Rotary member

Abstract

To provide a rotary member that is lightweight yet has high tensile strength.SOLUTION: A rotary member 2, which rotates at high speed, is a carbon fiber reinforced molding using composite carbon fibers of a composite fiber bundle 10 as reinforcing fibers. The composite carbon fiber has a structure made up of multiple carbon nanotubes formed on a surface of the carbon fibers that make it up. The carbon nanotubes have a curved shape. The carbon nanotubes adhere to a curved surface of the carbon fiber in various orientations to form the structure. The rotary member 2 has a helical layer 6 in which the composite carbon fibers are oriented at an inclination angle of 40° to 80° relative to an axial direction thereof, and a hoop layer 7 in which the composite carbon fibers are oriented in a direction that is approximately perpendicular to the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rotating member. [Background technology]

[0002] Known rotating members that rotate at high speed include those fitted onto the rotor of a surface permanent magnet motor or a generator with a similar structure (hereinafter referred to as a surface permanent magnet motor, etc.) (see, for example, Patent Document 1). The rotor of a surface permanent magnet motor or the like incorporates multiple permanent magnets on its outer circumferential surface, and the rotor is press-fitted into the hollow interior of the rotating member to prevent the permanent magnets from peeling off from the rotor and scattering due to centrifugal force. Because the rotating member is subject to a force from the permanent magnets directed radially outward, the rotating member is required to have high tensile strength in the circumferential direction. Furthermore, centrifugal force also acts on the mass of the rotating member itself. For this reason, rotating members made of carbon fiber-reinforced plastic, in which carbon fiber is used as the reinforcing fiber, are also known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-319581 Summary of the Invention [Problem to be solved by the invention]

[0004] In the surface permanent magnet motors described above, the magnetic air gap of the rotating members increases by at least the thickness of the rotating members, which reduces the magnetic flux density and efficiency. For this reason, rotating members of surface permanent magnet motors and the like are required to be not only lightweight but also thin and have sufficient strength. While it is useful to use rotating members made of carbon fiber reinforced plastics as such rotating members, rotating members with smaller thicknesses and higher tensile strength are desired.

[0005] An object of the present invention is to provide a rotating member that is lightweight yet has higher tensile strength. [Means for solving the problem]

[0006] The rotating member of the present invention is a carbon fiber reinforced molded body in which carbon fibers are embedded in a matrix resin, and is a rotating member that rotates integrally with the rotating body of an electric motor or generator.The rotating member has a helical layer in which composite carbon fibers are oriented at an inclination angle of 40° or more and 80° or less with respect to the axial direction of the rotating member, and a hoop layer in which composite carbon fibers are oriented in a direction approximately perpendicular to the axial direction of the rotating member.The composite carbon fiber is provided on the surface of the carbon fiber and has a structure composed of a plurality of carbon nanotubes with a bent shape having bent portions, forming a network structure with contact portions where the carbon nanotubes are in direct contact with each other, and a sizing agent that crosslinks the carbon nanotubes that are in direct contact with each other. [Effects of the Invention]

[0007] According to the present invention, a rotating member can be provided that is lightweight yet has higher tensile strength, as the structure comprises carbon fibers having carbon nanotube structures formed on the surface thereof embedded in a matrix resin, and a helical layer and a hoop layer in which the composite carbon fibers are oriented at a predetermined inclination angle relative to the axial direction of the rotating member. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram showing the configuration of a main part of a surface permanent magnet type electric motor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a partial cross-sectional view schematically showing a helical layer and a hoop layer in a rotating member. [Figure 3] FIG. 2 is a partial cross-sectional view schematically showing the orientation of composite fiber bundles in a helical layer. [Figure 4] FIG. 2 is a partial cross-sectional view schematically showing the orientation of composite fiber bundles in a hoop layer. [Figure 5] FIG. 2 is an explanatory diagram showing the configuration of a composite fiber bundle. [Figure 6]FIG. 2 is an explanatory diagram showing the state of adhesion of a sizing agent to CNTs. [Figure 7] FIG. 2 is an explanatory diagram showing the state of adhesion of a sizing agent at a contact portion where CNTs are in contact with each other. [Figure 8] FIG. 10 is an explanatory diagram showing another state in which a sizing agent is attached to CNTs. [Figure 9] FIG. 10 is an explanatory diagram showing another state in which a sizing agent is attached to a contact portion where CNTs are in contact with each other. [Figure 10] 1A to 1C are explanatory views showing an outline of a procedure for producing a rotating member. [Figure 11] FIG. 1 is an explanatory diagram showing the configuration of an attachment device for attaching CNTs to carbon fibers. [Figure 12] FIG. 1 is a perspective view showing an example of a filament winder. [Figure 13] FIG. 2 is an explanatory diagram illustrating an example of a resin applying device. [Figure 14] 10 is a graph showing an example in which the heating temperature is changed stepwise when curing a matrix resin. [Figure 15] FIG. 2 is an explanatory diagram showing a state in which carbon fibers are cross-linked to each other. [Figure 16] 1 is an SEM photograph of a cross section of a rotating member showing the state of composite fibers in the rotating member. [Figure 17] 1 is an SEM photograph of a cross section of a rotating member using carbon fiber raw yarn, showing the state of carbon fibers in the rotating member. [Figure 18] 1 is a SEM photograph showing the bent state of the CNT material used in the examples. [Figure 19] 1 is a graph showing the results of a NOL ring test in Example 1 and Comparative Example 1. [Figure 20] 1 is a graph showing an enlarged view of the region where the fiber volume content is 60% or more in the results of the NOL ring test in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 shows a rotating member 2 according to an embodiment. A plurality of rotating members 2 are provided as scattering prevention members for a surface-mounted permanent magnet motor 3. Each rotating member 2 is ring-shaped (cylindrical) and narrow (short in the direction of the axis 2a of the rotating member 2). The rotating members 2 are fitted around the rotor 4, which is a rotating body, so as to be aligned along the axis (rotation center axis) of the rotor 4. Each rotating member 2 is a sleeve into which the rotor 4 is press-fitted and fixed, and rotates integrally with the rotor 4. Therefore, the rotating member 2 rotates in its circumferential direction. A plurality of permanent magnets 5 are embedded in the outer peripheral surface of the rotor 4 at predetermined intervals along the circumferential direction of the rotor 4. The rotating member 2 holds the permanent magnets 5 against centrifugal force to prevent them from peeling off and scattering radially outward from the rotor 4 when the rotor 4 rotates at high speed.

[0010] As shown schematically in FIG. 2, the rotating member 2 is a carbon fiber reinforced molding (carbon fiber reinforced plastic) composed of a composite fiber bundle 10 and a matrix resin M in which carbon fibers 12 (see FIG. 5) of composite fibers 11 (see FIG. 5) constituting the composite fiber bundle 10 are embedded. The composite fiber bundle 10 is wound in the circumferential direction of the rotating member 2. "Wound in the circumferential direction of the rotating member 2" means that the composite fiber bundle 10 has a component along the circumferential direction of the rotating member 2. The rotating member 2 is composed of a helical layer 6 and a hoop layer 7 formed on the outer periphery of this helical layer 6. Note that in FIG. 2, for ease of illustration, each of the composite fiber bundles 10 is exaggerated and drawn so that it can be distinguished.

[0011] The helical layer 6 is a layer in which the composite fiber bundle 10 is helically wound, and increases the strength of the rotating member 2 against axial forces and prevents the hoop layer 7 from collapsing when the rotating member 2 is press-fitted into the rotor 4. As shown in FIG. 3 , when the rotating member 2 is viewed from a direction perpendicular to the axial center 2a, the helical layer 6 has the composite fiber bundle 10 oriented at an inclination angle θ1 with respect to the axial center 2a. The composite fiber bundle 10 is oriented clockwise with the inclination angle θ1 and counterclockwise with respect to the axial center 2a. This inclination angle θ1 is the same as the winding angle when the rotating member 2 is manufactured. Here, the inclination angle θ1 of the helical winding is within a range of 40° to 80°. In this example, the inclination angle θ1 is 40°.

