Magnet scattering prevention protective tube, rotor for permanent magnet synchronous electric motor, and permanent magnet synchronous electric motor

Abstract

To provide a magnet scattering prevention protective tube that suppresses heat generation caused by friction with air during rotation when used in a motor rotating in air.SOLUTION: The cylindrical magnet scattering prevention protective tube for a permanent magnet synchronous electric motor that covers the outer peripheral surface of a permanent magnet is made of carbon fiber reinforced resin, and has a dynamic friction coefficient of 0.3 or less in the rotational direction of the outer surface against a mirror-finished steel plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a magnet scattering prevention protection tube, a rotor for a permanent magnet synchronous electric motor, and a permanent magnet synchronous electric motor. [Background technology]

[0002] In recent years, the adoption of permanent magnet synchronous electric motors has become widespread as various electrical devices become smaller, lighter, and more powerful. High-speed rotor rotation is effective in achieving high power output, which requires motors and their components to be designed with materials that can withstand the centrifugal force that occurs during high-speed rotation. In high-power permanent magnet synchronous electric motors, magnets are attached to the surface of the rotor shaft, and a protective tube is placed around the magnet to prevent the magnet from scattering due to centrifugal force. Carbon fiber reinforced plastics (CFRP), for example, are used for this protective tube, both from the perspective of reducing the motor's weight and as mentioned above, as a high-strength material that can withstand centrifugal force.

[0003] For example, Patent Document 1 discloses a sliding member for wet lubrication that is made of a molded product of a resin composition containing (A) a polyether aromatic ketone resin, (B) carbon fibers having an average fiber length of 1 mm or more, and (C) reinforcing fibers having an average fiber length of 300 μm or less, wherein the sliding member has a surface roughness (Sz) of 60 μm or less and a flexural modulus of elasticity of 12 GPa or more.

[0004] Furthermore, Patent Document 2 discloses a rolling bearing for use in high-speed rotating members such as machine tool spindles, in which the surface roughness of the inner surface of the cage pocket and the guided surface is set to an arithmetic mean roughness Ra of 1.0 to 9.8 μm and a maximum height Rt of 10.1 to 102.9 μm.

[0005] Patent Document 3 also discloses a rolling bearing for supporting a main shaft to which blades are attached in a wind power generator, the rolling bearing comprising inner and outer rings that are raceways, rolling elements interposed between the inner and outer rings, and a retainer that rotatably holds the rolling elements, the rolling bearing having a multi-layer coating formed thereon consisting of a first layer that directly covers the surface of the retainer, and an nth layer (n is an integer of 2 or greater) that covers the (n-1)th layer, the first layer being made of a synthetic resin blended with a filler, and the second and subsequent layers being made of an unfilled synthetic resin or a synthetic resin blended with a solid lubricant.

[0006] Patent Document 4 also discloses a rolling bearing for supporting a main shaft of a wind power generator, the rolling bearing comprising inner and outer rings that serve as raceways, rolling elements interposed between the inner and outer rings, and a cage that rotatably holds the rolling elements, the rolling bearing being for supporting a main shaft to which blades are attached, wherein the surface of the cage is formed with a coating made of a resin composition that contains a synthetic resin, fullerene, and at least one disulfide selected from molybdenum disulfide and tungsten disulfide, and the resin composition contains 0.1 to 10% by volume of the fullerene and 0.5 to 20% by volume of the disulfide.

[0007] Patent Document 5 also discloses a rolling bearing for an alternator, such as a deep groove ball bearing that supports a rotor that rotates facing the stator of an automotive alternator and the rotating shaft of the rotor, in which the retainer that holds the rolling elements of the rolling bearing is formed from a resin composition containing polyamide 9T resin with a polymerization degree of 60 to 120 and a fibrous filler, and the sliding surface of the retainer with which the rolling elements slide is formed with scattered dimples to provide oil retention.

