Cylindrical member and method for manufacturing a cylindrical member

Abstract

This improves the allowable tensile stress of the cylindrical member covering the outer surface of the rotor. [Solution] The cylindrical member 10 includes a first layer 20 and a second layer 30 in that order, from the inner circumferential surface 11 toward the outer circumferential surface 12. The first layer 20 includes a plurality of first carbon fibers 25. The orientation angle of the plurality of first carbon fibers 25 with respect to the axial direction DA is 85° or more and 90° or less. The second layer 30 includes a plurality of second carbon fibers 35. The orientation angle of the plurality of second carbon fibers 35 with respect to the axial direction DA is 45° or more and less than 85°.

Description

【Technical Field】 【0001】 The present invention relates to a cylindrical member and a method for manufacturing the cylindrical member. 【Background Art】 【0002】 For example, as disclosed in Patent Document 1, a cylindrical member that covers a rotor of a motor from a direction orthogonal to the rotation axis of the rotor is known. The rotor includes magnets. The rotor and the cylindrical member constitute a cover rotor. The cover rotor is rotatably disposed within a stator. The cylindrical member suppresses the dropout of magnets in the rotating rotor with respect to the stator. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Translation of PCT International Publication No. 2023-527675 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 When the cover rotor rotates, a centrifugal force acts on the cylindrical member as an inertial force. The cylindrical member receives a tensile stress in the circumferential direction due to the centrifugal force. If the cylindrical member exceeds the allowable value of the tensile stress in the circumferential direction, it breaks. Due to the breakage of the cylindrical member, in the cover motor, the function of suppressing the dropout of magnets during rotation is at least partially lost. An object of the present invention is to improve the durability against tensile stress in the circumferential direction in a cylindrical member that covers the outer peripheral surface of a rotor. 【Means for Solving the Problems】 【0005】 A cylindrical member according to an embodiment of the present invention is a cylindrical member that covers a rotor of a motor from a direction orthogonal to the rotation axis of the rotor, comprising a first layer and a second layer in this order from the inner peripheral surface toward the outer peripheral surface, The first layer contains first carbon fibers having an orientation angle of 85° or more and 90° or less with respect to the axial direction parallel to the axis of the cylindrical member. The second layer contains second carbon fibers having an orientation angle of 45° or more and less than 85° with respect to the axial direction. 【0006】 A method for manufacturing a first cylindrical member according to one embodiment of the present invention is: A method for manufacturing a cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, A first winding step involves winding a first prepreg sheet containing multiple carbon fibers oriented in a first direction around the outer surface of a core material, A second winding step involves winding a second prepreg sheet containing a plurality of carbon fibers oriented in a second direction onto the core material so as to overlap the first prepreg sheet, The process includes a curing step for curing the first prepreg sheet and the second prepreg sheet, The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. The angle between the second direction and the axis direction is 45° or more and less than 85°. 【0007】 A method for manufacturing a second cylindrical member according to one embodiment of the present invention is: A method for manufacturing a cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, A bonding process for joining a first prepreg sheet containing a plurality of carbon fibers oriented in a first direction and a second prepreg sheet containing a plurality of carbon fibers oriented in a second direction, A winding step in which the first prepreg sheet and the second prepreg sheet are wound around the outer surface of the core material, The process includes a curing step for curing the first prepreg sheet and the second prepreg sheet, The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. The angle between the second direction and the axis direction is 45° or more and less than 85°. [Effects of the Invention] 【0008】 According to the present invention, in a cylindrical member that covers the outer peripheral surface of a rotor, the durability against tensile stress in the circumferential direction can be improved. 【Brief Description of the Drawings】 【0009】 [Figure 1] FIG. 1 is a diagram for explaining an embodiment, and is an exploded perspective view of a motor. [Figure 2] FIG. 2 is a view of a cover rotor included in the motor of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view of a cylindrical member included in the cover rotor of FIG. 2. [Figure 4] FIG. 4 is an enlarged view when the first layer of the cylindrical member of FIG. 3 is observed from the radial direction. [Figure 5] FIG. 5 is an enlarged view when the inner second layer of the cylindrical member of FIG. 3 is observed from the radial direction. [Figure 6] FIG. 6 is an enlarged view when the outer second layer of the cylindrical member of FIG. 3 is observed from the radial direction. [Figure 7] FIG. 7 is a diagram for explaining an example of a manufacturing method of the cylindrical member of FIG. 3. [Figure 8] FIG. 8 is a diagram for explaining a method for evaluating the durability of the cylindrical member against tensile stress in the circumferential direction. [Figure 9] FIG. 9 is a cross-sectional view of a modified example of the cylindrical member. 【Embodiments for Carrying Out the Invention】 [[ID=##]] [[ID=##]] 【0010】 [[ID=##]] One embodiment of the present invention relates to the following [1] to [8]. 【0011】 [1] A cylindrical member that covers the rotor of a motor from a direction orthogonal to the rotation axis of the rotor, [[ID=##]] comprising a first layer and a second layer in this order from the inner peripheral surface toward the outer peripheral surface, The first layer includes a plurality of first carbon fibers having an orientation angle of 85° or more and 90° or less with respect to the axial direction parallel to the axis of the cylindrical member. The second layer is a cylindrical member including a plurality of second carbon fibers having an orientation angle of 45° or more and less than 85° with respect to the axial direction. 【0012】 [2] The cylindrical member according to [1], wherein the thickness of the first layer in the radial direction orthogonal to the axis is larger than the thickness of the second layer in the radial direction. 【0013】 [3] The cylindrical member according to [1] or [2], wherein the maximum strain in the radial direction orthogonal to the axis is 0.10 or more and 0.25 or less. 【0014】 [4] The second layer includes an inner second layer and an outer second layer that overlap in the radial direction orthogonal to the axis. The inner second layer includes a plurality of inner second carbon fibers oriented so as to have an inner second orientation direction when observed from the radial direction. [1] to [3] The cylindrical member, wherein the outer second layer includes a plurality of outer second carbon fibers oriented so as to have an outer second orientation direction symmetric with respect to the inner second orientation direction and the axis when observed from the radial direction. 