[0012] Hereinafter, when distinguishing between helical layers 6 in which the composite fiber bundles 10 are inclined clockwise and counterclockwise, the angle will be denoted by a positive or negative sign depending on the direction of inclination relative to the axis 2a. When distinguishing similarly for the hoop layers 7, the angle will be denoted by a positive or negative sign.

[0013] In the helical layer 6, if a layer consisting of one layer of composite fiber bundles 10 wound (disposed) closely together in the axial direction of the rotating member 2 with an inclination angle of +θ1 and one layer of composite fiber bundles 10 wound closely together with an inclination angle of -θ1 is defined as a helical unit layer, the helical layer 6 is composed of one or more helical unit layers. The helical unit layer includes a portion where a composite fiber bundle 10 with an inclination angle of +θ1 and a composite fiber bundle 10 with an inclination angle of -θ1 intersect. When the helical layer 6 is composed of multiple helical unit layers, they are layered in the radial direction of the rotating member 2. Note that the smaller the inclination angle θ1, the smaller the contribution of the helical layer 6 to improving strength against radial or circumferential forces.

[0014] The hoop layer 7 is a layer in which the composite fiber bundles 10 are hoop-wound, and it is essentially this hoop layer 7 that provides the rotating member 2 with high strength in the radial and circumferential directions. As shown in Figure 4, in this hoop layer 7, when the rotating member 2 is viewed from a direction perpendicular to the axis 2a, the composite fiber bundles 10 are oriented at an inclination angle θ2 that is approximately perpendicular to the axis 2a. Here, "approximately perpendicular" means that the inclination angle θ2 is within a range of 85° to 90°. Strictly speaking, the composite fiber bundles 10 of the hoop layer 7 may be oriented clockwise with respect to the axis 2a at the inclination angle θ2, or may be oriented counterclockwise with respect to the axis 2a at the inclination angle θ2.

[0015] In the hoop layer 7, if a layer made of composite fiber bundles 10 with an inclination angle θ2 wound (arranged) without gaps in the axial direction of the rotating member 2 is defined as a hoop unit layer, the hoop layer 7 is composed of two or more hoop unit layers. In the hoop unit layer, there is no portion where composite fiber bundles 10 with opposite positive and negative inclination angles θ2 intersect. In the hoop layer 7, hoop unit layers of composite fiber bundles 10 oriented with an inclination angle of +θ2 and hoop unit layers of composite fiber bundles 10 oriented with an inclination angle of -θ2 are alternately layered in the radial direction of the rotating member 2.

[0016] The thickness D1 of the helical layer 6 is adjusted by increasing or decreasing the number of helical unit layers. Similarly, the thickness D2 of the hoop layer 7 is adjusted by increasing or decreasing the number of hoop unit layers. The thickness of the rotating member 2 is the sum of the thicknesses of the helical layer 6 and the hoop layer 7 (= D1 + D2).

[0017] In order to obtain higher strength against radial or circumferential forces while maintaining a predetermined strength in the axial direction, the thickness ratio (D2 / D1) of the thickness D1 of the helical layer 6 to the thickness D2 of the hoop layer 7 is preferably set within a range of 5 to 20. If the thickness ratio (D2 / D1) is 5 or more, the required strength can be obtained while effectively suppressing the thickness of the rotating member 2. Furthermore, if the thickness ratio (D2 / D1) is 20 or less, the strength required to fit the rotating member 2 into the rotor 4 can be further increased, and the possibility of breakage can be sufficiently reduced.

[0018] Furthermore, if the thickness D1 of the helical layer 6 is at a certain level, the strength of the rotating member 2 required for press-fitting into the rotor 4 is obtained, and if the thickness D2 of the hoop layer 7 is at a certain level or above, the inner diameter of the rotating member 2 expands due to the crushing of the hoop layer 7, which facilitates press-fitting. For this reason, the upper limit of the thickness D1 of the helical layer 6 is preferably set to 600 μm, and more preferably to 350 μm. In other words, if the thickness D1 of the helical layer 6 based on the above thickness ratio to the thickness D2 of the hoop layer 7 exceeds the upper limit, it is preferable to set the thickness D1 to the upper limit.

[0019] In this example, the thickness of the rotating member 2 is 1.83 mm, and the thickness ratio is 5.1. That is, the thickness D1 of the helical layer 6 is 0.3 mm, and the thickness D2 of the hoop layer 7 is 1.53 mm.

[0020] [Composite fiber bundle] In Figure 5, a composite fiber bundle 10 is a bundle of multiple composite fibers 11. Each composite fiber 11 has a carbon fiber 12 and a structure 14 formed on the surface of the carbon fiber 12, and a sizing agent 15 (see Figure 6) is applied to the structure 14. The structure 14 is made up of multiple carbon nanotubes (hereinafter referred to as CNTs) 17 entangled with each other. For ease of illustration, only a dozen or so composite fibers 11 are depicted in Figure 5.

[0021] The composite fiber bundle 10 is, for example, 12K, i.e., composed of 12,000 composite fibers 11. The number of composite fibers 11 constituting the composite fiber bundle 10 is not particularly limited, but can be, for example, within a range of 10,000 to 100,000. In the composite fiber bundle 10, it is preferable that the composite fibers 11 are not substantially entangled with each other and that the fiber axis direction of each composite fiber 11 is aligned. The fiber axis direction is the axial direction (extension direction) of the composite fibers 11 or the carbon fibers 12.

[0022] Furthermore, in a carbon fiber bundle 18 (see FIG. 11 ) obtained by bundling together carbon fibers 12 that are raw yarns used in producing the composite fiber bundle 10, it is preferable that the carbon fibers 12 are not substantially entangled with one another and that the fiber axis direction of each carbon fiber 12 is aligned. A carbon fiber bundle 18 in which the carbon fibers 12 are substantially not entangled with one another or are less entangled with one another makes it easier to uniformly spread the carbon fibers 12. This makes it easier to uniformly attach CNTs 17 to each carbon fiber 12 that is the raw yarn, and in the composite fiber bundle 10, the matrix resin M is uniformly impregnated into the composite fiber bundle 10, allowing each of the composite fibers 11 to contribute to the strength.

[0023] The entanglement of the carbon fibers 12 in the carbon fiber bundle can be evaluated based on the degree of disorder of the carbon fibers 12. For example, the carbon fiber bundle is observed at a certain magnification using a scanning electron microscope (SEM), and the lengths of a predetermined number (e.g., 10) of carbon fibers 12 in the observed range (a predetermined length range of the carbon fiber bundle) are measured. The degree of disorder of the carbon fibers 12 can be evaluated based on the length variation, the difference between the maximum and minimum values, and the standard deviation for the predetermined number of carbon fibers 12 obtained from the measurement results. Furthermore, whether the carbon fibers 12 are substantially entangled can also be determined by measuring the degree of entanglement in accordance with the entanglement measurement method of JIS L1013:2010 "Testing Methods for Chemical Fiber Filament Yarns." The smaller the measured degree of entanglement, the less entanglement of the carbon fibers 12 in the carbon fiber bundle. The entanglement of the composite fibers 11 in the composite fiber bundle 10 can also be evaluated in a similar manner.

[0024] The carbon fibers 12 are not particularly limited, and may be PAN-based or pitch-based fibers obtained by burning organic fibers derived from petroleum, coal, or coal tar, such as polyacrylonitrile, rayon, or pitch, or fibers obtained by burning organic fibers derived from wood or plant fibers. Commercially available carbon fibers may also be used. The diameter and length of the carbon fibers 12 are also not particularly limited. Carbon fibers 12 having a diameter of approximately 5 μm to 20 μm are preferably used, and those having a diameter of 5 μm to 10 μm are more preferably used. Long carbon fibers 12 are preferably used, and their length is preferably 50 m or more, more preferably 100 m to 100,000 m, and even more preferably 100 m to 10,000 m. When used to form the rotating member 2, the carbon fibers 12 may be cut into short lengths.

[0025] As described above, a structure 14 is formed on the surface of the carbon fiber 12. The structure 14 is formed by entangling a plurality of CNTs 17. The CNTs 17 that make up the structure 14 are uniformly dispersed and entangled over almost the entire surface of the carbon fiber 12, forming a network structure in which a plurality of CNTs 17 are connected in an entangled state. The connection here includes physical connection (simple contact) and chemical connection. The CNTs 17 are in direct contact with each other without the presence of an intervening agent such as a surfactant or an adhesive between them.

