaft portion of the rotor member are connected.

[0068] The rotor member 100 of this embodiment is used in a motor 1B that outputs rotational torque when supplied with electric power. The motor 1B 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 C1B of the motor 1B and is rotatable about the central axis C1B. In the rotor member 100 of this embodiment, the rotor core portion 110 and the shaft portion 120 are formed as a single ceramic member.

[0069] The rotor member 100 of this embodiment has a thermal expansion coefficient of 6.0×10 －６ / K or less, and the specific gravity is 5.0 g / cm ３ The rotor member 100 of this embodiment has a thermal expansion coefficient of 3.3×10 －６ / K and the specific gravity is 3.2 / cm ３ Silicon nitride (Si ３ N ４). Silicon nitride has a relatively small coefficient of thermal expansion, so its shape does not change significantly even when the temperature rises. This prevents friction with the bearings 310 and 320 (described later) from increasing even when the rotor member 100 rotates at high speed and the temperature rises. In other words, the rotor member 100 can prevent an increase in mechanical loss, particularly due to high-speed rotation. The thermal expansion coefficient of the rotor member 100 is measured using a thermomechanical analyzer (TMA) (measurement sample size: 3 mm x 3 mm x 10 mm). Furthermore, silicon nitride has a relatively small specific gravity, so the rotor member 100 can be rotated with a relatively small force. This allows the power required to rotate the rotor member 100 at high speed to be relatively small. The specific gravity of the rotor member 100 is measured using the Archimedes method. The ceramic forming the rotor member 100 of this embodiment is alumina (Al ２ O ３ ), silica (SiO ２ ), titanium oxide (TiO ２ ), zirconia (ZrO ２ ), oxide ceramics such as magnesia (MgO), silicon carbide (SiC), boron carbide (B ４ The rotor member 100 may be made of at least one of carbide ceramics such as titanium carbide (TiC), titanium carbide (TiC), and chromium carbide (CrC), and nitride ceramics such as aluminum nitride (AlN), titanium nitride (TiN), and sialon (SiAlON). The rotor member 100 may be made of, for example, a mixture of alumina and zirconia. The thermal expansion coefficient of the rotor member 100 is 3.0×10 －６ / K or more, and the specific gravity of the rotor member 100 is 3.0 g / cm ３ The above is desirable.

[0070] 11 is an enlarged view of portion A in FIG. 8 and is a partially enlarged view of the cross section of the rotor member 100. In the rotor member 100 of this embodiment, a connection portion P10 having an R-shaped outer surface P10a is provided at the boundary between the rotor core portion 110 and the shaft portion 120. In the rotor member 100 of this embodiment, the connection portion P10 between the rotor core portion 110 and the shaft portion 120 is formed to have an R-shape (curved surface shape) with a curvature radius R of 0.2 mm or more. Specifically, in the cross section of the rotor 10 shown in FIG. 11 , the contour line of the end face 113 of the rotor core portion 110 and the contour line of the side surface 121a of the shaft portion 121 are smoothly connected by the contour line of the outer surface P10a of the connection portion P10. In this embodiment, the contour line of the outer surface P10a of the connection portion P10 has a concave shape recessed toward the inside of the rotor member 100 and has the same shape as the arc of an imaginary circle VC10 having a radius R10 of 0.2 mm or more and 1.0 mm or less. Therefore, the center C10 of the imaginary circle VC10 is located outside the cross section of the rotor member 100 in the cross section of FIG. 11 . In this manner, in the rotor member 100 of this embodiment, the connection portion between the rotor core portion 110 and the shaft portion 121 has the shape shown in FIG. 11 , so that stress generated in the rotor member 100 is less likely to concentrate at the connection portion P10. This can prevent damage to the rotor member 100. Note that while FIG. 11 describes the connection portion P10 between the rotor core portion 110 and the shaft portion 121, the connection portion between the rotor core portion 110 and the shaft portion 122 has a similar shape. The magnitude of the R of the R-shape at the connection portion P10 is calculated by averaging the values ​​at three cross sections.

[0071] Next, an example of a manufacturing method for the rotor member 100 according to 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 a slurry is prepared by grinding and mixing for a predetermined period of time. Next, the prepared slurry is extrusion-molded to form an extruded body having a generally columnar shape. Next, the extruded body is processed to form a portion that will become the shaft portion 120, a portion that will become the support portion 111, and the like, to prepare a processed molded body having the shape of the rotor member 100. In this embodiment, when preparing the processed molded body, the outer surface P10a of the connection portion P10 between the rotor core portion 110 and the shaft portion 120 is formed to have a radius of 0.2 mm or more. Finally, the processed molded body is fired by heating under predetermined conditions to produce the ceramic rotor member 100. The manufacturing method of the rotor member 100 shown here is an example, and the manufacturing method is not limited to this.

[0072] 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 fabricated, differing in any of the rotor member material, thermal expansion coefficient, specific gravity, R-shape size, presence or absence of magnetic parts, or material, and each of the 12 samples was evaluated for "rotation efficiency," "rotatability," and "strength."

[0073] FIG. 12 is a diagram illustrating the evaluation results for the rotor member of this embodiment. Of the 12 types of samples used in this evaluation test, Samples 18 to 27 were produced by a method similar to the manufacturing method for the rotor member 100 of this embodiment. For each of Samples 18 to 27, 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. Sample 11 was produced by stacking multiple electromagnetic steel sheets, and is the same as Sample 11 used in the evaluation test of the first embodiment. Sample 12 was produced by extruding and processing epoxy resin, and is the same as Sample 12 used in the evaluation test of the first embodiment. Note that the Al in Sample 21 ２ O ３ and ZrO ２ and the volume ratio of Si in sample 22 ３ N ４ The volume ratio of TiN to Al was 7:3 in both cases.

[0074] The "thermal expansion coefficient" and "specific gravity" shown in FIG. 12 indicate the thermal expansion coefficient and specific gravity of the "material" forming each of Samples 18 to 27 and Sample 12. The thermal expansion coefficient of the samples was measured by TMA using samples measuring 3 mm × 3 mm × 10 mm, similar to the method for measuring the thermal expansion coefficient of the rotor member 100 of this embodiment. The specific gravity of the samples was measured using the Archimedes method, similar to the method for measuring the specific gravity of the rotor member 100 of this embodiment. "R" shown in FIG. 12 indicates the R value of the R shape of the connection between the rotor core portion and the shaft portion for each of Samples 18 to 27 and Samples 11 and 12. "R" shown in FIG. 12 indicates the processing value when each of Samples 18 to 27 and Samples 11 and 12 was manufactured.

[0075] The "magnetic portion" shown in Fig. 12 indicates whether or not a magnetic portion that forms a magnetic circuit is provided in the rotor core portion for each of Samples 18 to 27. As shown in Fig. 12, each of Samples 18 to 27 does not have a magnetic portion.

[0076] The "rotational efficiency" and "rotational performance" shown in FIG. 12 each represent the results of a comparison with the comparative SPM motor equipped with the comparative rotor member 900 shown in FIG. 6. The "rotational efficiency" shown in FIG. 12 indicates the ratio of output to input in the motor, i.e., the efficiency of the motor. The "rotational efficiency" was measured using the following method. First, the power required to maintain rotation at 3000 rpm was measured for motors equipped with Samples 18 to 27, Samples 11 and 12, and the comparative SPM motor. Next, the ratio (ΔE) of the magnitude of the power measured for the motors equipped with Samples 18 to 27, Samples 11 and 12 to the power measured for the comparative SPM motor was defined as the "rotational efficiency" and classified into the following symbols A, B, and C. A: 6%≦ΔE<11% (improved by 6% or more and less than 10% compared to the SPM motor of the comparative example) B: ΔE>6% (improved by less than 6% compared to the SPM motor of the comparative example) C: ΔE was almost 0% (similar to the SPM motor of the comparative example)

[0077] "Rotational performance" shown in Figure 12 indicates the ease of rotation of the rotor member. "Rotational performance" was measured using the following method. First, the magnitude of the external force required to rotate samples 18 to 27, samples 11 and 12, and the comparative rotor member 900, which did not have magnets mounted, at 10,000 rpm or more was measured. Next, the magnitude of the external force required to rotate the rotor member was defined as "rotational performance" and classified into the following symbols A, B, and C. A: Rotation possible with 95% or less of the external force required for the SPM motor of the comparative example. B: Rotation possible with 95% or more but less than 99% of the external force required for the SPM motor of the comparative example. C: External force equivalent to that required for the SPM motor of the comparative example is required.

[0078] The "strength" shown in Figure 12 was measured by the following method. First, the rotation speed was gradually increased for motors equipped with Samples 18 to 27 and Samples 11 and 12, and the rotation speed at which the rotor member broke was measured. Next, the magnitude of the rotation speed was taken as "strength" and classified into the following symbols A, B, and C. A: The rotation speed at which fracture occurred was 10,001 rpm or more. B: The rotation speed at which fracture occurred was 5,001 rpm or more and 10,000 rpm or less. C: The rotation speed at which fracture occurred was 5,000 rpm or less.

[0079] The "rotational efficiency" shown in Figure 12 confirmed that Samples 18 to 27, which are made of ceramic, exhibited superior performance to Sample 11, which is made of electromagnetic steel sheet. The electromagnetic steel sheet forming Sample 11 has a larger thermal expansion coefficient than the ceramic forming Samples 18 to 27. As a result, Sample 11 is prone to experiencing increased mechanical loss, such as friction between the bearing and shaft, as the temperature rises. On the other hand, Samples 18 to 27, which are made of ceramic, have a smaller thermal expansion coefficient, so they can suppress increases in mechanical loss even when the temperature rises. As a result, motors equipped with Samples 18 to 27 have less output loss due to friction and can maintain a predetermined rotation speed with less power.

[0080] Furthermore, among Samples 18 to 27, the thermal expansion coefficient was 6.0 × 10 －６ / K or less, and Samples 22 to 27 have a thermal expansion coefficient of 6.0 × 10 －６ It was confirmed that the samples exhibited superior performance in terms of "rotation efficiency" compared to Samples 19 to 21, which had a thermal expansion coefficient of 6.0 × 10 －６ / K or less, the increase in mechanical loss due to temperature rise can be further suppressed. As a result, the motors equipped with Sample 18 and Samples 22 to 27 can maintain a predetermined rotation speed with even less power.