【0015】 [5] A method for manufacturing a cylindrical member that covers a rotor of a motor from a direction orthogonal to the rotation axis of the rotor, a first winding step of winding a first prepreg sheet including a plurality of carbon fibers oriented in a first direction around an outer peripheral surface of a core material; a second winding step of winding a second prepreg sheet including a plurality of carbon fibers oriented in a second direction around the core material so as to overlap the first prepreg sheet; and a curing step of curing the first prepreg sheet and the second prepreg sheet. The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. The method for manufacturing a cylindrical member, wherein the angle between the second direction and the core axis direction is 45° or more and less than 85°. 【0016】 [6] A third winding step performed between the second winding step and the curing step, further comprising winding a third prepreg sheet containing a plurality of carbon fibers oriented in a third direction onto the core material so as to overlap the second prepreg sheet, In the curing step, the first prepreg sheet, the second prepreg sheet, and the third prepreg sheet are cured. The method for manufacturing a cylindrical member [5], wherein the third direction is symmetric with respect to the second direction and the axis direction. 【0017】 [7] A bonding step performed prior to the second winding step, further comprising bonding a third prepreg sheet containing a plurality of carbon fibers oriented in a third direction to the second prepreg sheet, The third direction is symmetrical with respect to the second direction and the axis direction, A method for manufacturing a cylindrical member according to [5] or [6], wherein in the second winding step, the second prepreg sheet and the third prepreg sheet are wound around the core material. 【0018】 [8] A method for manufacturing a cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, A bonding process for joining a first prepreg sheet containing a plurality of carbon fibers oriented in a first direction and a second prepreg sheet containing a plurality of carbon fibers oriented in a second direction, A winding step in which the first prepreg sheet and the second prepreg sheet are wound around the outer surface of the core material, The process includes a curing step for curing the first prepreg sheet and the second prepreg sheet, The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. A method for manufacturing a cylindrical member, wherein the angle between the second direction and the core axis direction is 45° or more and less than 85°. 【0019】 An embodiment of the present invention will be described with reference to the drawings. For ease of illustration and understanding, the dimensional ratios in the drawings may be changed from the dimensional ratios of the actual object. Components shown in one drawing may be omitted in other drawings. 【0020】 The terms used to specify shapes, geometric conditions such as "parallel" and "orthogonal," and values ​​of lengths and angles are not interpreted strictly, but rather within a range that allows for the expectation of similar functionality. 【0021】 Directions common to multiple drawings are indicated by arrows with a common reference numeral in each drawing. In each illustrated direction, the tip of the arrow is the first side, and the opposite side, i.e., the base of the arrow, is the second side. The first side in a direction perpendicular to the drawing is indicated by a symbol of a circle with a dot inside. The second side in a direction perpendicular to the drawing is indicated by a symbol of a circle with an X inside. 【0022】 Figures 1 to 6 illustrate one embodiment. Figure 1 is an exploded perspective view of motor 1. Motor 1 in Figure 1 includes a stator 2 and a cover rotor 3. The cover rotor 3 is held so as to be rotatable about the rotation axis AR relative to the stator 2. Motor 1 outputs rotational motion of the cover rotor 3 relative to the stator 2. The cover rotor 3 includes a rotor 4 and a cylindrical member 10 that covers the rotor 4 from a direction perpendicular to the rotation axis AR. The cylindrical member 10 rotates together with the rotor 4 about the rotation axis AR relative to the stator 2. 【0023】 The rotor 4 in Figures 1 and 2 includes a rotor body 5 and a plurality of magnets 6 attached to the rotor body 5. The magnets 6 in Figures 1 and 2 are joined to the outer circumferential surface of the rotor body 5. Unlike in Figures 1 and 2, the magnets 6 may be embedded in the rotor body 5. In a rotor 4 in which the magnets 6 are embedded in the rotor body 5, the magnets 6 do not have to constitute the outer circumferential surface of the rotor 4. 【0024】 The rotor 4 generates a magnetic field using magnets 6. The rotor 4 and the cover rotor 3, which includes the rotor 4, rotate relative to the stator 2 due to the magnetic field generated by the magnets 6. The rotor 4 shown in Figures 1 and 2 includes four magnets 6 arranged in the direction of rotation around the rotation axis AR. The multiple magnets 6 constitute the outer circumferential surface of the rotor 4. The magnets 6 may be permanent magnets. 【0025】 The stator 2 in Figure 1 has a cylindrical shape. The stator 2 is open at both ends in a direction parallel to the rotation axis AR. The stator 2 has an inner circumferential surface 7 and an outer circumferential surface 8. In the motor 1 of Figure 1, when the cover rotor 3 is housed in the stator 2, the inner circumferential surface 7 of the stator and the outer circumferential surface of the cover rotor 3 move away from each other in a direction perpendicular to the rotation axis AR. 【0026】 The inner circumferential surface 7 of the stator may be composed of electromagnets. The cover rotor 3 may rotate around the rotation axis AR relative to the stator 2 when the electromagnets constituting the inner circumferential surface 7 are energized, i.e., when they function as magnets. The cover rotor 3 may stop rotating relative to the stator 2 when the electromagnets constituting the inner circumferential surface 7 are not energized, i.e., when they are not functioning as magnets. 【0027】 Incidentally, in a rotor that rotates relative to a stator, a centrifugal force acts as an inertial force on the magnets that rotate with the rotor body. The centrifugal force acts outward in a direction perpendicular to the rotor's axis of rotation, that is, away from the axis of rotation. As the rotor's rotational speed increases, the centrifugal force acting on the magnets also increases. As a result, at high-speed rotation of the rotor, the magnets attached to the rotor body may detach from the rotor body. 【0028】 In contrast, the rotor 4 in Figures 1 and 2 is covered from the outside in a direction perpendicular to the rotation axis AR by a cylindrical member 10. The rotor 4 and the cylindrical member 10 constitute the cover rotor 3. In the cover rotor 3, the movement of the rotor 4 and the cylindrical member 10 relative to each other is suppressed. The cylindrical member 10 presses the magnet 6 attached to the rotor body 5 toward the rotor body 5. As a result, the cylindrical member 10 suppresses the aforementioned detachment of the magnet 6 from the rotor body 5, even when the cover rotor 3 is rotating at high speed. 【0029】 As shown in Figures 1 and 3, the cylindrical member 10 has a cylindrical shape with an inner circumferential surface 11 and an outer circumferential surface 12. As shown in Figure 3, the cylindrical member 10 extends in the circumferential direction DC centered on the axis AS and in the axial direction DA parallel to the axis AS. The inner circumferential surface 11 and the outer circumferential surface 12 are separated from each other in the radial direction DR perpendicular to the axis AS. Figure 3 shows a cross-sectional view of the cylindrical member 10 with respect to a plane perpendicular to the axial direction DA. 