[0026] Some of the CNTs 17 that make up the structure 14 are directly attached and fixed to the surface of the carbon fiber 12. This causes the structure 14 to be directly attached to the surface of the carbon fiber 12. Direct attachment of the CNTs 17 to the surface of the carbon fiber 12 means that the CNTs 17 are directly attached to the carbon fiber 12 without any dispersant such as a surfactant, adhesive, or the like intervening between the CNTs 17 and the surface of the carbon fiber 12. Because some of the CNTs 17 that make up the structure 14 are directly attached to the surface of the carbon fiber 12, the structure 14 is in direct contact with the surface of the carbon fiber 12 without any dispersant, adhesive, or the like intervening.

[0027] Furthermore, some of the CNTs 17 constituting the structure 14 are not in direct contact with the surface of the carbon fiber 12, but are fixed to the carbon fiber 12 by being entangled with other CNTs 17. Furthermore, some are directly attached to the surface of the carbon fiber 12 and are fixed to the carbon fiber 12 by being entangled with other CNTs 17. Hereinafter, these fixations of CNTs 17 to carbon fiber 12 will be collectively referred to as "adhesion to carbon fiber 12." Note that the state in which CNTs 17 are entangled or intertwined includes a state in which a part of a CNT 17 is pressed against another CNT 17. The adhesion (fixation) between CNTs 17 and between CNTs 17 and carbon fiber 12 is due to bonds caused by van der Waals forces, hydrogen bonds, etc.

[0028] The CNTs 17 constituting the structure 14 include those that are directly attached to the surface of the carbon fibers 12 as described above, as well as those that are not in direct contact with the surface of the carbon fibers 12 but are fixed to the carbon fibers 12 by being entangled with other CNTs 17. Therefore, the structure 14 in this example is composed of more CNTs 17 than conventional composite fiber structures that are composed only of CNTs that are directly attached to the surface of the carbon fibers. In other words, the number of CNTs 17 attached to the carbon fibers 12 is greater than in conventional structures.

[0029] As described above, the plurality of CNTs 17 are connected to each other without any inclusions on their surfaces to form the structure 14, so the composite fiber 11 exhibits the electrical and thermal conductivity properties inherent to the CNTs. Furthermore, because the CNTs 17 are attached to the surfaces of the carbon fibers 12 without any inclusions, the CNTs 17 that form the structure 14 are less likely to peel off from the surfaces of the carbon fibers 12, and the rotating member 2 that includes the composite fibers 11 has improved mechanical strength, including tensile strength.

[0030] As described above, in the rotating member 2, the composite fiber bundle 10, which is made up of a plurality of composite fibers 11 on which structures 14 are formed, is impregnated with and cured by the matrix resin M. Because the structures 14 are impregnated with and cured in this manner, the structures 14 on each carbon fiber 12 are fixed to the matrix resin M together with the surfaces of the carbon fibers 12. As a result, each composite fiber 11 is in a state in which the carbon fibers 12 are firmly bonded to the matrix resin M, i.e., the interfacial adhesive strength between the carbon fibers 12 and the matrix resin M is high, and the tensile strength of the rotating member 2 is high.

[0031] As will be described later, by forming the CNTs 17 in a curved shape, a larger number of CNTs 17 are attached to the carbon fibers 12 than when straight CNTs are used, resulting in a structure 14 that is thicker and has the CNTs 17 woven together like the fibers of a nonwoven fabric. Around each carbon fiber 12 of the rotating member 2, a region 19 (hereinafter referred to as a composite region) (see FIG. 15 ) is formed in which the structure 14 is impregnated with a matrix resin M and hardened. The formation of such a composite region 19 increases the interfacial adhesive strength between the carbon fibers 12 and the matrix resin M, thereby increasing the tensile strength of the rotating member 2. Furthermore, the presence of CNTs 17 in the resin portions between adjacent carbon fibers 12 strengthens the interaction between the carbon fibers. This strengthens the strength reduction caused by defects in the carbon fibers 12, as the adjacent carbon fibers 12 support the strength reduction caused by defects in the carbon fibers 12.

[0032] In addition, the properties of the carbon fiber reinforced molded body (rotating member 2) that are improved by attaching CNTs 17 to the surface of the carbon fibers 12 and forming a thick nonwoven fabric-like structure 14 include, in addition to tensile strength, elastic modulus, vibration damping characteristics (vibration control properties), durability against repeated bending, etc.

[0033] The structures 14 formed on each of the multiple carbon fibers 12 are independent structures, and the structures 14 on one carbon fiber 12 and the structures 14 on other carbon fibers 12 do not share the same CNTs 17. In other words, the CNTs 17 included in the structures 14 provided on one carbon fiber 12 are not included in the structures 14 provided on other carbon fibers 12.

[0034] As shown in Fig. 6, sizing agent 15 is applied to CNTs 17 in a state in which it wraps around and covers the contact areas where CNTs 17 are in direct contact with each other. This sizing agent 15 fixes CNTs 17 at the contact areas where they are in direct contact with each other. CNTs 17 at the contact areas are fixed by sizing agent 15 in a state in which they are maintained in direct contact with each other, as shown in Fig. 7.

[0035] As the sizing agent 15, a thermosetting resin or a cured product of a reactive resin having a structure formed by reacting with functional groups present on the surface of the CNTs 17 is preferably used. A reactive resin is a resin having highly reactive functional groups. Examples of reactive resins include an isocyanate compound that forms a sizing agent 15 having an isocyanate-derived structure formed by the reaction of an isocyanate group, and a carbodiimide compound that forms a sizing agent 15 having a carbodiimide-derived structure formed by the reaction of a carbodiimide group. When a reactive resin is used, the method of imparting functional groups to the surface of the CNTs 17 is not particularly limited. The functional groups may be imparted as a result of various treatments performed after the production of the CNTs 17, or may be imparted by a functional group imparting treatment.

[0036] As described above, the sizing agent 15 fixes the contacting CNTs 17 that make up the structure 14 together, thereby strengthening the adhesion between the CNTs 17 and making the structure 14 less likely to collapse.

[0037] 6, the sizing agent 15 is attached to the carbon fibers 12 and the CNTs 17 in a state where it wraps around and covers the contact portions of the CNTs 17 that are in direct contact with the carbon fibers 12. The sizing agent 15 fixes the carbon fibers 12 and the CNTs 17 together, just as it does between CNTs 17. In this way, the sizing agent 15 fixes the carbon fibers 12 and the CNTs 17, thereby making the state in which the CNTs 17 are attached to the carbon fibers 12 stronger and making it difficult for the structure 14 to peel off from the carbon fibers 12.

[0038] The sizing agent 15 prevents the structure 14 from falling off from the carbon fiber 12 and the CNTs 17 from falling off from the structure 14 during the production of the composite fiber bundle 10 or the rotating member 2, thereby preventing a decrease in the interfacial adhesive strength and, ultimately, a decrease in the properties of the rotating member 2, including the tensile strength, and achieving uniform, desirable properties.

[0039] As long as direct contact between the CNTs 17 is maintained and the CNTs 17 are fixed by the sizing agent 15 around the contact area, the CNTs 17 may be wrapped and covered by the sizing agent 15 as described above, or may not be wrapped and covered as shown in Figures 8 and 9. Similarly, as long as direct contact between the carbon fiber 12 and the CNTs 17 is maintained and the carbon fiber 12 and the CNTs 17 are fixed by the sizing agent 15 around the contact area, the CNTs 17 may not be wrapped and covered by the sizing agent 15 as shown in Figure 8.

[0040] In the structure 14, the CNTs 17 form voids (mesh) 20 that they surround. In order not to prevent the matrix resin M from being impregnated into the structure 14, it is preferable that the sizing agent 15 does not close the voids 20.