[0081] In terms of "rotational performance" shown in Figure 12, it was confirmed that Samples 18 to 27, which are made of ceramic, exhibited superior performance to Sample 11, which is made of electromagnetic steel sheet. The electromagnetic steel sheet forming Sample 11 has a greater specific gravity than the ceramic forming Samples 18 to 27. Therefore, a greater external force is required to rotate Sample 11 at a predetermined rotation speed. On the other hand, the specific gravity of the ceramic forming Samples 18 to 27 is relatively small, so a small external force is required to rotate Sample 11 at a predetermined rotation speed.

[0082] In addition, among Samples 18 to 27, the specific gravity was 5.0 g / cm ３ Sample 19 and samples 21 to 27, which have a specific gravity of 5.0 g / cm or less, ３ It was confirmed that the sample exhibited superior performance in terms of "rotation" compared to the larger samples 18 and 20. ３ Below this value, the external force required to rotate at a constant rotation speed becomes even smaller. As a result, the motors equipped with Sample 19 and Samples 21 to 27 can rotate at a predetermined rotation speed with even smaller external force.

[0083] In terms of "strength" shown in Figure 12, it was confirmed that Samples 18 to 27, which are made of ceramic, exhibited superior performance to Sample 12, which is made of epoxy resin. Furthermore, among Samples 18 to 27, Samples 26 and 27, which have an "R" of 0.2 mm or more, exhibited superior "strength" performance to Samples 18 to 25, which have an "R" of less than 0.2 mm. This is because, at the connection between the rotor core and shaft, the R shape is 0.2 mm or more, which makes it difficult for stress generated in the rotor members to concentrate at the connection.

[0084] According to the rotor member 100 of this embodiment described above, the rotor member 100 is formed from ceramic, which allows for smaller iron loss in the rotor member 100 than in electromagnetic steel sheets, iron, and the like. This makes it possible to suppress temperature increases 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 increases, 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, thereby suppressing increases in mechanical loss in the rotor member 100. This makes it possible to suppress temperature increases in the rotor member 100 due to frictional heat.

[0085] Furthermore, according to the rotor member 100 of this embodiment, the rotor core portion 110 and the shaft portion 120 included in the rotor member 100 are each formed from ceramic. This reduces iron loss generated in the rotor member 100 and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, because the rotor core portion 110 and the shaft portion 120 are formed from a single ceramic member, heat generated in the rotor core portion 110 is easily conducted to the shaft portion 120. This makes it easier for heat generated in the rotor core portion 110 to be released to the outside of the motor 1B via the shaft portion 120, thereby suppressing a temperature rise in the rotor member 100.

[0086] Furthermore, according to the rotor member 100 of this embodiment, since the rotor member 100 has a relatively small coefficient of thermal expansion, an increase in mechanical loss can be suppressed even when the temperature rises. This reduces output loss due to friction. Furthermore, since the specific gravity of the rotor member 100 is relatively small, it can be rotated with a relatively small force. Therefore, the electric power required to rotate the rotor member 100 at a predetermined rotation speed can be relatively small.

[0087] Furthermore, according to the rotor member 100 of this embodiment, the connection portion between the rotor core portion 110 and the shaft portion 120 formed to protrude from the end face of the rotor core portion 110 is formed to have an R shape with an R of 0.2 mm or more. This makes it difficult for stress generated in the rotor member 100 to concentrate at the connection portion, thereby preventing damage to the rotor member 100.

[0088] 13 is a diagram schematically illustrating a cross section of a shaft portion of a third embodiment. The rotor member included in the rotor of the third embodiment has a different configuration of the shaft portion compared to the rotor member of the first embodiment (FIG. 1).

[0089] The rotor member 100 of this embodiment is used in a motor that outputs rotational torque when power is supplied. The motor of this embodiment includes a rotor 10 having the rotor member 100, a stator 20, and a motor case 30. The rotor 10 is provided on the central axis of the motor of this embodiment so as to be rotatable about the central axis.

[0090] In this embodiment, the shaft portion 120 of the rotor member 100 has a surface roughness Ra of 15 μm or less. The ends of each of the shaft portions 121 and 122 opposite to the side connected to the rotor core portion 110 are rotatably supported by two bearings 310 and 320, which will be described later. As a result, friction between each of the shaft portions 121 and 122 and the bearings 310 and 320 is relatively small, making it easier for the rotor 10 to rotate relative to the stator 20 and enabling it to rotate at higher speeds. The ends of each of the shaft portions 121 and 122 opposite to the side connected to the rotor core portion 110 are exposed to the outside of the motor case 30.

[0091] 13 is a schematic diagram of a cross section of the shaft portion 120. It is a schematic diagram of an SEM image of the cross section of the shaft portion 120 exposed by etching, captured by a scanning electron microscope. The shaft portion 120 of this embodiment has a plurality of crystal grains 120a and a grain boundary liquid phase 120b surrounded by the crystal grains 120a. In this embodiment, the area ratio of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 is less than 10% (i.e., the area ratio of the crystal grains 120a in the cross section of the shaft portion 120 is 90% or more). When the area ratio of the grain boundary liquid phase in the cross section is less than 10%, as in the shaft portion 120 of this embodiment, the crystal grains are in contact with each other in a relatively large area, which facilitates heat transfer. Alternatively, the thickness of the grain boundary liquid phase, which conducts heat less easily than the crystal grains, does not exceed a certain thickness, which makes it less likely to impede heat transfer. As a result, the shaft portion 120 of this embodiment has a structure that allows heat to be easily transmitted. The proportion of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 is calculated using analysis results obtained by energy dispersive X-ray analysis (EDS) of the cross section of the shaft portion 120 as shown in FIG. 13. Specifically, for example, in a square analysis area with sides of 100 μm, the analysis results of the energy dispersive X-ray analysis are subjected to image processing to classify the area into areas representing crystal grains 120a and black areas representing the grain boundary liquid phase 120b, and the proportion of the area occupied by the grain boundary liquid phase 120b in the analysis area is calculated. Note that the proportion of the area occupied by the grain boundary liquid phase 120b in the cross section of the shaft portion 120 is 0% or more in terms of area ratio.

[0092] In this embodiment, the average grain size of the crystal grains 120a in the shaft portion 120 is 5.0 μm or less. In this embodiment, the average grain size of the crystal grains 120a in the shaft portion 120 is measured using the linear intercept method. Specifically, the measurement method involves first setting multiple square measurement ranges (e.g., three to five measurement ranges) with sides of 500 μm on a cross section of the shaft portion 120. Next, the number of particles present on the diagonal of each 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 grain size of the crystal grains in each measurement range. Finally, the average grain size of the crystal grains in the shaft portion 120 is calculated using the average grain size of the crystal grains calculated for each measurement range. The average grain size of the crystal grains in the shaft portion 120 is, for example, 0.5 μm or more.

[0093] Next, an example of a method for manufacturing the rotor member 100 of this embodiment will be described. In the method for manufacturing the rotor member 100, first, predetermined amounts of ceramic particles and a sintering aid are weighed out as main raw materials. In the rotor member 100 of this embodiment, the area ratio of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 can be adjusted by adjusting the amount of the sintering aid to be weighed out. For example, Y ２ O ３ , Nd ２ O ３ , SiO ２By adding approximately 3 to 15 wt % of SiC, AlN, or the like, the area ratio of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 is reduced. Furthermore, in the rotor member 100 of this embodiment, the average grain size of the crystal grains 120a in the shaft portion 120 can be set to 5.0 μm or less by adjusting the average grain size of the ceramic grains and the firing temperature of the processed green body (described below), as well as by controlling the grain size of the sintering aid and the dispersion state of the sintering aid in the slurry (described below). For example, by setting the average grain size of the ceramic grains as the main raw material to 1 to 3 μm or less, setting the firing temperature of the processed green body to 1650 to 1800°C, and then controlling the grain size of the sintering aid and the dispersion state of the sintering aid in the slurry, the average grain size of the crystal grains 120a in the shaft portion 120 can be set to 5.0 μm or less. Note that the methods for reducing the area ratio of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 and the methods for setting the average grain size of the crystal grains 120a in the shaft portion 120 to 5.0 μm or less are not limited to these.

[0094] Next, the weighed materials are placed in a ball mill together with ethanol and milled and mixed for a predetermined time to produce a slurry. The produced slurry is then extruded to form an extruded body having a generally cylindrical shape. The extruded body is then processed to form the shaft portion 120, the support portion 111, and other portions, to produce a processed body having the shape of the rotor member 100. The processed body is then fired by heating under predetermined conditions (e.g., a firing temperature in the range of 1650 to 1800°C) to produce a fired body. Finally, the surface of the portion of the fired body that will become the shaft portion 120 is polished to a surface roughness Ra of 15 μm or less. This completes the rotor member 100. Note that the manufacturing method for the rotor member 100 shown here is merely an example and is not limited to this manufacturing method. The surface roughness Ra of the portion that will become the shaft portion 120 is, for example, 1 μm or more.

[0095] Next, an evaluation test of the rotor member according to this embodiment will be described. In this evaluation test, 13 types of rotor members (hereinafter referred to as "samples") for use in SPM motors were fabricated, differing in any of the following: rotor member material, area ratio of grain boundary liquid phase, structure, average grain size, surface roughness, presence or absence of magnetic parts, or material, and each of the 13 samples was evaluated for "iron loss," "rotational strength," and "rotational efficiency."

[0096] FIG. 14 is a diagram illustrating the evaluation results of the rotor member of this embodiment. Of the 13 types of samples used in this evaluation test, Samples 28 to 37 and Sample 38 were manufactured by a method similar to the manufacturing method of the rotor member 100 of this embodiment. For each of Samples 28 to 37 and Sample 38, 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. 14. Sample 11 was manufactured by stacking multiple electromagnetic steel sheets, and is the same as Sample 11 used in the evaluation test of the first embodiment. Sample 12 was manufactured by extruding and processing epoxy resin, and is the same as Sample 12 used in the evaluation test of the first embodiment. Note that the Si content of Sample 32 ２ N ４ and TiN volume ratio, and Al in Samples 35 to 37 ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0097] The "area ratio of grain boundary liquid phase" shown in Figure 14 is a value indicating the area ratio of the grain boundary liquid phase in the cross section of the shaft portion for each of Samples 28 to 37 and Sample 38. The "area ratio of grain boundary liquid phase" was measured using a method similar to the method for calculating the proportion of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 in this embodiment. The "structure" shown in Figure 14 indicates the relationship between the rotor core portion and the shaft portion for each of Samples 28 to 37, Samples 11 and 12, and Sample 38.