【0030】 The cylindrical member 10 may be attached to the rotor 4 by shrink fitting. In shrink fitting, first, the rotor 4 is contracted so that its outer diameter is smaller than the inner diameter of the cylindrical member 10. The rotor 4 contracts due to cooling. The "outer diameter of the rotor 4" is the dimension in the direction perpendicular to the rotation axis AR of the rotor 4. The "inner diameter of the cylindrical member 10" is the maximum value of the dimension in the radial direction DR of the inner circumferential surface 11. After positioning the rotor 4, which has contracted due to cooling, inside the inner circumferential surface 11, the temperature of the rotor 4 is increased. The rotor 4 returns to its pre-contraction state due to the increase in temperature, and as a result, the cylindrical member 10 is attached to the rotor 4, forming the cover rotor 3. In the cover rotor 3, the movement of the rotor 4 and the cylindrical member 10 relative to each other is restricted. 【0031】 The cylindrical member 10 may be attached to the rotor 4 by a method other than the cold-fit method described above. For example, the cylindrical member 10 may be attached to the rotor 4 by an adhesive, tack, or the like. The cover rotor 3 may include a bonding layer between the rotor 4 and the cylindrical member 10. The bonding layer may be made of an adhesive, tack, or the like. 【0032】 As shown in Figure 3, the cylindrical member 10 includes a first layer 20 and a second layer 30 in that order, extending from the inner circumferential surface 11 to the outer circumferential surface 12. The first layer 20 and the second layer 30 are stacked in the radial direction DR. Each of the first layer 20 and the second layer 30 shown in Figure 3 extends in the circumferential direction DC and the axial direction DA. The inner circumferential surface 11 of the illustrated cylindrical member 10 is composed of the first layer 20. The outer circumferential surface 12 of the illustrated cylindrical member 10 is composed of the second layer 30. 【0033】 Each of the first layer 20 and the second layer 30 may contain a cured resin product. The cured resin product is a cured product of a curable resin composition. The cured resin product contained in the first layer 20 and the cured resin product contained in the second layer 30 may be formed by curing a curable resin composition contained in the prepreg sheet 50, which will be described later. 【0034】 In the cylindrical member 10 shown in Figure 3, the thickness of the first layer 20 in the radial direction DR is greater than the thickness of the second layer 30 in the radial direction DR. In the radial direction DR, the thickness of the first layer 20 may be 5 to 10 times the thickness of the second layer 30. 【0035】 The thickness of the first layer 20 and the thickness of the second layer 30 in the radial DR are obtained by observing the cross-section of the cylindrical member 10 as illustrated in Figure 3. An optical microscope (KEYENCE Digital Microscope VHX-950F) is used to observe the cross-section of the cylindrical member 10. 【0036】 The first layer 20 contains a plurality of first carbon fibers 25. Figure 4 is an enlarged view of the first layer 20 as observed from the radial direction DR. Each of the plurality of first carbon fibers 25 is linear, as shown in Figure 4. The second layer 30 contains a plurality of second carbon fibers 35. Figures 5 and 6 are enlarged views of the second layer 30 as observed from the radial direction DR. Each of the plurality of second carbon fibers 35 is linear, as shown in Figures 5 and 6. 【0037】 In the first layer 20, the orientation angle of the multiple first carbon fibers 25 with respect to the axial direction DA is between 85° and 90°. The multiple first carbon fibers 25 are oriented such that they have an inner second orientation direction DL21 when observed from the radial direction DR. The inner second orientation direction DL21 is a direction that is inclined with respect to the axial direction DA by the orientation angle described above. Therefore, the angle between the inner second orientation direction DL21 and the axial direction DA is between 85° and 90°. 【0038】 In the second layer 30, the orientation angle of the multiple second carbon fibers 35 with respect to the axial direction DA is 45° or more and less than 85°. The multiple second carbon fibers 35 are oriented such that they have a second orientation direction DL2 when observed from the radial direction DR. The second orientation direction DL2 is a direction that is inclined with respect to the axial direction DA by the orientation angle described above. Therefore, the angle between the second orientation direction DL2 and the axial direction DA is 45° or more and less than 85°. 【0039】 From the viewpoint of effectively improving the durability of the cylindrical member 10 against tensile stress in the circumferential direction DC, the numerical range of the orientation angle of the multiple second carbon fibers 35 with respect to the axial direction DA is preferred in the order of 70° to 80°, 60° to 80°, and 45° to 80°. That is, among these numerical ranges for the orientation angle of the second carbon fibers 35 with respect to the axial direction DA, 70° to 80° is the most preferred. 【0040】 As shown in Figure 3, the second layer 30 may include an inner second layer 31 and an outer second layer 32 that overlap in the radial direction DR. The inner second layer 31 includes a plurality of inner second carbon fibers 36 as a plurality of second carbon fibers 35. The orientation angle of the plurality of inner second carbon fibers 36 with respect to the axial direction DA is 45° or more and less than 85°. The plurality of inner second carbon fibers 36 are oriented such that they have an inner second orientation direction DL21 when observed from the radial direction DR. The outer second layer 32 includes a plurality of outer second carbon fibers 37 as a plurality of second carbon fibers 35. The orientation angle of the plurality of outer second carbon fibers 37 with respect to the axial direction DA is 45° or more and less than 85°. The plurality of outer second carbon fibers 37 are oriented such that they have an outer second orientation direction DL22 when observed from the radial direction DR. The outer second orientation direction DL22 is symmetric with respect to the axial direction DA to the inner second orientation direction DL21. 【0041】 <Method for determining the orientation angles of multiple first carbon fibers 25> The orientation angles of multiple first carbon fibers 25 are determined by the following method. First, a sample of the cylindrical member 10 is obtained to determine the orientation angles of multiple first carbon fibers 25. If the inner circumferential surface 11 of the cylindrical member 10 is not composed of the first layer 20, the first carbon fibers 25 are exposed by machining the inner diameter of the cylindrical member 10. By exposing the first carbon fibers 25, a sample is obtained to determine the orientation angles of the first carbon fibers 25. Machining the inner diameter of the cylindrical member 10 means machining the cylindrical member 10, which rotates around the axis AS, from the inner circumferential surface 11 to the outer circumferential surface 12 using a lathe. In other words, machining the inner diameter of the cylindrical member 10 means machining the cylindrical member 10 so that the inner diameter is increased. If the first layer 20 constitutes the inner circumferential surface 11 of the cylindrical member 10, the cylindrical member 10 is used as is as a sample to determine the orientation angles. 【0042】 Next, the sample described above is cut in half by a cutting plane extending in the axial direction DA and the radial direction DR. The axis of the cylindrical member 10 sample is assumed to be located on the cutting plane. The inner surface of the halved sample is observed from the radial direction DR using an optical microscope (KEYENCE Digital Microscope VHX-950F). Specifically, as shown in Figure 4, the sample is placed on the optical microscope stage so that multiple first carbon fibers 25 are arranged in the field of view of the optical microscope. The field of view of the optical microscope is 7.1 mm × 5.3 mm. 