[0008] Patent Document 6 also discloses a rolling bearing in which the raceway surfaces of the inner and outer rings are provided with an oil-repellent layer that has been subjected to an oil-repellent treatment such that the contact angle θ with respect to the lubricating oil J is 50° or greater, via a shot-peened layer that has been subjected to a shot-peened treatment to achieve a surface roughness (Ra) of 0.05 μm or greater and 2.0 μm or less.

[0009] Patent Document 7 also discloses a core material for helical processing that contains, by mass%, C: 0.01% or less, Si: 4% or less, Mn: 2% or less, Al: 2% or less, P: 0.1% or less, S: 0.02% or less, N: 0.005% or less, with the remainder being Fe and unavoidable impurities, and whose crystal grain size d (μm) and the inner / outer diameter ratio of the core back portion of the stator core (inner diameter Di / outer diameter Do) satisfy the relationship "d≦20+100×(Di / Do)2 ... (1)" (where Di is the inner diameter (core back portion) of the stator core, and Do is the outer diameter of the stator core). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2022-76249 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-095469 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-156295 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-133403 [Patent Document 5] Japanese Patent Application Laid-Open No. 2008-144777 [Patent Document 6] Japanese Patent Application Laid-Open No. 2007-100759 [Patent Document 7] Japanese Patent Application Laid-Open No. 2005-187861 Summary of the Invention [Problem to be solved by the invention]

[0011] In permanent magnet synchronous electric motors, carbon fiber reinforced plastic (CFRP) is used, for example, for the protective tube that prevents magnets from scattering and is attached to the outer surface of the magnet. However, when the rotor rotates at high speed, surface friction with the air causes the surface temperature of the protective tube to rise, which can reduce the mechanical strength of the CFRP. Therefore, there is a need to suppress heat generation in the protective tube due to friction with the air.

[0012] In response to this, the present disclosure aims to provide a magnet scattering prevention protective tube that, when used in a motor that rotates in the air, suppresses heat generation due to friction with the air that accompanies rotation, a rotor for a permanent magnet synchronous electric motor that has the magnet scattering prevention protective tube, and a permanent magnet synchronous electric motor. [Means for solving the problem]

[0013] The means for solving the problem include the following aspects. <1> A cylindrical magnet scattering prevention protective tube that covers the outer peripheral surface of a permanent magnet in a permanent magnet synchronous electric motor, Made of carbon fiber reinforced resin, The coefficient of dynamic friction in the direction of rotation of the outer surface against a mirror-finished steel plate is 0.3 or less. Protective tube to prevent magnet scattering. <2> The dynamic friction coefficient is 0.1 or less. <1> The magnet scattering prevention protective tube described in <3> The cylindrical magnet scattering prevention protective tube is divided into two or more parts in the axial or rotational direction. <1> or <2> The magnet scattering prevention protective tube described in <4> A rotor shaft; a permanent magnet attached to the outer peripheral surface of the rotor shaft; Covering the entire outer peripheral surface of the permanent magnet, <1> ~ <3> a magnet scattering prevention protective tube according to any one of the preceding claims; A rotor of a permanent magnet synchronous electric motor having: <5> The permanent magnet synchronous electric motor rotates at 10,000 rpm or more. <4> A rotor for a permanent magnet synchronous electric motor according to claim 1. <6> <4> or <5> A permanent magnet synchronous electric motor having a rotor according to claim 1. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to provide a magnet scattering prevention protective tube that, when used in a motor that rotates in the air, suppresses heat generation due to friction with the air that accompanies rotation, a rotor for a permanent magnet synchronous electric motor that has the magnet scattering prevention protective tube, and a permanent magnet synchronous electric motor. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing a configuration of a rotor according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a schematic perspective view showing the collection position of a measurement sample used to measure the coefficient of dynamic friction in the rotational direction of the outer surface of the magnet scattering prevention protective tube. [Figure 3] FIG. 2 is a schematic perspective view showing an embodiment of a magnet scattering prevention protective tube used in tests in the examples. [Figure 4] 1 is a schematic perspective view showing a magnet scattering prevention protective tube according to an embodiment of the present disclosure, which is a protective tube divided in the axial direction. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment that is an example of the present disclosure will be described. In this specification, when a numerical range expressed using "to" is not preceded or followed by "greater than" or "less than," it means a range that includes these numerical values ​​as the lower and upper limits. When "to" is preceded or followed by "greater than" or "less than," it means a range that does not include these numerical values ​​as the lower or upper limit. In the present specification, the upper limit of a numerical range may be replaced by the upper limit of another numerical range, or may be replaced by a value shown in an example. The lower limit of a numerical range may be replaced by the lower limit of another numerical range, or may be replaced by a value shown in an example. Furthermore, "%" in the content means "% by mass" unless otherwise specified. The content (%) of "0 or more" means that the component is an optional component and does not need to be contained.