[0098] The "average grain size" shown in FIG. 14 indicates the average grain size of the ceramic crystal grains forming each of Samples 28 to 37 and Sample 38. The "average grain size" was measured using a method similar to the linear intercept method for measuring the average grain size of the rotor member 100 of this embodiment. The "surface roughness" shown in FIG. 14 indicates the surface roughness Ra of the shaft portion for each of Samples 28 to 38 and Samples 11 and 12. The surface roughness Ra of the shaft portion was measured using a stylus-type surface roughness tester as specified in JIS B0633:2001. The "magnetic portion" shown in FIG. 14 indicates whether or not a magnetic portion is provided in the rotor core for each of Samples 28 to 37, and if a magnetic portion is provided, the material of that magnetic portion. None of Samples 28 to 37 has a magnetic portion.

[0099] The "iron loss" and "rotation efficiency" shown in FIG. 14 represent the results of a comparison with the comparative SPM motor equipped with the comparative rotor member 900 shown in FIG. 6 . The "iron loss" shown in FIG. 14 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 the motors equipped with Samples 28 to 37, Samples 11 and 12, and Sample 38, as well as the comparative SPM motor. The loss of each motor was then 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. The calculated loss values ​​of each motor were classified into the following symbols A and B based on the magnitude of the iron loss of Samples 28 to 37, Samples 11 and 12, and Sample 38 compared to the comparative SPM motor. A: Less than 95% of the SPM motor of the comparative example B: 95% or more of the SPM motor of the comparative example

[0100] The "rotational strength" shown in Figure 14 indicates the durability of the rotor member against centrifugal force and stress acting during rotation. The "rotational strength" was measured using the following method. First, the rotation speed was gradually increased for motors equipped with each of Samples 28 to 37, Samples 11 and 12, and Sample 38, and the rotation speed at which the rotor member broke was measured. Next, the magnitude of the rotation speed was classified as "rotational strength" into the following symbols: S, A, B, and C. S: The rotation speed at which the rotor member broke was 15,000 rpm or more and less than 20,000 rpm. A: The rotation speed at which the rotor member broke was 10,000 rpm or more and less than 15,000 rpm. B: The rotation speed at which the rotor member broke was 5,000 rpm or more and less than 10,000 rpm. C: The rotation speed at which the rotor member broke was less than 5,000 rpm.

[0101] The "rotational efficiency" shown in Figure 14 indicates the ratio of output to input in the motor, i.e., the efficiency of the motor. For "rotational efficiency," first, the motor output when rotated at a predetermined rotation speed was measured for motors equipped with each of Samples 28 to 37, Samples 11, 12, and Sample 38, and the SPM motor of the comparative example. The degree of magnitude of the output measured for the motors equipped with each of Samples 28 to 37, Samples 11, 12, and Sample 38 relative to the output measured for the SPM motor of the comparative example was taken as "rotational efficiency" and classified into the following symbols A and B: A: Improvement of more than 1% compared to the SPM motor of the comparative example B: Improvement of 1% or less compared to the SPM motor of the comparative example

[0102] 14, it was confirmed that Samples 28 to 37 and Sample 38, which are made of ceramic, exhibit superior performance to Sample 11, which is made of electromagnetic steel sheet. Sample 11, which is made of electromagnetic steel sheet, is prone to iron loss such as hysteresis loss and eddy current loss, while Samples 28 to 37 and Sample 38, which are made of ceramic, are less likely to experience iron loss. This suppresses heat generation in the rotor components, and therefore Samples 28 to 37 and Sample 38 are less likely to experience temperature rise.

[0103] When comparing Samples 28 to 37, which are ceramic "materials," and Sample 38, in which Samples 28 to 37 have an "area ratio of grain boundary liquid phase" of less than 10%, with Sample 38, which has an "area ratio of grain boundary liquid phase" of 10%, differences in "rotational strength" were confirmed. Specifically, it was confirmed that Samples 28 to 37, which have an "area ratio of grain boundary liquid phase" of less than 10%, have greater strength than Sample 38, which has an "area ratio of grain boundary liquid phase" of 10%. As described above, when a ceramic member has an area ratio of grain boundary liquid phase of less than 10% in the cross section, the crystal grains are in contact with each other in a relatively large area, which facilitates heat transfer. Alternatively, the thickness of the grain boundary liquid phase, which conducts heat less easily than the crystal grains, does not exceed a certain thickness, which makes it less likely to impede heat transfer. Therefore, it is considered that Samples 28 to 37, in which the "area ratio of the grain boundary liquid phase" is less than 10%, have superior heat conductivity compared to Sample 38, in which the "area ratio of the grain boundary liquid phase" is 10%.

[0104] 14, it was confirmed that, among Samples 28 to 37, Samples 31 to 37, which had an "average particle size" of 5 μm or less, exhibited better performance than Samples 28 to 30, which had an "average particle size" of more than 5 μm. In addition, it was confirmed that, among Samples 31 to 37, which had an "average particle size" of 5 μm or less, Samples 35 to 37, which had an "average particle size" of 2 μm or less, exhibited even better performance than Samples 31 to 34, which had an "average particle size" of more than 2 μm but not more than 5 μm.

[0105] 14, it was confirmed that, among Samples 28 to 37, Samples 35 to 37, which have a surface roughness of 15 μm or less, exhibit superior performance to Samples 28 to 34, which have a surface roughness of more than 15 μm. This is thought to be because, as the surface roughness Ra of the shaft portion decreases, the frictional force between the rotor member and the bearing that rotatably supports the rotor member decreases, reducing loss due to frictional force in the input to the motor and resulting in greater output for the same input.

[0106] According to the rotor member 100 of this embodiment described above, the rotor member 100 is formed from ceramic, which allows for smaller iron loss in the rotor member 100 than in electromagnetic steel sheets, iron, and the like. This makes it possible to suppress temperature increases 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 increases, 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, thereby suppressing increases in mechanical loss in the rotor member 100. This makes it possible to suppress temperature increases in the rotor member 100 due to frictional heat.

[0107] Furthermore, according to the rotor member 100 of this embodiment, the rotor core portion 110 and the shaft portion 120 included in the rotor member 100 are each formed of ceramic. This reduces iron loss generated in the rotor member 100 and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, the proportion of the grain boundary liquid phase 120b in the cross section of the shaft portion 120 is less than 10% in terms of area ratio. This allows heat to be easily conducted in the shaft portion 120, making it easier to dissipate heat generated in the rotor core portion 110 to the outside of the motor via the shaft portion 120. Therefore, it is possible to suppress a temperature rise in the rotor member 100.

[0108] Furthermore, according to the rotor member 100 of this embodiment, the average grain size of the crystal grains in the shaft portion 120 is 5.0 μm or less, which gives the shaft portion 120 a relatively high strength, thereby making it possible to suppress breakage.

[0109] Furthermore, according to the rotor member 100 of this embodiment, the surface roughness Ra of the shaft portion 120 is relatively small, which reduces the frictional force between the portion that rotatably supports the shaft portion 120 and the shaft portion 120. This allows the rotor member 100 to rotate at a higher speed.

[0110] 15 is a cross-sectional view of a motor including a rotor member according to a fourth embodiment. The rotor member of the rotor according to the fourth embodiment differs from the rotor member of the first embodiment (FIG. 1) in that it includes a magnetic portion.

[0111] Similar to the rotor 10 of the first embodiment, the rotor 40 of the fourth embodiment is provided in a motor 1D 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 a central axis C1D of the motor 1D and is rotatable about the central axis C1D.

[0112] Fig. 16 is a perspective view of the rotor member of this embodiment. Fig. 17 is a perspective view of the rotor of this embodiment. Fig. 18 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 support portions 411 for supporting magnets 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.

[0113] As shown in FIG. 16 , 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 the present embodiment, the opening portion of the support portion 411 is formed to have an annular shape, and as shown in FIGS. 17 and 18 , 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 the present embodiment, a plurality of insertion holes 414 are formed so that one magnetic portion 440 is positioned across two adjacent magnets 430 among the plurality of magnets 430 supported by the support portion 411 (see FIG. 18 ).

[0114] The shaft portion 420 has two shaft portions 421, 422. Each of the two shaft portions 421, 422 is formed so as to protrude from each of two end faces 412, 413 of the rotor core portion 410, which has a substantially cylindrical shape (see FIG. 16 ). Each of the shaft portions 421, 422 has a substantially rod shape with its longitudinal direction aligned with the central axis C100 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.

[0115] The ceramic forming the rotor member 400 of this embodiment is at least one of oxide, carbide, and nitride, and has an average crystal grain size of 5.0 μm or less and a porosity of 3% or less. In the rotor member 400, the axial thermal conductivity of the shaft portions 421 and 422 is greater than the thermal conductivity in a direction perpendicular to the axial direction by 2 W / (m·K) or more. The rotor member 400 of this embodiment is formed of silicon nitride. The crystal grains of the ceramic forming the rotor member 400 may have an average grain size greater than 5.0 μm and a porosity greater than 3%. The axial thermal conductivity of the shaft portion 120 may be less than the thermal conductivity in a direction perpendicular to the axial direction by 2 W / (m·K). The rotor core portion 410 and the shaft portion 420 of this embodiment may be formed of a mixture of silicon nitride and titanium nitride. The thermal conductivity of the shaft portion 420 in the axial direction may be less than the thermal conductivity in a direction perpendicular to the axial direction by 2 W / (m·K).

[0116] The magnets 430 are supported by support portions 411 of the rotor core portion 410. In this embodiment, the ten magnets 430 are arranged inside 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 1D of this embodiment is a so-called IPM motor in which the magnets 430 are mounted inside the rotor core portion 410. Note that 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.