【0043】 Next, five first carbon fibers 25 are selected from a plurality of first carbon fibers 25 observed in the field of view of the optical microscope. The optical microscope is focused so that at least five first carbon fibers 25 are clearly observable. The magnification of the optical microscope is set to 50x. For each of the five first carbon fibers 25, the angle between the longitudinal direction of the first carbon fiber 25 and the axial direction of the sample is calculated. In Figure 4, the axial direction of the sample is exemplified as axial direction DA. The average value of the calculated orientation angle for each of the five first carbon fibers 25 is taken as the measured orientation angle in that field of view. The orientation angle of the first carbon fiber 25 is the average of 10 measured values ​​obtained in 10 different fields of view. In addition, the inner second orientation direction DL21 is the direction tilted with respect to the axial direction DA by the orientation angle of the first carbon fiber 25 identified by the method described above. 【0044】 Furthermore, when determining the orientation angles of multiple first carbon fibers 25, it is assumed that multiple first carbon fibers 25 are oriented. Multiple first carbon fibers 25 are considered oriented when, in the 10 different fields of view described above, the longitudinal direction of each of the five or more first carbon fibers 25 is located within an angular range of less than 10°. 【0045】 <Method for determining the orientation angle of multiple second carbon fibers 35> The orientation angle of the second carbon fiber 35 is determined by the following method. Below, the method for determining the orientation angle of the second carbon fiber 35 will be explained in the order of the orientation angle of the outer second carbon fiber 37 and the orientation angle of the inner second carbon fiber 36. 【0046】 The orientation angle of the outer second carbon fiber 37 is determined by the following method. First, a sample of the cylindrical member 10 is obtained to determine the orientation angles of multiple outer second carbon fibers 37. If the outer circumferential surface 12 of the cylindrical member 10 is not composed of the outer second layer 32, the outer second carbon fiber 37 is exposed by machining the outer diameter of the cylindrical member 10. By exposing the outer second carbon fiber 37, a sample is obtained to determine the orientation angle of the outer second carbon fiber 37. Machining the outer diameter of the cylindrical member 10 means machining the cylindrical member 10, which rotates around the axis AS, from the outer circumferential surface 12 toward the inner circumferential surface 11 using a lathe. In other words, machining the outer diameter of the cylindrical member 10 means machining the cylindrical member 10 so that its outer diameter is reduced. If the outer second layer 32 constitutes the outer circumferential surface 12 of the cylindrical member 10, the cylindrical member 10 is used as is as a sample to determine the orientation angle. 【0047】 Next, the outer surface of the sample is observed from the radial direction (DR) using the optical microscope (KEYENCE VHX-950F digital microscope) described above. Specifically, as shown in Figure 6, the sample is placed on the optical microscope stage so that multiple outer second carbon fibers 37 are positioned in the field of view of the optical microscope. The field of view of the optical microscope is set to 7.1 mm × 5.3 mm. Five outer second carbon fibers 37 are selected from the multiple outer second carbon fibers 37 observed in the field of view of the optical microscope. The optical microscope is focused so that at least five outer second carbon fibers 37 are clearly observable. The magnification of the optical microscope is set to 50x. For each of the five outer second carbon fibers 37, the angle between the longitudinal direction of the outer second carbon fiber 37 and the axial direction of the sample is calculated. In Figure 6, the axial direction of the sample is exemplified as the axial direction (DA). The average value of the orientation angle calculations performed for each of the five outer second carbon fibers 37 is taken as the measured orientation angle in the field of view. The orientation angle of the outer second carbon fiber 37 is the average of 10 measurements taken at 10 different fields of view. The outer second orientation direction DL22 is the direction tilted with respect to the axial direction DA by the orientation angle of the outer second carbon fiber 37 determined by the method described above. 【0048】 Furthermore, when determining the orientation angles of multiple outer second carbon fibers 37, it is assumed that multiple outer second carbon fibers 37 are oriented. Multiple outer second carbon fibers 37 are considered oriented when, in the 10 different fields of view described above, the longitudinal direction of each of the five or more outer second carbon fibers 37 is located within an angular range of less than 10°. 【0049】 The orientation angle of the inner second carbon fiber 36 is determined by the following method. First, a sample of the cylindrical member 10 is obtained to determine the orientation angles of multiple inner second carbon fibers 36. The inner second carbon fibers 36 are exposed by machining the outer diameter of the cylindrical member 10. When determining the orientation angle of the inner second carbon fibers 36, the above-mentioned sample used to determine the orientation angle of the outer second carbon fiber 37 may be used instead of the cylindrical member 10. A sample for determining the orientation angle of the inner second carbon fiber 36 is obtained by machining the outer diameter. 【0050】 Next, the outer surface of the sample is observed from the radial direction (DR) using an optical microscope (KEYENCE Digital Microscope VHX-950F). Specifically, as shown in Figure 5, the sample is placed on the optical microscope stage so that multiple inner second carbon fibers 36 are positioned in the field of view of the optical microscope. The field of view of the optical microscope is set to 7.1 mm × 5.3 mm. Five inner second carbon fibers 36 are selected from the multiple inner second carbon fibers 36 observed in the field of view of the optical microscope. The optical microscope is focused so that at least five inner second carbon fibers 36 are clearly observable. The magnification of the optical microscope is set to 50x. For each of the five inner second carbon fibers 36, the angle between the longitudinal direction of the inner second carbon fiber 36 and the axial direction of the sample is calculated. In Figure 5, the axial direction of the sample is exemplified as the axial direction (DA). The average value of the orientation angle calculations performed for each of the five inner second carbon fibers 36 is taken as the measured orientation angle in the field of view. The orientation angle of the inner second carbon fiber 36 is the average of 10 measurements taken at 10 different fields of view. The inner second orientation direction DL21 is the direction tilted with respect to the axial direction DA by the orientation angle of the inner second carbon fiber 36 determined by the method described above. 【0051】 Furthermore, when determining the orientation angles of multiple inner second carbon fibers 36, it is assumed that multiple inner second carbon fibers 36 are oriented. Multiple inner second carbon fibers 36 are considered oriented when, in the 10 different fields of view described above, the longitudinal direction of each of the five or more inner second carbon fibers 36 is located within an angular range of less than 10°. 