[0041] The CNTs 17 attached to the carbon fibers 12 have a bent shape. This bent shape of the CNTs 17 is due to the presence of bent portions (bent portions) due to the presence of five-membered and seven-membered carbon rings, etc., in the graphite structure of the CNTs 17, and is a shape that can be evaluated as being curved, bent, or the like by observation with an SEM. For example, a bent shape of the CNTs 17 means that there is at least one bent portion per average length of the CNTs 17 in the range of use described below. Even if the CNTs 17 are long, they will adhere in various positions to the curved surface of the carbon fibers 12. Furthermore, bent CNTs 17 are likely to form spaces (gaps) between them and the surface of the carbon fibers 12 to which they are attached, or between the attached CNTs 17, and other CNTs 17 will enter these spaces. Therefore, by using CNTs 17 with a curved shape, the number of CNTs 17 attached to carbon fiber 12 (the number of CNTs 17 forming structure 14) increases compared to when CNTs with a highly linear shape are used.

[0042] The length of the CNTs 17 is preferably within the range of 0.1 μm or more and 10 μm or less. If the length of the CNTs 17 is 0.1 μm or more, the CNTs 17 can be entangled and directly contact or directly connected to each other to more reliably form structures 14, and as described above, spaces into which other CNTs 17 can enter can be more reliably formed. Furthermore, if the length of the CNTs 17 is 10 μm or less, the CNTs 17 will not adhere across carbon fibers 12. In other words, as described above, the CNTs 17 included in the structures 14 provided on one carbon fiber 12 will not be included in the structures 14 provided on another carbon fiber 12.

[0043] The length of the CNTs 17 is more preferably in the range of 0.2 μm or more and 5 μm or less. If the length of the CNTs 17 is 0.2 μm or more, the number of attached CNTs 17 can be increased to make the structure 14 thicker, and if the length is 5 μm or less, the CNTs 17 are less likely to aggregate when attached to the carbon fibers 12, and are more likely to be dispersed more evenly. As a result, the CNTs 17 are attached to the carbon fibers 12 more uniformly.

[0044] It is not excluded that highly linear CNTs or CNTs outside the above-described length range may be mixed as CNTs attached to the carbon fiber 12. Even if mixed, for example, the number of CNTs attached to the carbon fiber 12 can be increased by allowing highly linear CNTs to enter the spaces formed by the CNTs 17.

[0045] The average diameter of the CNTs 17 is preferably in the range of 0.5 nm to 30 nm, more preferably in the range of 3 nm to 10 nm. If the diameter of the CNTs 17 is 30 nm or less, they are highly flexible and easily adhere to the surface of the carbon fiber 12, and are easily entangled with other CNTs 17 and fixed to the carbon fiber 12, further ensuring the formation of the structure 14. Furthermore, if the diameter is 10 nm or less, the bonds between the CNTs 17 constituting the structure 14 are strong. The diameter of the CNTs 17 is a value measured using a transmission electron microscope (TEM) photograph. The CNTs 17 may be single-walled or multi-walled, but multi-walled CNTs are preferred.

[0046] The number of CNTs 17 attached to the carbon fiber 12 can be evaluated by the thickness of the structure 14 (the length in the radial direction of the carbon fiber 12). The thickness of each part of the structure 14 can be obtained, for example, by adhering a part of the structure 14 on the surface of the carbon fiber 12 to cellophane tape or the like, peeling it off, and measuring the cross section of the structure 14 remaining on the surface of the carbon fiber 12 using an SEM or the like. The thickness of the structure 14 is determined by measuring the thickness of the structure 14 at 10 points in the measurement range so as to cover a predetermined length of the measurement range along the fiber axis direction of the carbon fiber 12 approximately evenly. The length of the measurement range is, for example, five times the upper limit of the range of the length of the CNTs 17 described above.

[0047] The average thickness of the structure 14 obtained as described above is in the range of 10 nm to 300 nm, preferably 15 nm to 200 nm, and more preferably 50 nm to 200 nm. If the thickness of the structure 14 is 200 nm or less, the impregnation of the resin between the carbon fibers 12 is better.

[0048] A highly heat-resistant thermosetting resin can be used as the matrix resin M. Examples of the thermosetting resin used for the matrix resin M include epoxy resin, phenol resin, melamine resin, urea resin, thermosetting polyimide, cyanate ester resin, bismaleimide resin, vinyl ester resin, and mixtures of these resins.

[0049] Next, the procedure for producing the rotating member 2 will be described. As shown in FIG. 10, the rotating member 2 is produced through a structure-forming step ST1, a sizing step ST2, and a molding step ST3. In the structure-forming step ST1, CNTs 17 are attached to each of the carbon fibers 12 (raw yarns) of the carbon fiber bundle 18 to form the structure 14. To achieve this, the carbon fiber bundle 18 is immersed in a CNT isolation dispersion (hereinafter simply referred to as a dispersion) in which the CNTs 17 are isolated and dispersed, and mechanical energy is applied to the dispersion. "Isolated and dispersed" refers to a state in which the CNTs 17 are physically separated one by one and dispersed in the dispersion medium without entanglement, and refers to a state in which the proportion of aggregates in which two or more CNTs 17 are aggregated into bundles is 10% or less. Here, if the proportion of aggregates is 10% or more, aggregation of the CNTs 17 in the dispersion medium is promoted, inhibiting adhesion of the CNTs 17 to the carbon fibers 12.

[0050] 11, the attachment device 21 is composed of a CNT attachment tank 22, guide rollers 23 to 26, an ultrasonic generator 27, a traveling mechanism (not shown) for traveling the carbon fiber bundle 18 at a constant speed, etc. A dispersion liquid 28 is contained in the CNT attachment tank 22. The ultrasonic generator 27 applies ultrasonic waves to the dispersion liquid 28 in the CNT attachment tank 22 from below the CNT attachment tank 22.

[0051] Long carbon fiber bundles 18 (for example, about 100 m) without structures 14 formed thereon are continuously supplied to the attachment device 21. The supplied carbon fiber bundles 18 are wound around guide rollers 23 to 26 in order and run at a constant speed by a running mechanism. The attachment device 21 is supplied with carbon fiber bundles 18 in which no tangle-preventing sizing agent is applied to each carbon fiber 12. The tangle-preventing sizing agent referred to here prevents tangles and the like of the carbon fibers 12 and is different from the sizing agent 15 described above.

[0052] The carbon fiber bundles 18 are wound in an open state around guide rollers 23 to 26, which are, for example, flat rollers. Appropriate tension is applied to the carbon fiber bundles 18 wound around the guide rollers 23 to 26, reducing the risk of the carbon fibers 12 becoming entangled. It is preferable that the carbon fiber bundles 18 are wound around the guide rollers 23 to 26 at a smaller winding angle (90° or less).

[0053] Among the guide rollers 23 to 26, the guide rollers 24 and 25 are disposed within the CNT deposition tank 22. As a result, the carbon fiber bundle 18 travels between the guide rollers 24 and 25 in the dispersion liquid 28. The traveling speed of the carbon fiber bundle 18 is preferably set within a range of 0.5 m / min to 100 m / min. The higher the traveling speed of the carbon fiber bundle 18, the more productivity can be improved. The lower the traveling speed, the more effective it is for uniformly attaching the CNTs 17 and for suppressing entanglement between the carbon fibers 12. Furthermore, the less entanglement between the carbon fibers 12, the more uniformly the CNTs 17 can be attached to the carbon fibers 12. If the traveling speed of the carbon fiber bundle 18 is 100 m / min or less, entanglement between the carbon fibers 12 can be more effectively suppressed and the uniformity of the attachment of the CNTs 17 can be further increased. Furthermore, the traveling speed of the carbon fiber bundle 18 is more preferably set within a range of 5 m / min to 50 m / min.

[0054] The ultrasonic generator 27 applies ultrasonic vibrations as mechanical energy to the dispersion liquid 28. This creates a reversible reaction state in the dispersion liquid 28, where the CNTs 17 alternate between a dispersed state in which they are dispersed and an aggregated state in which they are aggregated. When the carbon fiber bundle 18 is passed through the dispersion liquid 28 in this reversible reaction state, the CNTs 17 adhere to each carbon fiber 12 due to van der Waals forces and the like during the transition from the dispersed state to the aggregated state. The mass of the carbon fiber 12 is more than 100,000 times greater than that of the CNTs 17, and the energy required for the attached CNTs 17 to detach is greater than the energy required for ultrasonic vibration. Therefore, once the CNTs 17 are attached to the carbon fibers 12 in the dispersion liquid 28, they do not peel off from the carbon fibers 12 even after the attachment, even with ultrasonic vibration. Note that the mass of each CNT 17 is extremely small, so the CNTs 17 alternate between a dispersed state and an aggregated state due to ultrasonic vibration.