[0017] <Magnetic scattering prevention protection tube> A magnet scattering prevention protective tube (hereinafter also simply referred to as a "protective tube") according to an embodiment of the present disclosure covers the outer peripheral surface of a permanent magnet in a permanent magnet synchronous electric motor (hereinafter also simply referred to as a "motor"). The protective tube is cylindrical and made of carbon fiber reinforced plastic (CFRP). The protective tube has a coefficient of dynamic friction of 0.3 or less in the rotational direction of the outer surface against a mirror-finished steel plate.

[0018] The protective tube according to the embodiment of the present disclosure has the above-described configuration, and in a motor that rotates in the air, heat generation due to friction with the air caused by rotation is suppressed. The reason for this effect is presumed to be as follows.

[0019] In permanent magnet synchronous electric motors, magnets are attached to the surface of the rotor shaft, and a protective tube is placed around the magnet to prevent the magnets from flying off due to centrifugal force. This protective tube is typically made of carbon fiber reinforced plastic (CFRP). However, as the rotor rotates at high speed, surface friction with the air can cause the surface temperature of the CFRP protective tube to rise. When the surface temperature of the protective tube rises, the thermal expansion and softening of the resin in the CFRP reduces the mechanical strength of the CFRP. As a result, conventional CFRP protective tubes have sometimes burst due to insufficient strength. Furthermore, as the need for higher motor output continues to increase and even higher rotation speeds are being considered, there is a demand for CFRP protective tubes that can ensure sufficient strength to withstand the increase in surface temperature caused by high-speed rotation.

[0020] Incidentally, in the past, inventions relating to bearings with low sliding heat generation under high-speed sliding conditions have been disclosed (for example, Patent Documents 1 to 7, etc.). However, the protective tube according to the embodiment of the present disclosure is a means for suppressing heat generation due to friction generated between air and a rotating body, and the mechanism by which heat is generated is fundamentally different from friction between solids, such as in bearings.

[0021] Here, we will discuss the specific differences between frictional heat generated between air and a rotating solid (air-solid) and between a solid and a rotating solid (solid-solid). Heat generated by friction between air and a solid occurs when the surface of the solid and the air molecules become attracted to each other due to friction, increasing the internal energy of the solid and releasing it as thermal energy. Furthermore, because air has low thermal conductivity and heat does not easily transfer from the solid to the air, the heat generated by friction does not spread from the solid to the air, but remains on the surface of the solid. For these reasons, heat generated on the surface of a rotating solid has a significant impact on the performance of components, and therefore suppressing heat generation on the surface of the solid is significant in improving motor performance.

[0022] On the other hand, heat generation due to friction between solids occurs due to the roughness of the surfaces of the contacting solids and the movement of the solids, such as rolling and sliding. Such movement causes the surfaces of the solids to rub against each other, generating surface friction. As a result, the internal energy between the solids increases due to the friction, and is released as heat energy. Because the thermal conductivity of solids is higher than that of air, the heat generated by friction is distributed relatively evenly among the contacting solids.

[0023] As described above, the heat generation mechanisms differ between air and solid and solid-solid contact, and there is a need to suppress heat generation due to friction with air in magnet shatter prevention protective tubes that are used in a rotating state.