【0052】 Furthermore, the symmetry between the outer second orientation direction DL22 and the inner second orientation direction DL21 with respect to axis AS is determined by the following method: One of the directions of the inner second orientation direction DL21 and the outer second orientation direction DL22, as determined by the method described above, is reversed by an axis parallel to the axial direction DA. The angle between the reversed one direction and the other direction of the inner second orientation direction DL21 and the outer second orientation direction DL22 is measured. When the outer second orientation direction DL22 is symmetrical with respect to axis AS to the inner second orientation direction DL21, the angle measured by the above method is between 0° and 5°. 【0053】 When at least one of the orientation angles of the inner second carbon fiber 36 and the outer second carbon fiber 37, as determined by the above method, is 45° or more and less than 85°, the cylindrical member 10 includes the second layer 30 described above. Furthermore, when the following conditions (A) and (B) are met in the above determination method, the second layer 30 includes the inner second layer 31 and the outer second layer 32. (A) Both the orientation angle of the inner second carbon fiber 36 and the orientation angle of the outer second carbon fiber 37 are 45° or more and less than 85°. (B) The outer second orientation direction DL22 is symmetric with respect to axis AS with respect to the inner second orientation direction DL21. 【0054】 <<Manufacturing method for cylindrical member 10>> An example of a manufacturing method for the cylindrical member 10 shown in Figures 1 to 3 will be described. The cylindrical member 10 shown in Figure 3 is formed by heating a plurality of prepreg sheets 50 wrapped around a core material 40, as will be described later with reference to Figure 7. The core material 40 in Figure 7 has a circular cross-section centered on the axis AX (core axis AX). The core material 40 is a rod-shaped member extending in the core axis direction DB parallel to the core axis AX. The prepreg sheet 50 contains linear carbon fibers 55. In the prepreg sheet 50, a plurality of carbon fibers 55 are oriented. The prepreg sheet 50 has an orientation direction for the plurality of carbon fibers 55. The prepreg sheet 50 contains a resin composition 56 that restricts the movement of the plurality of carbon fibers 55. 【0055】 The "orientation" of multiple carbon fibers 55 in a prepreg sheet 50 can be determined by observing the prepreg sheet 50 using an optical microscope (KEYENCE Digital Microscope VHX-950F) as follows: Observe the prepreg sheet 50, which is placed on a flat surface, from the direction normal to the prepreg sheet 50 using the optical microscope described above. Observe the prepreg sheet 50 at a magnification that includes 50 to 100 linear carbon fibers 55 in one field of view. Identify the longitudinal direction of the linear carbon fibers 55 in one field of view. If, in one field of view, the longitudinal direction of each of 10 or more linear carbon fibers 55 is located within an angular range of less than 10°, then multiple carbon fibers 55 are oriented. Furthermore, the "orientation direction" of the carbon fibers 55 in the prepreg sheet 50 is the direction in which the line segment passing through the center of the angular range of the multiple carbon fibers 55 identified by the method described above extends. For example, when the angular range identified by the method described above is 1°, the orientation direction is the direction extending at an angle of 0.5° from both ends of the angular range. 【0056】 The resin composition contained in the prepreg sheet 50 may include a thermosetting resin. A thermosetting resin is typically a resin that hardens upon heating. The resin composition contained in the prepreg sheet 50 may also include a curing agent. The thermosetting resin contained in the prepreg sheet 50 may harden upon reaction with the curing agent. The thermosetting resin may include one or more of the following: phenolic resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, amino alkyd resin, melamine-urea cocondensation resin, and silicon resin. 【0057】 As shown in Figure 7, the cylindrical member 10 is manufactured from a first prepreg sheet 51, a second prepreg sheet 52, and a third prepreg sheet 53. The first layer 20 in Figure 3 is formed from the first prepreg sheet 51 in Figure 7. The first prepreg sheet 51 contains a plurality of carbon fibers 55 oriented in a first direction D1. The first direction D1 is the orientation direction of the plurality of carbon fibers 55 in the first prepreg sheet 51. The angle between the first direction D1 shown in Figure 7 and the core axis direction DB is between 85° and 90°. 【0058】 Of the second layer 30 described above, the inner second layer 31 is formed from a second prepreg sheet 52. The second prepreg sheet 52 contains a plurality of carbon fibers 55 oriented in a second direction D2. The second direction D2 is the orientation direction of the carbon fibers 55 in the second prepreg sheet 52. The angle between the second direction D2 shown in Figure 7 and the core axis direction DB is between 45° and less than 85°. 【0059】 Of the second layer 30 described above, the outer second layer 32 is formed from a third prepreg sheet 53. The third prepreg sheet 53 contains a plurality of carbon fibers 55 oriented in a third direction D3 that is non-parallel to the second direction D2. The third direction D3 is the orientation direction of the plurality of carbon fibers 55 in the third prepreg sheet 53. The angle between the third direction D3 shown in Figure 7 and the core axis direction DB is between 45° and less than 85°. 【0060】 The third direction D3 shown in Figure 7 is symmetric to the second direction D2 with respect to the axis direction DB. The symmetry of the third direction D3 with respect to the axis direction DB is determined by the following method. First, one of the directions of the second direction D2 and the third direction D3 is reversed by an axis parallel to the axis direction DB. When the angle between the reversed direction and the other direction of the second direction D2 and the third direction D3 is between 0° and 5°, the third direction D3 is symmetric to the second direction D2 with respect to the axis direction DB. 【0061】 The manufacturing method for the cylindrical member 10 includes a first winding step, a second winding step, a third winding step, and a curing step, in that order. The cylindrical member 10 may also include a pressing step before the curing step. 【0062】 First, in the first winding process, the first prepreg sheet 51 is wound around the outer surface of the core material 40. Next, in the second winding process, the second prepreg sheet 52 is wound around the outer surface of the core material 40. The second prepreg sheet 52 is wound around the outer surface of the core material 40 so as to overlap with the first prepreg sheet 51 in a direction perpendicular to the core axis direction DB. Next, in the third winding process, the third prepreg sheet 53 is wound around the outer surface of the core material 40. The third prepreg sheet 53 is wound around the outer surface of the core material 40 so as to overlap with the first prepreg sheet 51 and the second prepreg sheet 52 in a direction perpendicular to the core axis direction DB. 【0063】 In Figure 7, the dimensions of the first layer 20 in the radial direction DR are adjusted by adjusting the dimensions of the first prepreg sheet 51 in the direction perpendicular to the core axis AX. The dimensions of the inner second layer 31 in the radial direction DR are adjusted by adjusting the dimensions of the second prepreg sheet 52 in the direction perpendicular to the core axis AX. The dimensions of the outer second layer 32 in the radial direction DR are adjusted by adjusting the dimensions of the third prepreg sheet 53 in the direction perpendicular to the core axis AX. 