[0117] The magnetic portion 440 is provided in the rotor core portion 410 and is made of metal or soft magnetic ceramic. Materials for forming the magnetic portion 440 include iron (Fe), cobalt (Co), nickel (Ni), nanocrystalline soft magnetic material having nano-sized crystals in an amorphous (non-crystalline) alloy, electromagnetic steel sheet, ferrite (Fe ２ O ３ The magnetic portions 440 of this embodiment are formed of an electromagnetic steel plate. The ten magnetic portions 440 are inserted into the ten insertion holes 414 of the rotor core 410, respectively.

[0118] Fig. 19 is a diagram illustrating a magnetic circuit formed in the rotor of this embodiment. For convenience of illustration, Fig. 19 shows only the cross section of the rotor 40 also shown in Fig. 18. In this embodiment, the magnet 430 forms a magnetic circuit Mgc that passes through the magnetic portion 440.

[0119] Next, a method for manufacturing the rotor member 400 of this embodiment will be described. One example of a method for manufacturing the rotor member 400 is a method similar to the method for manufacturing the rotor member 100 of the first embodiment. The method for manufacturing the rotor member 400 differs from the method for manufacturing the rotor member 100 in that a 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 method for manufacturing the rotor member 400 shown here is one example, and the method is not limited to this.

[0120] Next, a method for manufacturing the rotor 40 of this embodiment will be described. One example of a method for manufacturing the rotor 40 is a method similar to the method for manufacturing the rotor 10 of the first embodiment. The method for manufacturing the rotor 40 differs from the method for manufacturing the rotor 10 in that a molded extruded body is processed to form a portion that becomes the support portion 411 and a portion that becomes the insertion hole 414, thereby producing a processed molded body having the shape of the rotor member 400, and then a magnet 430 is inserted into the support portion 411 formed in the sintered molded body, and a magnetic portion 440 is inserted into the insertion hole 414. Note that the method for manufacturing the rotor 40 shown here is an example and is not limited to this manufacturing method.

[0121] 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.

[0122] 20 is a diagram illustrating the evaluation results for the rotor member of this embodiment. Each of Samples 39 to 43 used in this evaluation test was produced by a method similar to the manufacturing method for the rotor member 400 of this embodiment. For each of Samples 39 to 43, the material of the ceramic particles as the main raw material was selected so as to have the composition of the "material" shown in FIG. 20. Note that Al in Samples 39 to 41 ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0123] The "average grain size" shown in Fig. 20 is a value indicating the average grain size of the crystal grains of the ceramic forming each of Samples 39 to 43. The "porosity" shown in Fig. 20 is a value indicating the proportion of pores contained in the ceramic forming each of Samples 39 to 43. The "thermal conductivity difference" shown in Fig. 20 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 39 to 43. The "average grain size," "porosity," and "thermal conductivity difference" shown in Fig. 20 were measured using the same method as the method used in the evaluation test of the first embodiment.

[0124] The "magnetic portion" shown in Figure 20 indicates the material forming the magnetic portion provided in the rotor core for each of Samples 39 to 43. Sample 39 has a magnetic portion formed from ferrite, while Sample 40 has a magnetic portion formed from a nanocrystalline soft magnetic material. Each of Samples 41 to 43 has a magnetic portion formed from an electromagnetic steel sheet.

[0125] Fig. 21 is a cross-sectional view of a rotor of a comparative example. In this evaluation test, the "temperature" and "rotation efficiency" shown in Fig. 20 each show the results of a comparison with a motor including a rotor 95 of a comparative example (hereinafter simply referred to as the "IPM motor of the comparative example"). As shown in Fig. 21, 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.

[0126] As with the first embodiment, the "temperature" and "rotational efficiency" shown in Figure 20 were evaluated using the same threshold values ​​as in the first embodiment, with the comparative rotor member 950 or the comparative IPM motor as the evaluation standard. As a result, as shown in Figure 20, it was confirmed that, for "temperature," each of Samples 39 to 43, whose "material" was ceramic, exhibited superior performance (evaluated as "S") compared to the comparative IPM motor. Similarly to "temperature," it was also confirmed that, for "rotational efficiency," each of Samples 39 to 43 exhibited superior performance (evaluated as "S" or "A") compared to the comparative IPM motor.

[0127] As in the first embodiment, the "strength" shown in Fig. 20 was determined by measuring the time that the motors equipped with each of Samples 39 to 43 could be rotated at 10,000 rpm or more without breaking, and using the same threshold value as in the first embodiment. As a result, as shown in Fig. 20, it was confirmed that each of Samples 39 to 43 also exhibited excellent performance (evaluated as "A") in terms of "strength."

[0128] Next, an evaluation test of the rotor of this embodiment will be described. In this evaluation test, five types of samples were fabricated, each differing in one of the following: rotor material, rotor structure, magnetic portion material, and motor structure, and the five types of samples were evaluated for "iron loss" and "rotation efficiency."

[0129] 22 is a diagram illustrating the evaluation results for the rotor of this embodiment. Each of the five types of samples (samples 44 to 48) used in this evaluation test is a motor equipped with a rotor manufactured by a method similar to the manufacturing method for rotor 40 of this embodiment. For each of samples 44 to 48, the material of the ceramic particles as the main raw material was selected so that the rotor core and shaft would each have the composition of the "material" of the "rotor" shown in FIG. 22. Note that the Si ２ N ４ and TiN volume ratio, and Al in sample 48 ２ O ３ and ZrO ２The volume ratio of the two is 7:3 in both cases.

[0130] The "structure" of the "rotor" shown in FIG. 22 indicates either a structure in which the rotor core portion and the shaft portion are formed separately ("split") or a structure in which they are formed integrally ("integrated") for each of Samples 44 to 48. In each of Samples 44 to 48, the rotor core portion and the shaft portion are formed integrally. The "magnetic portion" shown in FIG. 22 indicates the material of the magnetic portion provided in the rotor core portion for each of Samples 44 to 48. Sample 44 has a magnetic portion formed from ferrite, while Sample 45 has a magnetic portion formed from a nanocrystalline soft magnetic material. Samples 46 to 48 have a magnetic portion formed from an electromagnetic steel sheet.

[0131] The "structure" of the "motor" shown in Fig. 22 indicates the structure of the sample. Each of Samples 44 to 48 has the same structure as the motor 1D of this embodiment, that is, an IPM.

[0132] In this evaluation test, the "iron loss" and "rotation efficiency" shown in FIG. 22 represent the results of a comparison with the comparative IPM motor shown in FIG. 21 . The "iron loss" and "rotation efficiency" shown in FIG. 22 were evaluated using the same threshold values ​​as in the first embodiment, with the comparative IPM motor as the evaluation standard. Regarding the "iron loss" shown in FIG. 22 , Samples 44 to 48, whose rotors are made of ceramic, demonstrated superior performance compared to the comparative IPM motor with a rotor 95 made of electromagnetic steel sheet. Samples 44 to 48, whose rotors are made of ceramic, are less susceptible to iron loss, such as hysteresis loss and eddy current loss, and heat generation in the rotor is suppressed, resulting in less temperature rise. Therefore, a decrease in motor efficiency due to temperature rise can be suppressed. Furthermore, because each of Samples 44 to 48 has a magnetic portion in the rotor core, the magnetic circuit formed by the magnet preferentially passes through the magnetic portion in the rotor core. As a result, each of Samples 44 to 48 exhibits even lower iron loss in the rotor core than the comparative IPM motor without a magnetic section, which is thought to suppress temperature rise in the rotor core and thus suppress performance degradation of the magnetic section due to temperature rise. Therefore, the inclusion of a magnetic section can further improve motor efficiency. The "Rotational Efficiency" shown in Figure 22 confirms that Samples 44 to 48, which use ceramic as the "Material," exhibit superior performance to the comparative IPM motor with a rotor made of electromagnetic steel sheet.

[0133] 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.

[0134] Furthermore, according to the rotor 40 of this embodiment, the rotor core 410 and the shaft 420 are made of ceramic, which allows for smaller iron loss in the rotor core 410 and other components than in electromagnetic steel sheets or iron. Furthermore, the ceramic that forms the shaft 420 has a smaller thermal expansion coefficient than metal, which reduces changes in size of the shaft 420 due to temperature changes. This reduces the amount of change in friction between the shaft 420 and the bearings 310 and 320 that rotatably support the shaft 420, even if the temperature of the shaft 420 changes. Therefore, increases in mechanical loss in the rotor 40 due to temperature changes can be suppressed.

[0135] Furthermore, according to the rotor 40 of this embodiment, the rotor core 410 is provided with a magnetic portion 440 through which the magnetic circuit Mgc formed by the magnets 430 passes. The rotor member 400 provided in the rotor core 410 has relatively small iron loss and mechanical loss, and therefore is less likely to increase in temperature. This also suppresses temperature increases in the magnetic portion 440 provided in the rotor core 410, making it possible to suppress performance degradation of the magnetic portion 440 due to temperature changes.

[0136] Fifth Embodiment Fig. 23 is a cross-sectional view of a motor including a rotor member according to a fifth embodiment. Fig. 24 is a perspective view of the rotor member according to this embodiment. Fig. 25 is a perspective view of the rotor according to this embodiment. The rotor member included in the rotor of the fifth embodiment differs from the rotor member of the fourth embodiment (Fig. 15) in the shape of the portion where the rotor core portion and the shaft portion are connected in the rotor member.

[0137] The rotor member 400 of this embodiment is used in a motor 1E that outputs rotational torque when supplied with electric power. The motor 1E includes a rotor 40 having the rotor member 400, a stator 20, and a motor case 30. The rotor 40 is provided on a central axis C1E of the motor 1E so as to be rotatable about the central axis C1E. In the rotor member 400 of this embodiment, the rotor core portion 410 and the shaft portion 420 are formed as a single ceramic member.

[0138] The rotor 40 includes a rotor member 400, a magnet 430, and a magnetic portion 440. The rotor member 400 includes a rotor core portion 410 formed of ceramic and having a support portion 411 for supporting the 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, similar to the rotor member 100 of the first embodiment, the rotor core portion 410 and the shaft portion 420 are formed of a single ceramic member. In the rotor member 400 of this embodiment, a connection portion P40 having an R-shaped outer surface P40a is provided at the boundary between the rotor core portion 410 and the shaft portion 420. In the rotor member 400 of this embodiment, the connection portion P40 between the rotor core portion 410 and the shaft portion 420 is formed to have an R-shape with an R of 0.2 mm or more.