[0055] By repeatedly transitioning from the dispersed state to the aggregated state, many CNTs 17 are attached to each carbon fiber 12, forming structure 14. As described above, by using CNTs 17 with a curved shape, other CNTs 17 enter the spaces formed between the CNTs 17 and the surface of the carbon fiber 12 to which they are attached, or between the attached CNTs 17, and so on, and more CNTs 17 are attached to carbon fiber 12, forming structure 14.

[0056] The frequency of the ultrasonic vibration applied to the dispersion liquid 28 is preferably 40 kHz or more and 950 kHz or less. If the frequency is 40 kHz or more, entanglement of the carbon fibers 12 in the carbon fiber bundles 18 is suppressed. Furthermore, if the frequency is 950 kHz or less, the CNTs 17 adhere well to the carbon fibers 12. In order to further reduce entanglement of the carbon fibers 12, the frequency of the ultrasonic vibration is preferably 100 kHz or more.

[0057] Furthermore, the number of CNTs 17 attached to the carbon fibers 12 is such that the transitions of the CNTs 17 from a dispersed state to an aggregated state are 100,000 or more times, which effectively suppresses entanglement between the carbon fibers 12 and ensures uniformity in the thickness of the structure 14. The maximum number of attached fibers varies depending on the CNT concentration in the dispersion liquid 28, and increases as the CNT concentration in the dispersion liquid 28 increases. However, if the CNT concentration in the dispersion liquid 28 becomes so high that the CNTs 17 cannot be in a dispersed state when ultrasonic vibrations are applied, the CNTs 17 cannot be attached to the carbon fibers 12.

[0058] For this reason, it is preferable to determine the running speed of the carbon fiber bundle 18, the distance over which the carbon fiber bundle 18 runs in the dispersion liquid 28 (the distance between the guide rollers 24, 25), and the frequency of the ultrasonic vibration applied to the dispersion liquid 28 so that the length of time over which the carbon fiber bundle 18 runs in the dispersion liquid 28, i.e., the time over which the carbon fiber bundle 18 runs between the guide rollers 24, 25 (hereinafter referred to as the immersion time), is 100,000 times or more the period of the ultrasonic vibration applied to the dispersion liquid 28. In other words, when the frequency of the ultrasonic vibration is fs (Hz) and the immersion time is Ts (seconds), it is preferable to satisfy "Ts≧100,000 / fs." For example, if the frequency of the ultrasonic vibration is 100 kHz and the distance over which the carbon fiber bundle 18 runs in the dispersion liquid 28 is 0.1 m, the running speed of the carbon fiber bundle 18 may be set to 6 m / min or less. Furthermore, even when the carbon fiber bundle 18 is immersed in the dispersion liquid 28 in multiple batches, the number of attached CNTs 17 can be nearly maximized if the total immersion time is 100,000 times or more the period of the ultrasonic vibration.

[0059] The dispersion liquid 28 is prepared by adding, for example, long CNTs (hereinafter referred to as material CNTs) to a dispersion medium, cutting the material CNTs into CNTs 17 of the desired length using a homogenizer, shear force, ultrasonic disperser, etc., and uniformly dispersing the CNTs 17.

[0060] Examples of the dispersion medium include water, alcohols such as ethanol, methanol, and isopropyl alcohol, organic solvents such as toluene, acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), hexane, normal hexane, ethyl ether, xylene, methyl acetate, and ethyl acetate, and mixtures of these in any proportion. The dispersion liquid 28 does not contain a dispersant or adhesive.

[0061] As described above, the material CNTs that are the source of the curved CNTs 17 have a curved shape. It is preferable that the diameters of the individual material CNTs are uniform. It is preferable that the material CNTs be capable of being isolated and dispersed even if the length of each CNT produced by cutting is large. This facilitates the production of a dispersion 28 in which CNTs 17 that satisfy the length requirements described above are isolated and dispersed.

[0062] In the composite fiber bundle 10 of this example, as described above, the CNTs 17 attached have a curved shape, and therefore other CNTs 17 enter the spaces formed between the CNTs 17 and the surface of the carbon fiber 12 to which they are attached, or between the attached CNTs 17 themselves. As a result, more CNTs 17 are attached to the carbon fiber 12. Furthermore, since the CNTs 17 are firmly attached to the carbon fiber 12 to form the structure 14, the CNTs 17 are less likely to peel off from the carbon fiber 12. Furthermore, the rotating member 2 produced using such a composite fiber bundle 10 has improved properties due to the CNTs 17.

[0063] The concentration of CNTs 17 in the dispersion liquid 28 is preferably in the range of 0.003 wt% to 3 wt%, and more preferably in the range of 0.005 wt% to 0.5 wt%.

[0064] The carbon fiber bundle 18, in which the CNTs 17 are attached to the carbon fibers 12, is dried after being pulled out from the dispersion liquid 28. The dried carbon fiber bundle 18 (hereinafter referred to as the CNT-attached fiber bundle) is subjected to a sizing treatment, whereby the sizing agent 15 is applied to the structure 14.

[0065] In the sizing treatment step ST2, a sizing treatment is performed on the CNT-attached fiber bundle. The sizing treatment includes a step of applying (contacting) a sizing treatment solution to the CNT-attached fiber bundle and a step of drying. The sizing treatment solution can be made by dissolving a resin that will become the sizing agent 15 in a solvent. Depending on the resin, water, alcohol, ketones, and mixtures thereof can be used as the solvent.

[0066] The sizing solution may be applied by any method, such as immersing the CNT-attached fiber bundle in a liquid tank containing the sizing solution, spraying the sizing solution onto the CNT-attached fiber bundle, or applying the sizing solution to the CNT-attached fiber bundle. The sizing solution is applied to the surface of the CNTs 17 while maintaining direct contact between the CNTs 17. The lower the viscosity, the more likely it is to aggregate near the contact points between the CNTs 17 and between the carbon fibers 12 and the CNTs 17. By adjusting the amount of sizing solution applied to the CNT-attached fiber bundle and the concentration of the resin that serves as the sizing agent 15 in the sizing solution, it is possible to prevent the voids 20 of the structure 14 from being blocked.

[0067] The CNT-attached fiber bundle to which the sizing treatment liquid has been applied is dried to obtain a composite fiber bundle 10. Drying after application of the sizing treatment liquid involves evaporating the solvent in the sizing treatment liquid. The drying method can be a known drying method such as leaving the CNT-attached fiber bundle to which the sizing treatment liquid has been applied to dry, blowing a gas such as air onto the CNT-attached fiber bundle, or heating the CNT-attached fiber bundle. Heating may be used in combination with either leaving the fiber bundle to dry or blowing a gas.

[0068] In the molding step ST3, the rotating member 2 is molded by a filament winding method using the composite fiber bundle 10 obtained through the sizing treatment step ST2. As shown in an example in Fig. 12, for example, a plurality of composite fiber bundles 10 are unwound from a creel (yarn supplying device) 31 while being adjusted to a predetermined tension, and the unwound composite fiber bundles 10 are fed to a filament winder 33 via a resin supplying device 32. When the composite fiber bundle 10 passes through the resin supplying device 32, an uncured liquid matrix resin M is applied to the composite carbon fibers. By applying the matrix resin M in this resin supplying device 32, the matrix resin M is impregnated into the structures 14 formed on the surfaces of the carbon fibers 12.

[0069] A mandrel 34 is rotatably set on the filament winder 33. As the mandrel 34 is rotated by the filament winder 33, the composite fiber bundle 10 to which the matrix resin M has been applied is wound around the mandrel 34 while a predetermined tension is applied to the composite fiber bundle 10. The winding position of the composite fiber bundle 10 around the mandrel 34 is determined by a head (not shown) provided on the resin application device 32. A traverse mechanism T reciprocates the resin application device 32 in the axial direction of the mandrel 34 in synchronization with the rotation of the mandrel 34. As a result, the composite fiber bundle 10 is wound while the winding position of the composite fiber bundle 10 around the mandrel 34 is shifted in the axial direction of the mandrel 34.