【0064】 In Figure 7, the dimension of the first prepreg sheet 51 in the direction perpendicular to the core axis AX is larger than the dimension of the second prepreg sheet 52 in the direction perpendicular to the core axis AX. Also, the dimension of the first prepreg sheet 51 in the direction perpendicular to the core axis AX is larger than the dimension of the third prepreg sheet 53 in the direction perpendicular to the core axis AX. As a result, in the cylindrical member 10 shown in Figure 3, the dimension of the first layer 20 in the radial direction DR is larger than the dimension of the inner second layer 31 in the radial direction DR, and also larger than the dimension of the outer second layer 32 in the radial direction DR. 【0065】 Furthermore, in Figure 7, with respect to the direction perpendicular to the core axis AX, the dimensions of the first prepreg sheet 51 are larger than the sum of the dimensions of the second prepreg sheet 52 and the third prepreg sheet 53. As a result, in the cylindrical member 10 shown in Figure 3, the dimensions of the first layer 20 in the radial direction DR are larger than the dimensions of the second layer 30 in the radial direction DR. 【0066】 In the manufacturing method of the cylindrical member 10, a pressing step may be performed before the curing step. In the pressing step, the prepreg sheet 50 wound around the core material 40 is pressed toward the core material 40 in the radial direction DR. The pressing step suppresses the occurrence of gaps in the radial direction DR in the prepreg sheet 50 wound around the core material 40. In the manufacturing method of the cylindrical member 10, which includes a first winding step, a second winding step, and a third winding step, the pressing step is performed between the third winding step and the curing step. In the pressing step, a release film for pressing the prepreg sheet 50 in the radial direction DR may be wound around the core material 40 so as to overlap the prepreg sheet 50. 【0067】 Next, in the curing process, the first prepreg sheet 51, the second prepreg sheet 52, and the third prepreg sheet 53 are cured. The first prepreg sheet 51, the second prepreg sheet 52, and the third prepreg sheet 53 may also be cured by heating while they are wound around the core material 40. The first prepreg sheet 51, the second prepreg sheet 52, and the third prepreg sheet 53 are cured while they are wound around the core material 40. 【0068】 After the curing process, the core material 40 is removed to obtain a cylindrical member extending in the axial direction DA. After the curing process, the release film may be peeled off by the pressing process described above. By cutting this cylindrical member at predetermined intervals in the axial direction DA, cylindrical members 10 as shown in Figures 1 and 2 are obtained. In this way, the cylindrical members 10 shown in Figures 1 to 3 are manufactured. 【0069】 Next, the function of the cylindrical member 10 shown in Figures 1 to 3 will be explained, mainly with reference to Figure 8. Specifically, the method for evaluating the durability of the illustrated cylindrical member 10 against tensile stress in the circumferential direction DC will be explained, mainly with reference to Figure 8. 【0070】 Figure 8 shows a jig 100 for evaluating the durability of a cylindrical member 10 against tensile stress in the circumferential direction DC. The jig 100 includes an expanding member 110, a first housing member 120, and a second housing member 130. The expanding member 110, the first housing member 120, and the second housing member 130 may be made of metal. 【0071】 <Expanding member 110> The diameter-expanding member 110 shown in Figure 8 has a rotational shape centered on the axis AL. The diameter-expanding member 110 has a first bottom surface 111 and a second bottom surface 112 as end faces in a direction parallel to the axis AL. The diameter-expanding member 110 has a side surface 113 between the first bottom surface 111 and the second bottom surface 112 as an outer circumferential surface. 【0072】 As shown in Figure 8, the outer diameter of the diameter-expanding member 110 expands from the first bottom surface 111 to the second bottom surface 112. In other words, the diameter-expanding member 110 expands in diameter from the first bottom surface 111 to the second bottom surface 112. To put it another way, the diameter-expanding member 110 has a tapered shape. As the diameter-expanding member 110 expands in diameter, the side surface 113 is inclined with respect to the axis AL. The inclination angle φ of the side surface 113 with respect to the axis AL is, for example, 2.0°. 【0073】 <First housing member 120> The first housing member 120 in Figure 8 is a cylindrical member centered on the axis AM. The first housing member 120 has a first bottom surface 121 and a second bottom surface 122 as end faces in a direction parallel to the axis AM. The first housing member 120 is in contact with the second member 202 of the compression testing machine, which will be described later, at the first bottom surface 121. The second housing member 130, which will be described later, is in contact with the second bottom surface 122. The first housing member 120 supports the second housing member 130 and the cylindrical member 10 held by the second housing member 130 at the second bottom surface 122. 【0074】 The first housing member 120 in Figure 8 is provided with first through holes 125 that open on both end faces in a direction parallel to the axis AM. The inner diameter of the first housing member 120, i.e., the outer diameter of the first through holes 125, is larger than the outer diameter of the expanding member 110 at the end of the expanding member 110 on the first bottom surface 111 side. As a result, the first through holes 125 can accommodate the expanding member 110, as shown in Figure 8. The total length of the first housing member 120 in the direction parallel to the axis AM may be larger than the total length of the expanding member 110 in the direction parallel to the axis AL. The inner diameter of the first housing member 120 may be larger than the outer diameter of the expanding member 110 at the end of the expanding member 110 on the second bottom surface 112 side. As a result, the first through holes 125 may be able to accommodate the expanding member 110 over its entire length in the direction parallel to the axis AL. 【0075】 <Second housing member 130> The second housing member 130 in Figure 8 has a rotational shape about axis AN. The second housing member 130 includes a plurality of second housing member elements that are equally divided in the circumferential direction about axis AN. As an example, the second housing member 130 is divided into eight equal parts in the circumferential direction about axis AN. In this example, the second housing member 130 includes eight second housing member elements. The second housing member 130 has a first bottom surface 131 and a second bottom surface 132 as end faces in a direction parallel to axis AN. 【0076】 The second housing member 130 in Figure 8 is provided with second through holes 135 that open on both end faces in a direction parallel to the axis AN. The outer diameter of the illustrated second through hole 135 expands from the first bottom surface 131 to the second bottom surface 132. In other words, the second through hole 135 expands in diameter from the first bottom surface 131 to the second bottom surface 132. Due to the expansion of the second through hole 135, the inner circumferential surface of the second housing member 130 is inclined with respect to the axis AN. The inclination angle of the inner circumferential surface of the second housing member 130 with respect to the axis AN is equal to the inclination angle φ of the side surface 113 with respect to the axis AL. The illustrated second through hole 135 houses the enlarged diameter member 110. The enlarged diameter member 110 is in contact with the second housing member 130 on the side surface 113 from a direction perpendicular to the axis AL. 