[0139] The rotor member 400 of this embodiment has a thermal expansion coefficient of 6.0×10 －６ / K or less, and the specific gravity is 5.0 g / cm ３ The rotor member 400 of this embodiment is made of ceramic, for example, silicon nitride. The ceramic forming the rotor member 400 is at least one of oxide, carbide, and nitride. Specifically, the rotor member 400 is made of alumina (Al ２ O ３ ), silica (SiO ２ ), titanium oxide (TiO ２ ), zirconia (ZrO ２ ), oxide ceramics such as magnesia (MgO), silicon carbide (SiC), boron carbide (B ４ Carbide ceramics such as titanium carbide (TiC), chromium carbide (CrC), and aluminum nitride (AlN), silicon nitride (Si ３ N ４ The insulating layer is formed of at least one of nitride ceramics such as titanium nitride (TiN) and sialon (SiAlON).

[0140] 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 second embodiment. The manufacturing method for the rotor member 400 differs from the manufacturing method for the rotor member 100 in that a molded extruded body is machined to form a portion that will become the shaft portion 420, a portion that will become the support portion 411, an insertion hole 414 into which the magnetic portion 440 is inserted, and the like, to produce a processed molded body having the shape of the rotor member 400. In this embodiment, when producing the processed molded body, the outer surface P40a of the connection portion P40 between the rotor core portion 410 and the shaft portion 420 is formed to have an R shape with an R of 0.2 mm or more. Note that the manufacturing method for the rotor member 400 shown here is an example and is not limited to this manufacturing method.

[0141] 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 to be used in IPM motors were fabricated, and the five types of samples were evaluated for "rotation efficiency," "rotatability," and "strength" in the same manner as in the evaluation test of the first embodiment.

[0142] 26 is a diagram illustrating the evaluation results for the rotor member of this embodiment. Each of Samples 49 to 53 used in this evaluation test was produced by a method similar to the manufacturing method for rotor member 400 of this embodiment. For each of Samples 49 to 53, the material of the ceramic particles used as the main raw material was selected so as to achieve the composition of the "material" shown in FIG.

[0143] The "thermal expansion coefficient" and "specific gravity" shown in FIG. 26 indicate the thermal expansion coefficient and specific gravity of the "material" forming each of Samples 49 to 53. The "thermal expansion coefficient" and "specific gravity" were measured using the same method as the evaluation method used in the second embodiment. "R" shown in FIG. 26 indicates the processing value of the R shape of the connection between the rotor core portion and the shaft portion for each of Samples 49 to 53 when they were manufactured. For all of Samples 49 to 53 shown in FIG. 26, "R" is 0.4 mm.

[0144] 26 indicates the material forming the magnetic portion provided in the rotor core for each of Samples 49 to 53. Sample 49 has a magnetic portion formed from ferrite, while Sample 50 has a magnetic portion formed from a nanocrystalline soft magnetic material. Samples 51 to 53 each have a magnetic portion formed from an electromagnetic steel sheet.

[0145] In this evaluation test, the "rotational efficiency" and "rotational performance" shown in FIG. 26 each show the results of a comparison with the comparative IPM motor shown in FIG. 21. The "rotational efficiency" and "rotational performance" shown in FIG. 26 were evaluated using the comparative rotor member 950 provided in the comparative IPM motor or the comparative IPM motor as the evaluation standard, and were judged using the same threshold values ​​as in the second embodiment. As a result, as shown in FIG. 26, it was confirmed that each of Samples 49 to 53 exhibited superior performance (evaluated as "A") in terms of both "rotational efficiency" and "rotational performance" compared to the comparative rotor member 950 or an IPM motor provided with the comparative rotor member 950.

[0146] As in the second embodiment, the "strength" shown in Fig. 26 was determined by gradually increasing the rotation speed of the motors equipped with each of Samples 49 to 53, measuring the rotation speed at which the rotor member broke, and using the same threshold value as in the second embodiment. As a result, as shown in Fig. 26, it was confirmed that each of Samples 49 to 53 also exhibited excellent performance (evaluated as "A") in terms of "strength."

[0147] 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.

[0148] Furthermore, according to the rotor member 400 of this embodiment, the rotor core portion 410 and the shaft portion 420 included in the rotor member 400 are each formed from ceramic. This reduces iron loss generated in the rotor member 400 and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, because the rotor core portion 410 and the shaft portion 420 are formed from a single ceramic member, heat generated in the rotor core portion 410 is easily conducted to the shaft portion 420. This makes it easier for heat generated in the rotor core portion 410 to be released to the outside of the motor via the shaft portion 420, thereby suppressing a temperature rise in the rotor member 400.

[0149] Furthermore, according to the rotor 40 of this embodiment, the rotor core 410 is provided with a magnetic portion 440 through which a magnetic circuit formed by the magnets 430 passes. The rotor member 400 provided in the rotor core 410 has relatively small iron loss and mechanical loss, and therefore is less likely to increase in temperature. This also suppresses temperature increases in the magnetic portion 440 provided in the rotor core 410, making it possible to suppress performance degradation of the magnetic portion 440 due to temperature changes.

[0150] 27 is a diagram schematically illustrating a cross section of a shaft portion of a sixth embodiment. The rotor member of the rotor of the sixth embodiment has a different configuration of the shaft portion compared to the rotor member of the fourth embodiment (FIG. 15).

[0151] The rotor member 400 of this embodiment is used in a motor that outputs rotational torque when power is supplied. The motor of this embodiment includes a rotor 40 having the rotor member 400, a stator 20, and a motor case 30. The rotor 40 is provided on the central axis of the motor of this embodiment so as to be rotatable about the central axis.

[0152] In this embodiment, the surface roughness Ra of the shaft portion 420 of the rotor member 400 is 15 μm or less, which results in a relatively small friction force between the shaft portions 421 and 422 and the bearings 310 and 320, respectively, making it easier for the rotor 40 to rotate relative to the stator 20 and enabling it to rotate at higher speeds.

[0153] FIG. 27 is a schematic diagram of a cross section of the shaft portion 420. It is a schematic diagram of an SEM image of the cross section of the shaft portion 420 exposed by etching, captured by a scanning electron microscope (SEM). The shaft portion 420 of this embodiment has a plurality of crystal grains 420a and a grain boundary liquid phase 420b surrounded by the crystal grains 420a. In this embodiment, the grain boundary liquid phase accounts for less than 10% of the cross section of the shaft portion 420 in terms of area ratio. When the grain boundary liquid phase accounts for less than 10% of the cross section in terms of area ratio, as in the shaft portion 420 of this embodiment, the crystal grains are in contact with each other in a relatively large area, which facilitates heat transfer. Alternatively, the thickness of the grain boundary liquid phase, which conducts heat less easily than the crystal grains, does not exceed a certain thickness, which reduces the likelihood of impeding heat transfer. In this embodiment, the average grain size of the crystal grains in the shaft portion 420 is 5.0 μm or less.

[0154] 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 third embodiment. The manufacturing method for the rotor member 400 differs from the manufacturing method for the rotor member 100 in that a molded extruded body is machined to have 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, to produce a machined 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 is not limited to this manufacturing method.

[0155] 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 to be used in IPM motors were fabricated, and the five types of samples were evaluated for "iron loss," "rotational strength," and "rotational efficiency" in the same manner as in the evaluation test of the first embodiment.

[0156] 28 is a diagram illustrating the evaluation results for the rotor member of this embodiment. Each of Samples 54 to 58 used in this evaluation test was produced by a method similar to the manufacturing method for the rotor member 400 of this embodiment. For each of Samples 54 to 58, the material of the ceramic particles as the main raw material was selected so as to have the composition of the "material" shown in FIG. 28. Note that the Al ２ O ３ and ZrO ２ The volume ratio of the two is 7:3 in both cases.

[0157] The "area ratio of grain boundary liquid phase" shown in Fig. 28 is a value indicating the area ratio occupied by the grain boundary liquid phase in the cross section of the shaft portion for each of Samples 54 to 58. The "average grain size" shown in Fig. 28 is a value indicating the average grain size of the ceramic crystal grains forming the sample for each of Samples 54 to 58. The "surface roughness" shown in Fig. 28 is a value indicating the surface roughness Ra of the shaft portion for each of Samples 54 to 58. The "area ratio of grain boundary liquid phase," "average grain size," and "surface roughness" shown in Fig. 28 were measured using the same methods as those used in the evaluation tests of the third embodiment.

[0158] 28 indicates the material forming the magnetic portion provided in the rotor core for each of Samples 54 to 58. Sample 54 has a magnetic portion formed from ferrite, while Sample 55 has a magnetic portion formed from a nanocrystalline soft magnetic material. Samples 56 to 58 each have a magnetic portion formed from an electromagnetic steel sheet.

[0159] In this evaluation test, the "iron loss" and "rotation efficiency" shown in FIG. 28 each show the results of a comparison with the comparative IPM motor shown in FIG. 21. The "iron loss" shown in FIG. 28 was evaluated using the same threshold values ​​as in the third embodiment, with the comparative IPM motor as the evaluation standard. As a result, as shown in FIG. 28, it was confirmed that, in terms of "iron loss," each of Samples 54 to 58, whose "material" was ceramic, exhibited superior performance (evaluation "A") compared to the comparative IPM motor.

[0160] As in the third embodiment, the "rotational strength" shown in Fig. 28 was determined by gradually increasing the rotational speed of the motors equipped with each of Samples 54 to 58, measuring the rotational speed at which the rotor member broke, and using the same threshold value as in the third embodiment. As a result, as shown in Fig. 28, it was confirmed that, in terms of "rotational strength," each of Samples 54 to 58, whose "material" was ceramic, exhibited superior performance (evaluated as "S") compared to the IPM motor of the comparative example.

[0161] As in the third embodiment, the "rotational efficiency" shown in Fig. 28 was evaluated using the comparative example IPM motor as the evaluation standard and the same threshold values ​​as in the third embodiment. As a result, as shown in Fig. 28, it was confirmed that in "rotational efficiency," each of Samples 54 to 58, whose "material" was ceramic, exhibited superior performance (evaluated as "A") compared to the comparative example IPM motor.