[0070] First, the winding angle, which is the angle of the composite fiber bundle 10 relative to the axial direction of the mandrel 34, is set to θ1 (= inclination angle θ1), and the resin application device 32 is reciprocated at a moving speed corresponding to this winding angle θ1, thereby helically winding the composite fiber bundle 10 to which the matrix resin M has been applied around the mandrel 34.

[0071] Here, when the winding angle is assigned a positive or negative sign to distinguish the direction of the angle relative to the mandrel 34, as with the inclination angle, the composite fiber bundle 10 is wound around the mandrel 34 at a winding angle of +θ1 when the resin applicator 32 moves forward, and at a winding angle of -θ1 when it moves backward. By repeating the reciprocating motion multiple times, a helical unit layer is formed in which the composite fiber bundle 10 is wound around the mandrel 34 without gaps in the axial direction of the mandrel 34 at a winding angle of +θ1 and also at a winding angle of -θ1. The resin applicator 32 is reciprocated a number of times according to the thickness D1 of the helical layer 6 (the number of helical unit layers) to complete the helical winding.

[0072] Following the helical winding, hoop winding is performed. The winding angle is set to θ2 (= inclination angle θ2), and the resin applicator 32 is reciprocated at a moving speed corresponding to this winding angle θ2. One forward motion of the resin applicator 32 forms a hoop unit layer in which the composite fiber bundle 10 is densely wound adjacent to each other without overlapping in the axial direction of the mandrel 34 at a winding angle +θ2. The subsequent return motion forms a hoop unit layer in which the composite fiber bundle 10 is densely wound adjacent to each other without overlapping in the axial direction of the mandrel 34 at a winding angle −θ2, overlapping the outer periphery of the hoop unit layer formed in the previous forward motion. In this manner, the resin applicator 32 is reciprocated a number of times corresponding to the thickness D2 of the hoop layer 7 (the number of hoop unit layers) to complete the hoop winding.

[0073] As described above, during helical winding and hoop winding, the composite fiber bundle 10 is wound around the mandrel 34 with a predetermined tension applied to the composite fiber bundle 10. It is particularly preferable to prevent misalignment of the winding position, which can cause loose winding or uneven winding of the composite fiber bundle 10, at both ends of the molding region when the composite fiber bundle 10 is turned from the forward motion to the backward motion and from the backward motion to the forward motion, during helical winding. For this purpose, it is preferable to attach pin rings, for example, each having a plurality of pins radially arranged at a predetermined pitch, to both ends of the molding region of the mounting mandrel, and wind the composite fiber bundle 10 while passing it between the pins. It is also preferable to wind the composite fiber bundle 10 for several turns near both ends of the molding region of the mandrel 34 to prevent misalignment. When winding to prevent misalignment, it is also preferable to use a composite fiber bundle, such as a 1K or 3K fiber bundle, in which the number of composite fibers 11 is reduced by splitting the 12K composite fiber bundle 10, in order to reduce the step between the wound portion for preventing misalignment and the wound portion in the molding region.

[0074] In this example, the composite fiber bundle 10 is wound around the mandrel 34 without being spread, but the composite fiber bundle 10 may be spread by, for example, a spreading roller and then wound around the mandrel 34. Furthermore, during each of the forward and backward movements, a part of the spread composite fiber bundle 10 may be wound so as to overlap the part of the composite fiber bundle 10 that was wound during the previous forward or backward movement.

[0075] After forming a molded body by winding the composite fiber bundle 10 around the outer peripheral surface of the mandrel 34 as described above, the mandrel 34 is removed from the filament winder 33 together with the molded body. The molded body is heated, for example, together with the removed mandrel 34, to harden the matrix resin M applied to the composite fiber bundle 10. The molded body with the hardened matrix resin M is removed from the mandrel 34 and cut to a desired width to form the rotating member 2.

[0076] As the resin applicator 32, for example, a touch roll type is used as shown in Fig. 13. In this resin applicator 32, the lower part of a touch roll 35 is immersed in uncured liquid matrix resin M stored in a storage tank 36, and the composite fiber bundle 10 is pressed against the upper outer peripheral surface of the touch roll 35 by a pair of guide rollers 35a. As the touch roll 35 rotates, the stored liquid matrix resin M is applied to the composite fiber bundle 10 via the outer peripheral surface of the touch roll 35. By adjusting the rotation speed of the touch roll 35, the pressing force of the pair of guide rollers 35a on the composite fiber bundle 10 against the touch roll 35, etc., the amount of matrix resin M applied to the composite fiber bundle 10, i.e., the carbon fibers 12 forming the structure 14, can be adjusted, and the structure 14 can be sufficiently impregnated with the matrix resin M applied.

[0077] For example, the tension of the composite fiber bundle 10 when it is wound around the mandrel 34 is adjusted by increasing or decreasing the rotational load of the guide roller 35a downstream of the touch roll 35, and the guide roller 35a serves as a tension adjustment mechanism. Note that the method for adjusting the tension of the composite fiber bundle 10 is not limited to this, and for example, a separate mechanism for adjusting the tension may be provided.

[0078] It has been confirmed that there is a positive correlation between the tensile strength of the rotating member 2 and the fiber volume content (Vf) of the carbon fibers 12. From the viewpoint of increasing tensile strength, a higher fiber volume content of the carbon fibers 12 is preferable. The fiber volume content of the carbon fibers 12 may be, for example, 75% or more or less than 75%. On the other hand, as the fiber volume content increases, the amount of matrix resin M serving as a binder in the rotating member 2 decreases, and the brittleness resistance of the rotating member 2 tends to decrease. For this reason, from the viewpoint of the brittleness resistance of the rotating member 2, it is preferable to set the fiber volume content to less than 75%. Furthermore, from the viewpoint of ensuring sufficient tensile strength, the fiber volume content of the carbon fibers 12 is preferably 65% or more, more preferably 67% or more. For these reasons, a fiber volume content of the rotating member 2 of 65% or more but less than 75% is a preferred embodiment, and a fiber volume content of 67% or more but less than 75% is a more preferred embodiment. The fiber volume content of the carbon fibers 12 in the rotating member 2 can be changed, for example, by adjusting the amount of matrix resin M applied to the composite fiber bundle 10 by the resin application device 32 or the tension of the composite fiber bundle 10 when wound around the mandrel 34.

[0079] The fiber volume content of the carbon fibers 12 of the rotating member 2 can be calculated using, for example, formula (1). The value ρ in formula (1) is the specific gravity of the rotating member 2, and the value ρ f is the specific gravity of carbon fiber 12, value ρ m is the specific gravity of the matrix resin M. The specific gravity ρ of the rotating member 2 and the specific gravity ρ of the matrix resin M m The specific gravity ρ of the carbon fiber 12 is a value measured by a measuring instrument (for example, a high-precision electronic specific gravity meter SD-200L (manufactured by Alpha Mirage Co., Ltd.)). f For the specific gravity ρ, a value measured by a measuring instrument similar to that of the rotating member 2, etc., or a catalog value (nominal value of the manufacturer of the carbon fiber 12) may be used. Note that the specific gravity of the CNTs 17 and the sizing agent 15 attached to the carbon fiber 12 is very small compared to the specific gravity of the carbon fiber 12, so the specific gravity of the carbon fiber 12 alone is used as the specific gravity ρ f It may be considered as such.

[0080]

number

[0081] In the molding step ST3, when curing the matrix resin M, which is a thermosetting resin of the molded body produced by winding the composite fiber bundle 10 around the mandrel 34, the heating temperature is preferably changed in stages to improve the accuracy of the inner diameter dimension of the rotating member 2. In the example shown in Fig. 14, the temperature is changed in two stages in the curing step for curing the matrix resin M of the molded body, where the temperature is raised from room temperature to a first heating temperature T1 and maintained at the first heating temperature T1 for a predetermined time, and then raised to a second heating temperature T2 higher than the first heating temperature T1 and maintained at the second heating temperature T2 for a predetermined time. After maintaining the second heating temperature T2 for the predetermined time, the molded body is allowed to cool naturally, and then it is removed from the mandrel 34 to form the rotating member 2.