[0024] In contrast, the protective tube according to an embodiment of the present disclosure is made of carbon fiber reinforced resin, and the coefficient of dynamic friction of the outer surface in the direction of rotation against a mirror-finished steel plate is 0.3 or less. By having the coefficient of dynamic friction of the outer surface in the direction of rotation within the above range, heat generation due to friction with the air is suppressed even when used in a rotating situation (e.g., 10,000 rpm or higher). Therefore, heat generation can be suppressed regardless of the material used for the protective tube; for example, heat generation can be suppressed even when the same material as that conventionally used is used. Therefore, while taking full advantage of the advantages of CFRP, the deterioration of mechanical properties due to heat generation is suppressed, and further, because the amount of heat generated is small, the thermal impact on the motor itself can be avoided.

[0025] According to the protective tube of the embodiment of the present disclosure, even in the case of a protective tube that covers the outer surface of a permanent magnet in a permanent magnet synchronous electric motor that rotates particularly at high speed (for example, at a rotational speed of 10,000 rpm or more), heat generation due to friction with the air that accompanies rotation of the motor that rotates in the air is suppressed.

[0026] Dynamic friction coefficient The coefficient of dynamic friction in the direction of rotation of the outer surface of the protective tube is 0.3 or less, and preferably 0.1 or less. If the coefficient of dynamic friction is 0.3 or less, the increase in the surface temperature of the protective tube can be suppressed (for example, kept to around 70°C) even when used in a permanent magnet synchronous electric motor that rotates at a higher speed (for example, a rotational speed of 20,000 rpm). By suppressing the surface temperature to around 70°C, it is possible to keep the temperature below 80°C, which is known as the general heat resistance temperature of CFRP, and therefore it is possible to suppress a deterioration in the mechanical properties of the protective tube.

[0027] Furthermore, if the dynamic friction coefficient is 0.1 or less, the protective tube can be kept in a state where it generates almost no heat (i.e., at a temperature close to room temperature (e.g., 25°C)) even when used in a permanent magnet synchronous electric motor that rotates at a higher speed (e.g., 20,000 rpm). Also, if the dynamic friction coefficient is 0.1 or less, the surface temperature can be kept at around 70°C, even in protective tubes that rotate at 60,000 rpm, which is expected to be developed in the future, and deterioration of the mechanical properties of the protective tube can be suppressed.

[0028] On the other hand, the lower limit of the dynamic friction coefficient is not particularly limited, and in the present technology, it is most preferable that the dynamic friction coefficient is 0. However, from the viewpoint of feasibility, it is preferable that the dynamic friction coefficient is 0.001 or more, and more preferably 0.01 or more.

[0029] Here, the dynamic friction coefficient is measured in accordance with JIS K 7125. Although it is difficult to measure the dynamic friction coefficient between air and a solid, the inventors have discovered that by using a mirror-finished steel plate as the sliding piece, it is possible to calculate a dynamic friction coefficient that is highly correlated with heat generation due to friction between air and a solid.

[0030] First, as shown in Figure 2, measurement samples 20a, 20b, and 20c were cut out into 30 mm long x 15 mm wide pieces with the rotation direction Y of the magnet shatterproof protective tube 13 as the longitudinal direction. A 10 mm x 10 mm x 7 mm thick, mirror-finished steel plate was used as a sliding piece, placed on the measurement sample with the mirror-finished surface facing down, and the sample was pulled using a friction coefficient measurement jig at a tensile tester with a pulling speed of 1000 mm / min at room temperature (25°C). An example of a friction coefficient measurement jig that can be used is the shield-type COF-10N-V manufactured by Imada Co., Ltd. When using the shield-type COF-10N-V, the sliding piece is attached to the back of the clamping jig included with the COF-10N-V, and the kinetic friction coefficient is measured by pulling the wire attached to the pulley with the tensile tester. The static friction force peaks were excluded from the load peaks obtained, and the average value after the relative motion between the contact surfaces began was used as the kinetic friction force D [N]. Then, the dynamic friction coefficient μ is calculated from the dynamic friction force using the following formula (1): D The process from removing the peak of static friction force to calculating the coefficient of dynamic friction can be performed automatically using the accompanying software manufactured by Imada Co., Ltd. μ D =D / 1.96…Equation (1) This procedure is repeated three times for each of the three measurement samples, and the average value is taken as the dynamic friction coefficient of the protective tube. The three measurement samples are preferably collected consecutively with the rotation direction Y as the longitudinal direction, as shown in Figure 2 for measurement samples 20a, 20b, and 20c.