[0162] 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.

[0163] Furthermore, according to the rotor member 400 of this embodiment, the rotor core portion 410 and the shaft portion 420 included in the rotor member 400 are each formed of ceramic. This reduces iron loss generated in the rotor member 400 and suppresses an increase in mechanical loss due to friction, thereby suppressing heat generation due to iron loss and mechanical loss. Furthermore, the proportion of the grain boundary liquid phase in the cross section of the shaft portion 420 is smaller than the proportion of the crystal grains. This allows heat to be easily conducted in the shaft portion 420, making it easier for heat generated in the rotor core portion 410 to be released to the outside of the motor 1B via the shaft portion 420. This makes it possible to suppress a temperature rise in the rotor member 400.

[0164] Furthermore, according to the rotor 40 of this embodiment, the rotor core portion 410 is provided with a magnetic portion 440 through which the magnetic circuit Mgc formed by the magnets 430 passes. The rotor member 400 including the rotor core portion 410 is less likely to increase in temperature because iron loss and mechanical loss are relatively small. This also suppresses temperature increases in the magnetic portion 440 provided in the rotor core portion 410, thereby suppressing performance degradation of the magnetic portion 440.

[0165] Seventh Embodiment Fig. 29 is a cross-sectional view of a rotor according to a seventh embodiment. The rotor according to the seventh embodiment differs from the rotor according to the first embodiment (Fig. 1) in that the magnets are arranged in a Halbach array.

[0166] Similar to the rotor 40 of the fourth embodiment, the rotor 50 of the seventh embodiment is provided in a motor including a stator 20 and a motor case 30. The rotor 50 includes a rotor core portion 510, a plurality of magnets 520, a shaft portion 120, and a magnetic portion 540.

[0167] The rotor core portion 510 has a generally cylindrical shape, similar to the rotor core portion 410 of the fourth embodiment. One of the two end faces of the generally cylindrical rotor core portion 510 has an insertion hole 513 for inserting multiple magnets 520 and an insertion hole 514 for inserting a magnetic portion 540. As shown in FIG. 29 , both of the insertion holes 513 and 514 are formed so that a cross section perpendicular to the central axis C50 of the rotor 50 has an annular shape. As shown in FIG. 29 , the insertion hole 514 into which the magnetic portion 540 is inserted is formed inside the insertion hole 513 into which the multiple magnets 520 are inserted.

[0168] The multiple magnets 520 are arranged in a Halbach array in the rotor core portion 510. Specifically, the multiple magnets 520 inserted into the insertion holes 513 of the rotor core portion 510 are arranged around the entire circumference of the rotor core portion 510, and the magnetic pole direction of each of the multiple magnets 520 is determined so that the magnetic field strength is maximized on the outside of the rotor core portion 510. In Figure 29, the magnetic pole direction of each of the multiple magnets 520 is indicated by a solid arrow Mp.

[0169] The magnetic portion 540 is provided in the rotor core portion 510 and is made of a soft magnetic material. In this embodiment, the magnetic portion 540 is made of a nanocrystalline soft magnetic material. The magnetic portion 540 is supported by the rotor core portion 510 by being inserted into an insertion hole 514 formed in the rotor core portion 510.

[0170] Next, an evaluation test of the rotor of this embodiment will be described. In this evaluation test, three types of motor samples with magnets in a Halbach array were fabricated, and the "iron loss" and "rotation efficiency" of each of the three types of samples were evaluated in the same manner as in the evaluation test of the rotor of the first embodiment.

[0171] FIG. 30 is a diagram illustrating the evaluation results for the rotor of this embodiment. The three types of samples (samples 59 to 61) used in this evaluation test were motors equipped with rotors manufactured using a method similar to the manufacturing method for rotor 10 of the fourth embodiment, with magnets arranged in a Halbach array. Each of samples 59 to 61 was provided with a magnetic portion formed of a nanocrystalline soft magnetic material. The "iron loss" and "rotation efficiency" shown in FIG. 30 show the results of a comparison of each of the three samples with a motor (not shown) equipped with a rotor in which the rotor's "material" was electromagnetic steel sheet and multiple magnets were arranged in a Halbach array in the rotor core (hereinafter simply referred to as the "comparative Halbach array motor"), evaluated using the same method as the evaluation test of the first embodiment.

[0172] As shown in Figure 30, it was confirmed that Samples 59 to 61, in which the "rotor" material was ceramic, exhibited superior performance in both "iron loss" and "rotational efficiency" to the comparative Halbach array motor. In this way, it was confirmed that a motor in which magnets are arranged in a Halbach array exhibits superior performance by forming the rotor core and shaft of the rotor from ceramic.

[0173] According to the rotor 50 of this embodiment described above, the rotor core 510 and the shaft 120 are made of ceramic, which makes it possible to reduce iron loss generated in the rotor core 510 and the like compared to electromagnetic steel sheet, iron, etc. Furthermore, since the ceramic that forms the shaft 120 has a smaller thermal expansion coefficient than metal, it is possible to suppress an increase in mechanical loss in the rotor 50. This improves the efficiency of the motor of this embodiment.

[0174] Furthermore, according to the rotor 50 of this embodiment, the magnets 520 are arranged in a Halbach array in the rotor core portion 510. The rotor core portion 510 is made of ceramic and has relatively low iron loss, so the strength of the magnetic field formed by the magnets 520 can be further strengthened outside the rotor core portion 510. This can further improve the efficiency of the motor of this embodiment.

[0175] Eighth Embodiment Figure 31 is a cross-sectional view of an axial gap motor according to an eighth embodiment. Figure 32 is a cross-sectional view taken along line B-B in Figure 31. The rotor of the eighth embodiment differs from the rotor of the first embodiment (Figure 1) in the shape of the rotor core and the position of the magnets in the rotor core.

[0176] The rotor 60 of this embodiment is used in a motor 1H that outputs rotational torque when supplied with electric power. The motor 1H includes the rotor 60, a motor stator 70, and a motor case 30. The rotor 60 is provided on a central axis C1H of the motor 1H and is rotatable about the central axis C1H.

[0177] The rotor 60 includes a rotor core portion 610 made of ceramic, a magnet 620 arranged in the rotor core portion 610, a shaft portion 630 made of ceramic and connected to the rotor core portion 610, and a magnetic portion 640. In the rotor 60 of this embodiment, the rotor core portion 610 and the shaft portion 630 are formed from a single ceramic member. However, the rotor core portion 610 and the shaft portion 630 may be formed from separate members and joined together.

[0178] The rotor core portion 610 has a generally circular disk shape. A plurality of through holes 613 having openings on each of two main surfaces 611, 612 are formed in the generally circular disk-shaped rotor core portion 610. A magnet 620 is disposed in each of the plurality of through holes 613. An insertion hole 614 for inserting a magnetic portion 640 is formed in one main surface 611 of the two main surfaces 611, 612 of the rotor core portion 610.

[0179] The magnet 620 is mounted on the rotor core portion 610 by being inserted into the through-hole 613 of the rotor core portion 610. In this embodiment, as shown in FIG. 31 , the magnet 620 is arranged in the rotor core portion 610 so that its longitudinal direction is perpendicular to the axial direction of the shaft portion 630 (the direction of the central axis C1H of the motor 1H). Here, "perpendicular" includes not only a case where the magnet 620 intersects at a right angle in the strict sense, but also a case where the magnet 620 intersects at an apparent right angle. The magnet 620 has exposed surfaces 621 and 622 that are exposed from the two main surfaces 611 and 612 of the rotor core portion 610, respectively.

[0180] The shaft portion 630 has two shaft portions 631, 632 connected to the center of the rotor core portion 610 so that their axial directions are perpendicular to the main surfaces 611, 612 of the rotor core portion 610. The two shaft portions 631, 632 are formed so as to protrude from the two main surfaces 611, 612 of the rotor core portion 610, respectively (see FIG. 31 ). The shaft portion 631 is rotatably supported by a bearing 310 of the motor case 30. The shaft portion 632 is rotatably supported by a bearing 320 of the motor case 30.

[0181] The magnetic portion 640 is provided in the rotor core portion 610 and is made of a soft magnetic material. In this embodiment, the magnetic portion 640 is made of a nanocrystalline soft magnetic material. The magnetic portion 640 is mounted on the rotor core portion 610 by being inserted into an insertion hole 614 formed in the rotor core portion 610.

[0182] The stator 70 has a stator core 710 and a winding 720 for generating a magnetic field. The motor 1H of this embodiment includes two stators 70, which are arranged to face the exposed surfaces 621 and 622 of the magnet 620, respectively.

[0183] The stator core portion 710 has a plurality of columnar portions 711 formed so that the axial direction of each columnar portion 711 is aligned with the central axis C1H of the motor 1H. The stator core portion 710 is formed by laminating a plurality of electromagnetic steel plates.

[0184] The winding 720 is a conductor wire coated with an insulator. The winding 720 is wound around each of the plurality of columnar portions 711 of the stator core portion 710. That is, in this embodiment, the winding axis of the winding 720 is approximately parallel to the central axis C1H of the motor 1H. When electricity supplied from outside the motor 1H flows through the winding 720, the winding generates a magnetic field.

[0185] In the motor 1H of this embodiment, the first stator 70, the rotor 60, and the second stator 70 are arranged in this order along the direction of the central axis C1H. As a result, in the motor 1H, a magnetic flux for rotating the rotor 60 is generated mainly along the direction of the central axis C1H. In other words, the motor 1H is a so-called axial gap motor in which the gap between the rotor 60 and the two stators 70 is defined along the direction of the central axis C1H.

[0186] Next, an evaluation test of the rotor of this embodiment will be described. In this evaluation test, four types of axial gap motor samples were fabricated, and the "iron loss" and "rotation efficiency" of each of the four samples were evaluated in the same manner as in the evaluation test of the rotor of the first embodiment.