【0077】 As described above, the outer diameter of the second housing member 130 changes according to the outer diameter of the enlarged member 110 housed in the second through hole 135, as the second housing member 130 is divided equally in the circumferential direction centered on the axis AN. The outer diameter of the second housing member 130 increases as the outer diameter of the enlarged member 110 housed in the second through hole 135 increases. 【0078】 The second housing member 130 in Figure 8 has a support surface 133 that supports the cylindrical member 10 and a contact surface 134 that contacts the inner circumferential surface 11 of the cylindrical member 10 from the radial direction DR. As described above, the outer diameter of the second housing member 130 changes in accordance with the change in the outer diameter of the enlarged member 110 housed in the second through hole 135. The outer diameter of the second housing member 130 changes while the cylindrical member 10 is supported by the support surface 133. As the outer diameter of the second housing member 130 increases, the cylindrical member 10 is pulled in the circumferential direction DC while supported by the support surface 133 and in contact with the contact surface 134. A tensile stress in the circumferential direction DC acts on the cylindrical member 10 as the outer diameter of the second housing member 130 increases while it is supported by the support surface 133 and in contact with the contact surface 134. 【0079】 The jig 100 having the above configuration is placed inside a compression testing machine. In the compression testing machine, the jig 100 is placed between the first member 201 and the second member 202. The compression testing machine compresses the jig 100 placed between the first member 201 and the second member 202. As such a compression testing machine, the universal testing machine "5582" manufactured by Instron Japan Company Limited is used. The jig 100 is placed between the first member 201 and the second member 202 with the cylindrical member 10 held in the second housing member 130. The compression testing machine compresses the jig 100 by pressing the first member 201 toward the second member 202. The compression testing machine can detect the compression load W when compressing the jig 100. The compression testing machine can also detect the amount of displacement L of the first member 201 toward the second member 202 after the start of compression of the jig 100. 【0080】 When the compression testing machine compresses the jig 100 in Figure 8, the first member 201 contacts the second bottom surface 112 of the diameter-expanding member 110. When the compression testing machine compresses the jig 100, the diameter-expanding member 110 is pushed by the first member 201 toward the second member 202 in a direction parallel to the axis AL. With the diameter-expanding member 110 in contact with the second housing member 130 at its side surface 113, it pushes the second housing member 130 toward the axis AL in the direction normal to the side surface 113. The second housing member 130, together with the cylindrical member 10 supported on the support surface 133, is pulled toward the axis AM in a direction perpendicular to the axis AM. The cylindrical member 10 supported on the support surface 133 is pulled toward the circumferential direction DC as a result of the second housing member 130 being pulled in this way. Therefore, the cylindrical member 10 in Figure 8 is pulled in the circumferential direction DC by the compression of the jig 100 by the compression testing machine. 【0081】 As the compression testing machine further compresses the jig 100, the diameter-expanding member 110 moves in a direction parallel to the axis AL relative to the first housing member 120 and the second housing member 130. The diameter-expanding member 110 moves toward the first housing member 120 and the second housing member 130 from the first member 201 toward the second member 202. As described above, the side surface 113 of the diameter-expanding member 110 expands in diameter from the first bottom surface 111 toward the second bottom surface 112. Therefore, the movement of the diameter-expanding member 110 increases the outer diameter of the portion of the diameter-expanding member 110 that contacts the second housing member 130 (contact surface 134). The increase in the outer diameter of the diameter-expanding member 110 also increases the outer diameter of the second housing member 130. As a result of the increase in the outer diameter of the second housing member 130, a tensile stress in the circumferential direction DC acts on the cylindrical member 10, as described above. The cylindrical member 10 fractures when the tensile stress acting in the radial direction DR exceeds the allowable value. The durability of the cylindrical member 10 against tensile stress in the circumferential direction DC is evaluated by comparing the magnitude of the compressive load W at the time of fracture. 【0082】 Furthermore, based on the evaluation of the cylindrical member 10 described above, the diameter expansion amount L of the cylindrical member 10 can be determined. rm The amount of diameter expansion L can be calculated. rm This is the displacement L of the first member 201 from the time the compression testing machine starts compressing the jig 100 until the cylindrical member 10 breaks. m Therefore, it can be calculated by the following equation (1). In equation (1), φ is the inclination angle of the side surface 113 of the enlarged diameter member 110 with respect to the axis AL. Also, the maximum strain of the cylindrical member 10 is the amount L of the enlarged diameter of the cylindrical member 10. rm And the inner diameter D of the cylindrical member 10 can be determined by the following formula (2). 【number】 【number】 【0083】 Incidentally, the expanding range of applications for motors has led to a demand for higher motor output. To achieve higher motor output, an increase in the rotational speed of the rotor relative to the stator is required. The rotor includes a rotor body and magnets attached to the rotor body. As mentioned above, it is expected that a cylindrical member covering the rotor from the outside in a direction perpendicular to the axis of rotation will prevent the magnets from falling off the rotor body. 【0084】 In a cover rotor that rotates relative to the stator, the cylindrical member, like the magnet, is subjected to centrifugal force as an inertial force. The cylindrical member rotating relative to the stator is pulled circumferentially by the centrifugal force. In other words, the cylindrical member rotating relative to the stator is subjected to circumferential tensile stress due to the centrifugal force. As the rotor's rotational speed increases, the circumferential tensile stress acting on the cylindrical member also increases. The cylindrical member fractures when the circumferential tensile stress exceeds the allowable value. When the cylindrical member fractures, the aforementioned function of the cylindrical member, namely its function of preventing the magnet from falling off the rotor body, is lost. To ensure stable high-speed rotation of the cover rotor, it is necessary to improve the circumferential tensile stress in the cylindrical member. 【0085】 In contrast, the cylindrical member 10 shown in Figures 1 to 3 includes a first layer 20 and a second layer 30 in that order, from the inner circumferential surface 11 to the outer circumferential surface 12. The first layer 20 contains a plurality of first carbon fibers 25. The orientation angle of the plurality of first carbon fibers 25 with respect to the axial direction DA is 85° or more and 90° or less. The second layer 30 contains a plurality of second carbon fibers 35. The orientation angle of the plurality of second carbon fibers 35 with respect to the axial direction DA is 45° or more and less than 85°. Such a cylindrical member 10 can improve durability against tensile stress in the radial direction DR, as shown in the embodiments described later. Specifically, as shown in the embodiments described later, the compressive load W at the time of fracture of the cylindrical member 10 can be improved. 