[0031] The mirror finish on the sliding piece is carried out as follows: First, a steel plate cut to 10 mm x 10 mm x 7 mm thick is polished using SIC abrasive paper #1000. Next, a 1 μm diamond cut polisher is used to perform mirror buff polishing. After that, 0.06 μm colloidal silica is used to perform mirror buff polishing. Finally, the sliding piece is obtained by checking under a microscope that there are no polishing scratches.

[0032] The protective tube can be produced, for example, by a sheet winding method to obtain a cylindrical CFRP.

[0033] The following method is an effective example of a method for controlling the dynamic friction coefficient of the protective tube's surface within the aforementioned range. One method is to polish the surface of the CFRP after heat curing with abrasive paper of #1000 or higher. In order to reduce the dynamic friction coefficient, it is effective to polish only the resin on the surface of the CFRP. This is because if polishing is performed deeper than the surface, the fibers in the CFRP will become frayed, which will actually increase the dynamic friction coefficient on the surface.

[0034] The method for controlling the dynamic friction coefficient of the outer peripheral surface of the protective tube within the aforementioned range is not limited to the method using abrasive paper as described above. For example, dry or wet polishing using a dry or wet polisher of #1000 or larger is also effective. Other control methods include applying a coating with a low dynamic friction coefficient to the surface of the cured CFRP, and plating the surface of the CFRP to reduce the dynamic friction coefficient.

[0035] Protective tube shape The protective tube is cylindrical in shape and is provided to cover the outer peripheral surface of the permanent magnet in the permanent magnet synchronous electric motor. The protective tube rotates in a direction that aligns with the central axis of the cylinder.

[0036] Protective tube material The protective tube is made of carbon fiber reinforced plastic (CFRP) using carbon fiber as the reinforcing fiber. The type of carbon fiber can be, for example, either PAN-based or pitch-based, and can be selected depending on the purpose and application. The form of the carbon fiber is not particularly limited, and it can be short or long fiber. Examples of reinforcing fiber substrates that can be used as the carbon fiber substrate include nonwoven fabric substrates using chopped fiber, tow using continuous fiber, cloth materials with a cloth-like form, and unidirectional reinforcing fiber substrates (UD materials). From the perspective of improving the mechanical properties of the protective tube, it is preferable to use long unidirectional carbon fiber in which the fiber axis is oriented parallel to the rotation direction.

[0037] A fiber-reinforced resin is a resin material containing a matrix resin and a reinforcing fiber material, with the reinforcing fiber material held within the matrix resin. The term "held" refers to a state in which the reinforcing fiber material is composited with the matrix resin. Specifically, this refers to a state in which the reinforcing fiber material is dispersed within the matrix resin, a state in which fibers arranged with directionality are impregnated with resin, or a state in which continuous fibers are bundled together with resin. However, the form is not particularly limited and can be appropriately determined depending on the length and directionality of the fibers, the ratio of fibers in the resin, and the like. The matrix resin contains at least one of a curable resin and a thermoplastic resin.

[0038] The carbon fiber reinforced resin is not particularly limited, but from the viewpoint of easily increasing rigidity, the tensile modulus is preferably in the range of 100 GPa to 160 GPa, and more preferably 125 GPa to 160 GPa.

[0039] <Permanent magnet synchronous electric motor and rotor> A permanent magnet synchronous electric motor according to an embodiment of the present disclosure has a rotor according to an embodiment of the present disclosure shown below.