[0082] The first heating step, in which the molded body is heated at the first heating temperature T1, is a step of promoting gelation and hardening of the matrix resin M with the primary objective of hardening the molded body to a stable shape with little size variation while suppressing thermal expansion or thermal contraction of the mandrel 34 due to heating, in order to reduce the error in the inner diameter dimension of the manufactured rotating member 2. For this reason, the first heating temperature T1 is set to a temperature that minimizes thermal expansion of the mandrel 34. Furthermore, heating at the first heating temperature T1 is continued until the molded body obtains a stable shape, that is, until it can be said to have hardened, even if it does not obtain its final strength.

[0083] More specifically, the time for maintaining the first heating temperature T1 is determined, for example, as the time until the storage modulus of the matrix resin M becomes substantially constant. Suppressing the thermal expansion or thermal contraction of the molded body in the first heating step is preferable in order to further reduce the error in the inner diameter dimension of the rotating member 2. In this case, the first heating temperature T1 is set to a temperature that minimizes the thermal expansion or thermal contraction of the mandrel 34 and is below the glass transition point of the matrix resin M at the end of the first heating step (a constant temperature below the glass transition point of the matrix resin M that increases during the first heating step) in order to suppress the thermal expansion or thermal contraction of the molded body. This is also done in this example.

[0084] The time for which the matrix resin M is maintained at the first heating temperature T1 may be the time until the rate of change (rate of increase) in the storage modulus of the matrix resin M starts to decrease, or until the loss modulus reaches or peaks out. For example, a rheometer can be used to determine the changes in the storage modulus and loss modulus of the matrix resin M with respect to heating time at each heating temperature, and the time for which the matrix resin M is maintained at the first heating temperature T1 can be determined in advance. The glass transition point of the matrix resin M can also be determined in advance.

[0085] In the second heating step, the molded body is heated at a second heating temperature T2, which is higher than the first heating temperature T1, to promote curing of the matrix resin M that has been subjected to the first heating step, thereby achieving the final strength, elastic modulus, and heat resistance of the rotating member 2. The second heating temperature T2 in the second heating step is preferably a temperature exceeding the glass transition point of the matrix resin M. When the matrix resin M is a cyanate ester resin, for example, the first heating temperature T1 is preferably within a range of 100°C or higher and 200°C or lower, and the second heating temperature T2 is preferably within a range of 200°C or higher and 300°C or lower.

[0086] By changing the heating temperature stepwise as described above, the molded body is heated at the first heating temperature T1 in the first heating step, whereby the matrix resin M is cured and a stable shape is formed for the molded body. Subsequently, in the second heating step, the matrix resin M of the molded body is further cured, and the molded body is given its final strength, elastic modulus, and heat resistance. The inner diameter of the rotating member 2 produced in this manner is substantially determined when the stable shape of the molded body is formed in the first heating step. Because the first heating step involves heating at the first heating temperature T1, the thermal expansion of the mandrel 34 and the thermal expansion or contraction of the matrix resin M are small. This allows for a molded body, i.e., a rotating member 2, with a small error in the inner diameter dimension to be obtained.

[0087] In the second heating step, the compact is heated to the second heating temperature T2, which causes the mandrel 34 to thermally expand more than in the first heating step, and the compact, which has stabilized, is deformed by this thermal expansion. However, since most of this deformation is elastic, it returns to its original shape after cooling. Therefore, the effect of the inner diameter of the compact on the second heating step is very small.

[0088] When the heating temperature was changed stepwise as described above and the mandrel 34 was actually manufactured using carbon steel for machine structural use S45C, the inner diameter dimension of 50 samples A of the rotating member 2 was 40 mm ± 0.003 mm. In contrast, the inner diameter dimension of 50 samples B of the rotating member 2 manufactured by raising the temperature from room temperature to the second heating temperature T2 together with the mandrel 34 made from the same material and hardening it was 40 mm ± 0.01 mm or more.

[0089] In the case of Sample A, the temperature was raised from room temperature and maintained at the first heating temperature T1 for 90 minutes, and then raised from the first heating temperature T1 to the second heating temperature T2 for 120 minutes. In the case of Sample B, the temperature was raised from room temperature to the second heating temperature T2 and maintained at the second heating temperature T2 for 210 minutes. The first heating temperature T1 for Sample A was 145°C, and the second heating temperature T2 for Samples A and B was 200°C.

[0090] By gradually changing the heating temperature as described above to harden the matrix resin M of the molded body, it becomes easier to control the inner diameter dimension of the rotating member 2 to be produced, and it is found that a rotating member 2 can be produced with reduced error relative to the desired inner diameter dimension.

[0091] The heating temperature in the first heating step may be changed in two or more stages, and heating may be performed for a predetermined time at each heating temperature. Even when the heating temperature in the first heating step is changed in two or more stages in this way, it is preferable that the second heating temperature T2 in the second heating step, i.e., the final heating temperature, exceeds the glass transition point of the matrix resin M.

[0092] As shown schematically in FIG. 15 , the rotating member 2 using the composite fiber bundle 10 has a cross-linked structure in which the carbon fibers 12 are cross-linked by cross-linking portions CL formed by portions of the composite regions 19 between the carbon fibers 12 being fixed to each other. As described above, the composite regions 19 are regions made up of the structure 14 and the matrix resin M that has been impregnated into the structure 14 and cured. The composite regions 19 are harder than the cured matrix resin alone and have high elasticity, i.e., a large elastic limit. The composite regions 19 also have higher abrasion resistance than the matrix resin M. The bonding between the composite regions 19 in this manner strengthens the bonding between the carbon fibers 12, improving the tensile strength of the rotating member 2 using the composite fiber bundle 10.

[0093] A crosslinked structure is formed when the carbon fibers 12 are close enough to contact each other, so a thicker structure 14 is more advantageous in terms of increasing the number of crosslinks. However, from the viewpoints of ensuring quality stability through a uniform thickness and preventing the carbon fibers 12 from falling off, it is preferable that the thickness of the structure 14 be at most 300 nm or less. In particular, it is preferable that the thickness of the structure 14 be in the range of 50 nm or more and 200 nm or less.

[0094] Furthermore, because the structure 14 is made up of a plurality of CNTs 17 entangled with each other in a thick nonwoven fabric, the matrix resin M applied to the carbon fibers 12 is retained in an impregnated state within the structure 14. Therefore, in a carbon fiber reinforced molded product such as the rotating member 2, regardless of the molding method, there is almost no bias in the matrix resin M on the surface of the carbon fibers 12, and the spacing between the carbon fibers is uniform. For this reason, load is transmitted uniformly between the carbon fibers via the shear force of the matrix resin M, and the tensile strength of the rotating member 2 is effectively increased.

[0095] Figure 16 shows an SEM image of the cross section of a rotating member 2 made using a composite fiber bundle 10. Figure 17 shows an SEM image of the cross section of a rotating member made in the same manner using a carbon fiber bundle made of carbon fibers (raw yarn) without CNTs attached. In both cross sections, close-packed areas where the carbon fibers were packed very densely were observed, confirming that the amount of matrix resin absorbing deformation of the rotating member was small.

[0096] In rotating components made with carbon fibers (raw yarns) without CNTs attached, a clear boundary line is observed at the interface between the carbon fibers and the matrix resin. Furthermore, in the closest-packed areas, adjacent carbon fibers are in contact with each other, or only a very thin layer of matrix resin is present between adjacent carbon fibers. Therefore, the bond strength between two adjacent carbon fibers does not exceed the adhesive strength at the interface between the carbon fiber and the matrix resin. Furthermore, as the fiber volume fraction (Vf) increases, the amount of matrix resin decreases, and the rotating component tends to become more brittle.

[0097] In contrast, in the rotating member 2 using the composite fiber bundle 10, it can be seen that a composite region 19 in which the structure 14 is impregnated with the matrix resin M and hardened is formed around the carbon fiber 12. It can be seen that such a composite region 19 increases the interfacial adhesive strength between the carbon fiber 12 and the matrix resin M, thereby increasing the tensile strength of the rotating member 2. It can also be seen that the above-mentioned cross-linked structure is formed in the closest-packed areas, which strengthens the interaction between the carbon fibers and improves the tensile strength.