[0187] FIG. 33 illustrates the evaluation results for the rotor of this embodiment. Samples 62 to 65 used in this evaluation test were axial gap motors equipped with rotors manufactured using a method similar to the manufacturing method for rotor 10 of the first embodiment. Each of Samples 62 to 65 had a magnetic portion formed from a nanocrystalline soft magnetic material. The "iron loss" and "rotation efficiency" shown in FIG. 33 show the results of a comparison of each of the four samples with an axial gap motor (not shown) (hereinafter simply referred to as the "comparative axial gap motor") that has the same structure as the axial gap motor of this embodiment shown in FIGS. 31 and 32, but has a rotor formed from laminated electromagnetic steel sheets, with a rotor core and a shaft. The comparison results were evaluated using the same method as the evaluation test of the first embodiment.

[0188] As shown in Figure 33, it was confirmed that Samples 62 to 65, in which the "material" of the "rotor" is ceramic, exhibited superior performance in both "iron loss" and "rotational efficiency" compared to the axial gap motor of the comparative example. In this way, it was confirmed that an axial gap motor in which the rotor core and shaft of the rotor are made of ceramic exhibits superior performance.

[0189] According to the rotor 60 of this embodiment described above, the rotor core 610 and the shaft 630 are made of ceramic, which makes it possible to reduce iron loss generated by the rotor core 610 and the like compared to electromagnetic steel sheet, iron, etc. Furthermore, since the ceramic that forms the shaft 630 has a smaller thermal expansion coefficient than metal, it is possible to suppress an increase in mechanical loss in the rotor 60. This makes it possible to improve the efficiency of the motor 1H.

[0190] Furthermore, according to the rotor 60 of this embodiment, the shaft portion 630 is connected to the center of the rotor core portion 610 so that its axial direction is perpendicular to the main surfaces 611, 612 of the rotor core portion 610. The magnet 620 is arranged in the rotor core portion 610 so that its longitudinal direction is perpendicular to the axial direction of the shaft portion 630. This allows the motor 1H including the rotor 60 to be an axial gap motor in which the main direction of the magnetic flux in the magnetic circuit formed by the magnet 620 is along the axial direction of the shaft portion 630. The rotor core portion 610 of the motor 1H is made of ceramic with relatively low iron loss, which further improves the efficiency of the motor 1H, which is an axial gap motor.

[0191] 34 is a cross-sectional view of an axial gap motor according to a ninth embodiment. The rotor of the ninth embodiment is different from the rotor of the first embodiment (FIG. 1) in the shape of the rotor core and the position of the magnets in the rotor core.

[0192] The rotor 80 of this embodiment is used in a motor 1I that outputs rotational torque when supplied with electric power. The motor 1I includes the rotor 80, a motor stator 85, and a motor case 30. The rotor 80 is provided on a central axis C1I of the motor 1I so as to be rotatable about the central axis C1I.

[0193] The rotor 80 includes a rotor core portion 810 made of ceramic, magnets 820 arranged in the rotor core portion 810, a shaft portion 830 made of ceramic and connected to the rotor core portion 810, and a magnetic portion 840. In the rotor 80 of this embodiment, the rotor core portion 810 and the shaft portion 830 are formed from a single ceramic member. However, the rotor core portion 810 and the shaft portion 830 may be formed from separate members and joined together.

[0194] The rotor core portion 810 has two plate-shaped members 811 and 812, each having a substantially circular shape. The plate-shaped member 811 has a pair of main surfaces 811a and 811b. The plate-shaped member 812 has a pair of main surfaces 812a and 812b. As shown in FIG. 34 , the two plate-shaped members 811 and 812 are arranged so that one main surface 811a of the plate-shaped member 811 faces one main surface 812a of the plate-shaped member 812. Insertion holes 811d and 812d for inserting the magnetic portion 840 are formed in side surfaces 811c and 812c of the two plate-shaped members 811 and 812, respectively.

[0195] In the plate-shaped member 811, the magnet 820 is disposed on one of the pair of main surfaces 811a, 811b, namely, the main surface 811a. In the plate-shaped member 812, the magnet 820 is disposed on one of the pair of main surfaces 812a, 812b, namely, the main surface 812a. As a result, in the motor 1H of this embodiment, the magnets 820 provided on each of the two plate-shaped members 811, 812 are disposed so as to face each other.

[0196] The shaft portion 830 connects the two plate-shaped members 811, 812 of the rotor core portion 810 so that the magnets 820 arranged on each of the two plate-shaped members 811, 812 face each other. Specifically, the shaft portion 830 has a connecting portion 831 and two protrusions 832, 833. The connecting portion 831 connects the two plate-shaped members 811, 812 of the rotor core portion 810. The protrusion 832 is formed to protrude from the main surface 811b of the plate-shaped member 811. The protrusion 832 is rotatably supported by the bearing 310 of the motor case 30. The protrusion 833 is formed to protrude from the main surface 812b of the plate-shaped member 812. The protrusion 833 is rotatably supported by the bearing 320 of the motor case 30.

[0197] The magnetic portion 840 is provided in the rotor core portion 810 and is made of a soft magnetic material. In this embodiment, the magnetic portion 840 is made of a nanocrystalline soft magnetic material. The magnetic portion 840 is mounted on the rotor core portion 810 by being inserted into the insertion holes 811d, 812d formed in the rotor core portion 810.

[0198] The stator 85 has a stator core 860 and windings 870 for generating a magnetic field. In the motor 1I of this embodiment, the stator 85 is fixed to the motor case 30 so as to be disposed between the magnets 820 supported by the two plate-like members 811 and 812 of the rotor core 810.

[0199] The stator core portion 860 has a columnar portion 861 formed so that its axial direction is aligned with the central axis C1I of the motor 1I. The stator core portion 860 is formed by laminating a plurality of electromagnetic steel plates.

[0200] The winding 870 is a conductor wire coated with an insulator. The winding 870 is wound around each of the plurality of columnar portions 861 of the stator core portion 860. That is, in this embodiment, the winding axis of the winding 870 is approximately parallel to the central axis C1I of the motor 1I. When electricity supplied from outside the motor 1I flows through the winding 870, the winding 870 generates a magnetic field.

[0201] In the motor 1I of this embodiment, the plate-shaped member 811 of the rotor core 810, the stator 85, and the plate-shaped member 812 of the rotor core 810 are arranged in this order along the direction of the central axis C1I. As a result, in the motor 1I, a magnetic flux for rotating the rotor 80 is generated mainly along the direction of the central axis C1I. In other words, the motor 1I is a so-called axial gap motor in which the gap between the two rotors 80 and the stator 85 is defined along the direction of the central axis C1I.

[0202] According to the rotor 80 of this embodiment described above, the rotor core portion 810 and the shaft portion 830 are formed from ceramic, which makes it possible to reduce iron loss generated by the rotor core portion 810 and the like compared to electromagnetic steel sheet, iron, etc. Furthermore, since the ceramic forming the shaft portion 830 has a smaller thermal expansion coefficient than metal, it is possible to suppress an increase in mechanical loss in the rotor 80. This makes it possible to improve the efficiency of the motor 1I.

[0203] Furthermore, according to rotor 80 of this embodiment, in rotor 80, magnet 820 is arranged on one main surface 811a of a pair of main surfaces 811a, 811b of plate-shaped member 811 of rotor core portion 810, and magnet 820 is arranged on one main surface 812a of a pair of main surfaces 812a, 812b of plate-shaped member 812 of rotor core portion 810. Magnet 820 of plate-shaped member 811 and magnet 820 of plate-shaped member 812 are arranged to face each other, and winding 870, whose winding axis is approximately parallel to central axis C1I of motor 1I, is arranged between magnet 820 of plate-shaped member 811 and magnet 820 of plate-shaped member 812. As a result, motor 1I including rotor 80 can be an axial gap motor in which the main direction of magnetic flux in the magnetic circuit formed by magnet 820 is along the axial direction of shaft portion 830. The rotor core 810 of the motor 1I is made of ceramic, which has a relatively small iron loss, and therefore the efficiency of the motor 1I, which is an axial gap motor, can be further improved.

[0204] <Tenth embodiment> Fig. 35 is a cross-sectional view of a rotor including a rotor according to a tenth embodiment. The rotor according to the tenth embodiment differs from the rotor according to the fourth embodiment (Fig. 15) in that it does not include a magnetic portion.

[0205] Like the rotor 40 of the fourth embodiment, the rotor 40 of the tenth embodiment is provided in a motor including a stator 20 and a motor case 30. The rotor 40 includes a rotor core portion 410 made of ceramic, a magnet 430 disposed inside the rotor core portion 410, and a shaft portion 120 connected to the rotor core portion 410 and made of ceramic.

[0206] According to the rotor 40 of this embodiment described above, the rotor core 410 and the shaft 120 are made of ceramic, which makes it possible to reduce iron loss generated by the rotor core 410 and the like compared to electromagnetic steel sheets, iron, etc. Furthermore, since the ceramic that forms the shaft 120 has a smaller thermal expansion coefficient than metal, it is possible to suppress an increase in mechanical loss in the rotor 40.

[0207] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0208] [Variation 1] In the first and second embodiments, the rotor member is formed of silicon nitride. 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 an oxide, a carbide, and a nitride, but is not limited to these. The rotor member may be formed of a mixture of alumina and zirconia. When the ceramic forming the rotor member is at least one of an oxide, a carbide, and a 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.

[0209] [Variation 2] In the first embodiment, the ceramic forming the rotor member has an average crystal grain size of 5.0 μm or less and a porosity of 3% or less. The characteristics 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 5.0 μm or less and the porosity is 3% or less, the strength of the rotor member becomes relatively high.

[0210] [Variation 3] In the first embodiment, the thermal conductivity in the axial direction of the shaft portion 120 is set to be at least 2 W / (m·K) greater 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 greater 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.

[0211] [Modification 4] In the above-described embodiment, the rotor core portion and the shaft portion of the rotor member are formed from a single ceramic member. However, the relationship between the rotor core portion and the shaft portion is not limited to this.

[0212] Figure 36 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 Figure 36, 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 the 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, because the rotor core portion 110 and the shaft portion 120 are made of ceramic, it is possible to reduce iron loss and suppress an increase in mechanical loss.

[0213] Figure 37 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 Figure 37, 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, because the rotor core portion 110 and the shaft portion 120 are made of ceramic, it is possible to reduce iron loss and suppress an increase in mechanical loss.