[0040] A rotor according to an embodiment of the present disclosure includes a rotor shaft, a permanent magnet attached to the outer peripheral surface of the rotor shaft, and a magnet scattering prevention protective tube according to an embodiment of the present disclosure that covers the entire outer peripheral surface of the permanent magnet.

[0041] Here, an example of the rotor configuration will be described with reference to FIG.

[0042] Fig. 1 is a schematic cross-sectional view showing the configuration of a rotor. The rotor 10 shown in Fig. 1 has permanent magnets 12 attached to the outer peripheral surface of a rotor shaft 11, and a protective tube 13 arranged to cover the entire outer peripheral surface of the permanent magnets 12.

[0043] The rotational speed of the rotor in the permanent magnet synchronous electric motor is not particularly limited, but can be, for example, 10,000 rpm or more, 20,000 rpm or more, or 60,000 rpm or more.

[0044] The protective tube may be a single piece or may be divided into multiple pieces. If the protective tube is divided into multiple pieces, it may be divided into two or more pieces in the axial direction or in the rotational direction. If the protective tube is made into one piece without being divided, when placing the protective tube on the rotor shaft to which the permanent magnets are attached, for example, the protective tube is manufactured so that its inner diameter is approximately the same as or slightly smaller than the outer diameter of the rotor shaft to which the permanent magnets are attached. After cooling the rotor shaft to reduce the diameter of the rotor shaft to which the permanent magnets are attached, the manufactured protective tube is fitted, and then the rotor shaft and the protective tube can be integrated by a method such as returning to room temperature and fitting them together.

[0045] If the protective tube is divided into two or more pieces in the direction of rotation to allow for easier fitting to the magnet, it can be installed by, for example, using adhesive to attach the protective tube to the rotor shaft on which the permanent magnet is attached. 4, the protective tube 3 may be divided in the axial direction X, and may be made up of, for example, six members 3a to 3f. When the protective tube 3 is divided into multiple members in the axial direction X, when the protective tube 3 is disposed on the rotor shaft 1 to which permanent magnets (not shown) are affixed, the members 3a to 3f constituting the protective tube 3 are manufactured so that the inner diameter of each of the members 3a to 3f is approximately the same as or slightly smaller than the outer diameter of the rotor shaft 1 to which the permanent magnets are affixed. After cooling the rotor shaft 1 to reduce the diameter of the rotor shaft 1 to which the permanent magnets are affixed, the manufactured members 3a to 3f are fitted in, and then the rotor shaft 1 and the members 3a to 3f of the protective tube 3 may be integrated in this manner.

[0046] Even if the protective tube is divided into multiple parts in the axial or rotational direction, the same effect can be obtained as long as the dynamic friction coefficient of the surface of each tube is within the above-mentioned range, because it is the dynamic friction coefficient of each tube that affects the dynamic friction force in the rotational direction. [Example]

[0047] The effects of the present disclosure will be specifically explained below using examples, but the present disclosure is not limited to these examples.

[0048] Example 1 A unidirectional carbon fiber reinforced epoxy prepreg (Toray, PN10766754) with a fiber volume content of 60% was wrapped around a Φ58mm x 100mm mandrel so that the fiber orientation was longitudinal, forming a cylindrical shape. A fluorine-based heat-shrinkable tube was placed over it and heated at 130°C for 1 hour. The mandrel and heat-shrinkable tube were then removed to produce a CFRP tube with an outer diameter of 60mm, an inner diameter of 58mm, and a length of 10mm. The surface of the CFRP was then polished with #3000 abrasive paper to remove only the surface resin, resulting in a magnet shatterproof protective tube A1.

[0049] Three measurement samples 20a, 20b, and 20c measuring 30 mm x 15 mm were taken from the obtained magnet scattering prevention protective tube A1 as shown in Figure 2. The dynamic friction coefficient of these measurement samples was measured using the method described above and found to be 0.3.