[0098] Although the above describes an example of a rotating member used in a surface permanent magnet motor, the rotating member may be fitted onto the rotor of other types of electric motors and generators. Furthermore, in electric motors and generators, other members may be integrally formed or attached to the inner or outer periphery of a cylindrical, ring-shaped, or other rotating member. Therefore, in electric motors and generators, the carbon fiber reinforced layer that becomes the rotating member may be formed as part of a member that includes other members. [Example]

[0099] Example 1 In Example 1, a composite fiber bundle 10 was produced using the above procedure, and a peeling experiment of CNTs 17 was performed to confirm the effect of the sizing agent 15. The dispersion 28 used in producing the composite fiber bundle 10 was prepared using material CNTs with a curved shape as described above. Figure 18 shows an SEM image of the material CNTs used in preparing the dispersion 28. The material CNTs were multilayered and had diameters ranging from 3 nm to 10 nm. The material CNTs were washed with a 3:1 mixed acid of sulfuric acid and nitric acid to remove catalyst residue, and then filtered and dried. The material CNTs were added to acetone, which served as the dispersion medium for the dispersion 28, and the material CNTs were cut using an ultrasonic homogenizer to obtain CNTs 17. The length of the CNTs 17 in the dispersion 28 was 0.2 μm to 5 μm. The CNTs 17 in the dispersion 28 were also evaluated as having a curved shape. The concentration of CNT 17 in the dispersion 28 was set to 0.12 wt % (=1200 wt ppm). No dispersant or adhesive was added to the dispersion 28.

[0100] Torayca (registered trademark) T1100SC (manufactured by Toray Industries, Inc.) was used as the carbon fiber bundle 18 used to produce the composite fiber bundle 10. This carbon fiber bundle 18 contains 12,000 carbon fibers 12. The carbon fibers 12 have a diameter of about 7 μm and a length of about 500 m. Prior to attaching the CNTs 17 to the carbon fiber bundle 18, the sizing agent used to prevent entanglement of the carbon fibers 12 was removed from the surface of the carbon fibers 12.

[0101] The carbon fiber bundle 18 was wound around guide rollers 23 to 26 in an open state and allowed to travel through the dispersion liquid 28 in the CNT adhesion tank 22. The traveling speed of the carbon fiber bundle 18 was 1 m / min, and ultrasonic vibrations with a frequency of 200 kHz were applied to the dispersion liquid 28 by an ultrasonic generator 27. The immersion time during which the carbon fiber bundle 18 traveled between the guide rollers 24 and 25 was 6.25 seconds. This immersion time corresponded to 1,250,000 cycles of the ultrasonic vibrations applied to the dispersion liquid 28.

[0102] The carbon fiber bundles 18 drawn out from the dispersion liquid 28 were dried, and then a sizing treatment was carried out to apply the sizing agent 15 to the CNTs 17 constituting the structure 14. In the sizing treatment, a sizing treatment solution prepared by dissolving "Carbodilite V-02" (trade name, manufactured by Nisshinbo Chemical Inc.) in water as a carbodiimide compound was used. The concentration of the carbodiimide compound in the sizing treatment solution was adjusted so as not to clog the voids 20 in the structure 14. The carbon fiber bundles 18 that had been subjected to the sizing treatment were dried to obtain a composite fiber bundle 10.

[0103] A plurality of composite fibers 11 obtained by cutting out a portion of the composite fiber bundle 10 that had been subjected to the sizing treatment as described above were observed using an SEM to confirm that a plurality of CNTs 17 were uniformly dispersed and attached to the carbon fibers 12. As a result, it was confirmed that the CNTs 17 were attached uniformly both in a narrow range (local) and a wide range in the fiber axis direction of the carbon fibers 12, forming a structure 14. It was also confirmed that the structure 14 was formed in the form of a nonwoven fabric having a three-dimensional mesh structure, i.e., voids 20, made up of a large number of CNTs 17, and that most of the voids 20 were not blocked by the sizing agent 15.

[0104] Using the composite fiber bundle 10 produced as described above as the reinforcing fiber, a plurality of ring-shaped test pieces A1 were produced as rotating members 2 having different fiber volume contents (Vf) of the carbon fibers 12, and the tensile strength of each was measured by the NOL ring test (based on ASTM D2290). Furthermore, as Comparative Example 1, a plurality of ring-shaped test pieces B1 were produced using raw yarn (carbon fiber) as the reinforcing fiber and having different fiber volume contents (Vf) of the carbon fibers, and the tensile strength of each was measured in the same manner. The carbon fiber bundle used in Comparative Example 1 was the same as that in Example 1.

[0105] For the ring-shaped test pieces A1 and B1, the inclination angle θ1 of the helical layer was 40°, and the inclination angle θ2 of the hoop layer was approximately 90° (substantially perpendicular). Furthermore, the thickness of each of the ring-shaped test pieces A1 and B1 was 1.83 mm, and the ratio of the helical winding thickness D1 to the hoop winding thickness D2 was 5.1 (= D2 / D1). That is, the helical layer thickness D1 was 0.3 mm, and the hoop layer thickness D2 was 1.53 mm. The NOL ring tests for Example 1 and Comparative Example 1 were both performed using a Model 5582 universal testing machine (manufactured by Instron) at a tensile speed of 2 mm / min.

[0106] The measurement results are shown in Figure 19. In Figure 19, ● represents the plot of each measurement result for Example 1 (ring-shaped test piece A1), and ○ represents the plot of each measurement result for Comparative Example 1 (ring-shaped test piece B1). The horizontal axis of Figure 19 represents the fiber volume content (Vf) of the carbon fiber in the ring-shaped test piece, and the vertical axis represents the breaking strength (= tensile strength) per mm of width of the ring-shaped test piece. The solid line is an approximate straight line showing the relationship between the fiber volume content and the breaking strength based on each measurement value for Example 1, and the dashed line is an approximate straight line showing the relationship between the fiber volume content and the breaking strength based on each measurement value for Comparative Example 1. Figure 20 shows an enlarged view of the region of Figure 19 where the fiber volume content is 60% or more and 80% or less.

[0107] 19 and 20, it was confirmed that the tensile strength improved in direct proportion to the fiber volume content. It was also found that the ring-shaped test piece A1 had a higher tensile strength at a lower fiber volume content than the ring-shaped test piece B1. In other words, it was found that the rotating member 2 using the composite fiber 11 as the reinforcing fiber had a higher tensile strength than a rotating member using carbon fiber yarn with the same fiber volume content.

[0108] The results of Example 1 show that a rotating member 2 using composite fiber 11 as the reinforcing fiber has a higher tensile strength than one using raw yarn as the reinforcing fiber, and that a rotating member 2 that combines high tensile strength and high brittle resistance can be obtained. Also, it is clear that the tensile strength of a rotating member 2 made using composite fiber 11 as the reinforcing fiber can be made to be the same as or higher than that of a rotating member using raw yarn as the reinforcing fiber and a fiber volume content of 75%, so that sufficient tensile strength can be obtained. [Explanation of symbols]

[0109] 2 Rotating members 3 Surface magnet type electric motor 4 rotors 10. Composite fiber bundle 11 Composite Fiber 12 Carbon Fiber 14 Structure 15 Sizing agent 17 Carbon nanotubes M matrix resin

Claims

1. A rotating member that is a carbon fiber reinforced molded body in which carbon fibers are embedded in a matrix resin and that rotates integrally with the rotating body of an electric motor or generator, a helical layer in which composite carbon fibers are oriented at an inclination angle of 40° to 80° with respect to the axial direction of the rotating member; a hoop layer in which the composite carbon fibers are oriented in a direction substantially perpendicular to the axial direction of the rotating member; Equipped with The composite carbon fiber is a structure provided on the surface of the carbon fiber, the structure being composed of a plurality of bent carbon nanotubes having bent portions, and forming a network structure having contact portions where the carbon nanotubes are in direct contact with each other; a sizing agent that crosslinks the carbon nanotubes that are in direct contact with each other; A rotating member comprising:

2. 2. The rotating member according to claim 1, wherein the value D2 / D1 is in the range of 5 to 20, where D1 is the thickness of the helical layer and D2 is the thickness of the hoop layer.

3. 3. The rotating member according to claim 1, wherein the fiber volume content of the carbon fibers is 65% or more and less than 75%.

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