[0214] [Modification 5] In the second embodiment, the rotor member has a thermal expansion coefficient of 6.0×10 －６ / K or less, and the specific gravity is 5.0 g / cm ３ However, the properties of the rotor member are not limited to these. －６ / K or the specific gravity may be 5.0 g / cm ３ The thermal expansion coefficient may be 6.0×10 or more. －６ / K or less, and the specific gravity is 5.0 g / cm ３ By satisfying the above, it is possible to reduce the electric power required to rotate the rotor member at a predetermined rotation speed.

[0215] [Variation 6] In the second embodiment, the connection portion between the rotor core portion and the shaft portion is formed to have an R-shape with an R of 0.2 mm or more. The shape of the connection portion between the rotor core portion and the shaft portion is not limited to this. The R-shape may be approximately 0.1 mm. By forming the connection portion P10 in an R-shape, stress generated in the rotor member is less likely to concentrate on the connection portion, and damage due to stress can be suppressed.

[0216] [Variation 7] In the third embodiment, the ceramic forming the rotor member has an average crystal grain size of 5.0 μm or less. The average crystal grain size of the ceramic forming the rotor member may be greater than 5.0 μm. When the average crystal grain size is 5.0 μm or less, the strength of the rotor member becomes relatively high, and when the average crystal grain size is 2.0 μm or less, the strength of the rotor member becomes even higher.

[0217] [Variation 8] In the third embodiment, the shaft portion has a surface roughness Ra of 15 μm or less. The surface roughness Ra of the shaft portion may be greater than 15 μm, but is preferably 15 μm or less, and more preferably 10 μm or less. When the surface roughness Ra of the shaft portion is reduced, the frictional force between the portion that rotatably supports the shaft portion and the shaft portion is reduced, making it easier for the rotor member to rotate.

[0218] [Modification 9] In the rotor of the seventh embodiment in which the magnets are arranged in a Halbach array, and in the axial gap motors of the eighth and ninth embodiments, the rotor includes a magnetic portion formed from a nanocrystalline soft magnetic material. The magnetic portion is not necessary, but the presence of the magnetic portion allows the magnetic circuit formed by the magnets to pass preferentially through the magnetic portion. This further reduces iron loss generated in the rotor core, further suppressing temperature rise in the rotor core and further suppressing performance degradation of the magnetic portion.

[0219] 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.

[0220] <Application Example 1> A rotor member for a motor, comprising: a rotor core portion formed of ceramic and having a support portion for supporting a magnet; and a shaft portion formed of ceramic and connected to the rotor core portion. <Application Example 2> The rotor member according to Application Example 1, wherein the ceramic is at least one of oxide, carbide, and nitride, the average grain size of crystal grains is 5.0 μm or less, and the porosity is 3% or less. <Application Example 3> The rotor member according to Application Example 1 or Application Example 2, wherein the thermal conductivity in the axial direction of the shaft portion is greater than the thermal conductivity in a direction perpendicular to the axial direction by 2 W / (m·K) or more. <Application Example 4> The rotor member according to any one of Application Examples 1 to 3, wherein the rotor core portion and the shaft portion are formed from a single ceramic member. <Application Example 5> The rotor member according to any one of Application Examples 1 to 4, wherein the thermal expansion coefficient is 6.0×10 －６ / K or less, and the specific gravity is 5.0 g / cm ３A rotor member characterized by the following. <Application Example 6> The rotor member according to any one of Application Examples 1 to 5, wherein the rotor core portion has a generally columnar shape, the shaft portion is formed so as to protrude from an end face of the rotor core portion, and a connection portion between the rotor core portion and the shaft portion is formed so as to have an R-shape (curved shape) with an R (radius of curvature) of 0.2 mm or more. <Application Example 7> The rotor member according to any one of Application Examples 1 to 6, wherein the shaft portion has a plurality of crystal grains and a grain boundary liquid phase surrounded by the crystal grains, and a proportion of the grain boundary liquid phase in a cross section of the shaft portion is less than 10% in terms of area ratio. <Application Example 8> The rotor member according to any one of Application Examples 1 to 7, wherein the average grain size of the crystal grains in the shaft portion is 5.0 μm or less. <Application Example 9> The rotor member according to any one of Application Examples 1 to 8, wherein the shaft portion has a surface roughness Ra of 15 μm or less. <Application Example 10> A rotor for a motor, comprising: the rotor member according to any one of Application Examples 1 to 9; a magnet supported by the support portion; and a magnetic portion provided in the rotor core portion and formed of metal or ceramic having soft magnetic properties, wherein the magnet forms a magnetic circuit passing through the magnetic portion. <Application Example 11> A rotor for a motor, comprising: the rotor member according to any one of Application Examples 1 to 9; and a magnet disposed on an interior or outer surface of the rotor core portion. <Application Example 12> The rotor according to Application Example 11 further comprises: a magnetic portion provided in the rotor core portion and formed of a soft magnetic material, wherein the magnet forms a magnetic circuit passing through the magnetic portion. <Application Example 13> The rotor according to any one of Application Examples 10 to 12, wherein the magnets are arranged in the rotor core in a Halbach array.<Application Example 14> The rotor according to any one of Application Examples 10 to 13, wherein the rotor core portion has a substantially circular plate shape, The shaft portion is connected to a center of the rotor core portion such that its axial direction is perpendicular to a main surface of the rotor core portion, and The magnet is arranged in the rotor core portion such that its longitudinal direction is perpendicular to the axial direction of the shaft portion. <Application Example 15> The rotor according to any one of Application Examples 10 to 13, wherein the rotor core portion has two plate-like members having a substantially circular shape, The magnet is arranged on one of a pair of main surfaces of each of the two plate-like members, and The shaft portion is connected to the two plate-like members such that the magnets arranged on each of the two plate-like members face each other. <Application Example 16> An axial gap motor comprising: the rotor according to any one of Application Examples 10 to 13; and a motor stator having windings for generating a magnetic field, wherein the magnetic field is formed such that the direction of magnetic flux is along the axial direction of the shaft portion. <Application Example 17> A motor comprising: the rotor according to any one of Application Examples 10 to 15; and a motor stator arranged outside the rotor core portion, the stator having windings for generating a magnetic field. <Application Example 18> A motor comprising: the rotor member according to any one of Application Examples 1 to 9; a magnet supported by the support portion; and a motor stator arranged outside the rotor core portion, the stator having windings for generating a magnetic field.

[0221] DESCRIPTION OF THE PREFERRED EMBODIMENTS 1A, 1B, 1D, 1E, 1H, 1I... Motor 10, 40, 50, 60, 80... Rotor 20, 70, 85... Stator 100, 400... Rotor member 110, 410, 510, 610, 810... Rotor core portion 111, 411... Support portion 120, 121, 122, 420, 421, 422, 630, 631, 632... Shaft portion 130, 430, 520, 620, 820... Magnet 440, 540, 640, 840... Magnetic portion 220, 720, 870... Winding Mgc... Magnetic circuit

Claims

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

2. A rotor member according to claim 1, wherein the ceramic is at least one of oxide, carbide, and nitride, the average grain size of the crystal grains is 5.0 μm or less, and the porosity is 3% or less.

3. A rotor member according to claim 1 or 2, characterized in that 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.

4. A rotor member according to any one of claims 1 to 3, characterized in that the rotor core portion and the shaft portion are formed from a single ceramic member.

5. A rotor member according to any one of claims 1 to 4, wherein the thermal expansion coefficient is 6.0 x 10 －６ / K or less, and the specific gravity is 5.0 g / cm ３ A rotor member characterized in that:

6. A rotor member according to any one of claims 1 to 5, characterized in that the rotor core portion has a generally columnar shape, the shaft portion is formed so as to protrude from an end face of the rotor core portion, and the connecting portion between the rotor core portion and the shaft portion is formed so as to have an R-shape (curved shape) with an R (radius of curvature) of 0.2 mm or more.

7. A rotor member according to any one of claims 1 to 6, characterized in that the shaft portion has a plurality of crystal grains and a grain boundary liquid phase surrounded by the crystal grains, and the proportion of the grain boundary liquid phase in the cross section of the shaft portion is less than 10% in terms of area ratio.

8. A rotor member according to any one of claims 1 to 7, characterized in that the average grain size of the crystal grains in the shaft portion is 5.0 μm or less.

9. A rotor member according to any one of claims 1 to 8, characterized in that the shaft portion has a surface roughness Ra of 15 μm or less.

10. A rotor for a motor, comprising: a rotor member according to any one of claims 1 to 9; a magnet supported by the support portion; and a magnetic portion provided in the rotor core portion and formed of a metal or soft magnetic ceramic, wherein the magnet forms a magnetic circuit passing through the magnetic portion.

11. A rotor for a motor, comprising: a rotor member according to any one of claims 1 to 9; and a magnet disposed inside or on the outer surface of the rotor core portion.

12. The rotor according to claim 11 further comprises a magnetic section formed of a soft magnetic material and provided in the rotor core, and the magnet forms a magnetic circuit passing through the magnetic section.

13. A rotor according to any one of claims 10 to 12, characterized in that the magnets are arranged in the rotor core portion in a Halbach array.

14. A rotor as claimed in any one of claims 10 to 13, characterized in that the rotor core portion has a substantially circular disk shape, the shaft portion is connected to the center of the rotor core portion so that its axial direction is perpendicular to the main surface of the rotor core portion, and the magnet is arranged in the rotor core portion so that its longitudinal direction is perpendicular to the axial direction of the shaft portion.

15. A rotor as claimed in any one of claims 10 to 14, characterized in that the rotor core portion has two plate-like members having an approximately circular shape, the magnets are arranged on one of a pair of main surfaces of each of the two plate-like members, and the shaft portion is connected to the two plate-like members so that the magnets arranged on each of the two plate-like members face each other.

16. An axial gap motor comprising: a rotor according to any one of claims 10 to 15; and a stator for a motor having windings for forming a magnetic field, wherein the magnetic field is formed such that the direction of magnetic flux is along the axial direction of the shaft portion.

17. A motor comprising: a rotor according to any one of claims 10 to 15; and a stator for the motor, disposed outside the rotor core and having windings for generating a magnetic field.

18. A motor comprising: a rotor member according to any one of claims 1 to 9; a magnet supported by the support portion; and a stator for the motor, arranged outside the rotor core portion and having windings for generating a magnetic field.

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