[0050] Furthermore, as shown in Figure 3, a thermocouple 30 was attached to the surface of the magnet scattering prevention protective tube 13, and a rotation test was conducted in an air environment at 25°C, in which the magnet scattering prevention protective tube was rotated at 10,000 rpm around a central axis 40 passing through the longitudinal direction of the magnet scattering prevention protective tube. The surface temperature was measured one hour after the start of rotation and was 25°C. This indicates that the magnet scattering prevention protective tube was not generating heat. The rotation speed was also changed to 20,000 rpm and 60,000 rpm, and the surface temperature was measured one hour after the start of rotation in the same manner. The temperature was 61°C at 20,000 rpm and 219°C at 60,000 rpm.

[0051] Example 2 A magnet scattering prevention protective tube A2 was obtained in the same manner as in Example 1, except that the abrasive paper used in manufacturing the magnet scattering prevention protective tube was changed to #10000 abrasive paper, and a magnet scattering prevention protective tube with a dynamic friction coefficient of 0.1 was obtained.

[0052] Similar to Example 1, a rotation test was conducted at rotation speeds of 20,000 rpm and 60,000 rpm. The surface temperature was measured one hour after the start of rotation and was 25°C (at 20,000 rpm), indicating that the magnet shatter prevention protective tube was not generating heat. At 60,000 rpm, the temperature was 78°C.

[0053] (Comparative Example 1) A magnet scattering prevention protective tube B1 was obtained in the same manner as in Example 1, except that no polishing with abrasive paper was performed during the production of the magnet scattering prevention protective tube, and a magnet scattering prevention protective tube with a dynamic friction coefficient of 0.4 was obtained.

[0054] A rotation test was carried out at rotation speeds of 10,000 rpm, 20,000 rpm, and 60,000 rpm in the same manner as in Example 1. The surface temperature was measured one hour after the start of rotation and was 36°C at 10,000 rpm, 80°C at 20,000 rpm, and 290°C at 60,000 rpm.

[0055] [Table 1]

[0056] The typical heat resistance temperature of CFRP is about 80°C, and the typical heat resistance temperature of heat-resistant CFRP is about 200°C to 250°C.

[0057] As shown in Table 1, the protective tubes of Examples 1 and 2, in which the coefficient of dynamic friction in the direction of rotation of the outer surface is 0.3 or less, show reduced heat generation due to friction with the air as the tube rotates, compared to the protective tube of Comparative Example 1, in which the coefficient of dynamic friction exceeds 0.3. [Explanation of symbols]

[0058] 1, 11 Rotor shaft 3, 13 Protection tube (magnetic scattering prevention protection tube) 3a, 3b, 3c, 3d, 3e, 3f parts 10 rotor 12 Permanent magnets 20a, 20b, 20c Measurement samples 30 Thermocouple 40 center axis X-axis direction Y rotation direction

Claims

1. A cylindrical magnet scattering prevention protective tube that covers the outer peripheral surface of a permanent magnet in a permanent magnet synchronous electric motor, Made of carbon fiber reinforced resin, The coefficient of dynamic friction in the rotational direction of the outer surface against a mirror-finished steel plate is 0.3 or less. Protective tube to prevent magnet scattering.

2. 2. The magnet scattering prevention protective tube according to claim 1, wherein the dynamic friction coefficient is 0.1 or less.

3. 2. The magnet scattering prevention protective tube according to claim 1, wherein the cylindrical magnet scattering prevention protective tube is divided into two or more sections in the axial direction or the rotational direction.

4. A rotor shaft; a permanent magnet attached to the outer peripheral surface of the rotor shaft; The magnet scattering prevention protective tube according to any one of claims 1 to 3, which covers the entire outer peripheral surface of the permanent magnet; A rotor of a permanent magnet synchronous electric motor having:

5. 5. The rotor of a permanent magnet synchronous electric motor according to claim 4, which rotates at 10,000 rpm or more in the permanent magnet synchronous electric motor.

6. A permanent magnet synchronous electric motor having the rotor of claim 4.

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