【0086】 In the cylindrical member 10, an upper limit may be set for the maximum strain in the radial direction DR. The maximum strain is the ratio of the maximum amount of diameter expansion of the cylindrical member to the outer diameter of the cylindrical member before measuring the tensile stress described above. In the cylindrical member, the maximum amount of diameter expansion is the difference between the maximum value of the outer diameter before fracture, measured when measuring the tensile stress described above, and the value of the outer diameter before measuring the tensile stress. The maximum strain may be 0.025 or less, 0.020 or less, or 0.019 or less. By setting such an upper limit for the maximum strain, outward deformation of the cylindrical member 10 in the radial direction DR is suppressed. This prevents the expanded cylindrical member 10 from rotating while in contact with the stator 2 between the rotor 4 and the stator 2. Therefore, the rotational motion of the cover rotor 3 relative to the stator 2 can be stabilized. 【0087】 In the cylindrical member 10, a lower limit may be set for the maximum strain. The maximum strain may be 0.010 or higher, 0.015 or higher, or 0.017 or higher. By setting such a lower limit for the maximum strain, fracture of the cylindrical member 10 due to tensile stress in the radial direction DR can be suppressed. 【0088】 In the embodiment described above, the cylindrical member 10 includes a first layer 20 and a second layer 30 in that order, from the inner circumferential surface 11 to the outer circumferential surface 12. The first layer 20 includes a plurality of first carbon fibers 25. The orientation angle of the plurality of first carbon fibers 25 with respect to the axial direction DA is 85° or more and 90° or less. The second layer 30 includes a plurality of second carbon fibers 35. The orientation angle of the plurality of second carbon fibers 35 with respect to the axial direction DA is 45° or more and less than 85°. According to this embodiment, the durability of the cylindrical member 10 against tensile stress in the circumferential direction DC can be improved. As a result, stable high-speed rotation can be achieved in the cover rotor 3 including the cylindrical member 10. [Examples] 【0089】 An embodiment of the present invention will be described in more detail below using examples. The present invention is not limited to the following examples. 【0090】 Cylindrical members according to Examples 1 to 5 and cylindrical members according to Comparative Examples 1 to 3 were manufactured by the manufacturing method described above. The manufactured cylindrical members had an inner circumferential surface and an outer circumferential surface. The cylindrical members according to Examples 1 to 5 and the cylindrical members according to Comparative Examples 2 and 3 contained a first layer and a second layer in that order, from the inner circumferential surface toward the outer circumferential surface. The cylindrical members according to Examples 1 to 5 and the cylindrical members according to Comparative Examples 2 and 3 contained an inner second layer and an outer second layer that overlapped radially in the second layer. 【0091】 <Example 1> The cylindrical member according to Example 1 was manufactured from a first prepreg sheet, a second prepreg sheet, and a third prepreg sheet using the manufacturing method described above. When manufacturing the cylindrical member according to Example 1, the angle between the orientation direction of the multiple carbon fibers in the first prepreg sheet, i.e., the first direction and the core axis direction, was 90°. When manufacturing the cylindrical member according to Example 1, the angle between the orientation direction of the multiple carbon fibers in the second prepreg sheet, i.e., the second direction and the core axis direction, was 45°. When manufacturing the cylindrical member according to Example 1, the angle between the orientation direction of the multiple carbon fibers in the third prepreg sheet, i.e., the third direction and the core axis direction, was 45°. When manufacturing the cylindrical member according to Example 1, the third direction was symmetrical with respect to the second direction and the core axis direction. The inner diameter of the cylindrical member according to Example 1 was 28.8 mm. The cylindrical member according to Example 1 had a thickness of 1 mm in the radial direction. In the cylindrical member according to Example 1, the first layer had a thickness of 0.810 mm in the radial direction. In the cylindrical member according to Example 1, the second layer had a thickness of 0.162 mm in the radial direction. The thickness of the first layer in the radial direction of the cylindrical member according to Example 1 was five times the thickness of the second layer in the radial direction. 【0092】 <Example 2> The cylindrical member according to Example 2 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When manufacturing the cylindrical member according to Example 2, the angle between the second direction and the core axis direction in the second prepreg sheet was 50°. When manufacturing the cylindrical member according to Example 2, the angle between the third direction and the core axis direction in the third prepreg sheet was 50°. When manufacturing the cylindrical member according to Example 2, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Example 2, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 50°. The cylindrical member according to Example 2 had the same configuration as the cylindrical member according to Example 1 in respect to all other points except the orientation angle of the second layer. 【0093】 <Example 3> The cylindrical member according to Example 3 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When manufacturing the cylindrical member according to Example 3, the angle between the second direction and the core axis direction in the second prepreg sheet was 60°. When manufacturing the cylindrical member according to Example 3, the angle between the third direction and the core axis direction in the third prepreg sheet was 60°. When manufacturing the cylindrical member according to Example 3, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Example 3, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 60°. The cylindrical member according to Example 3 had the same configuration as the cylindrical member according to Example 1 in respect to all other points except the orientation angle of the second layer. 【0094】 <Example 4> The cylindrical member according to Example 4 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When manufacturing the cylindrical member according to Example 4, the angle between the second direction and the core axis direction in the second prepreg sheet was 70°. When manufacturing the cylindrical member according to Example 4, the angle between the third direction and the core axis direction in the third prepreg sheet was 70°. When manufacturing the cylindrical member according to Example 4, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Example 4, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 70°. The cylindrical member according to Example 4 had the same configuration as the cylindrical member according to Example 1 in respect to all other points except the orientation angle of the second layer. 【0095】 <Example 5> The cylindrical member according to Example 5 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When manufacturing the cylindrical member according to Example 5, the angle between the second direction and the core axis direction in the second prepreg sheet was 80°. When manufacturing the cylindrical member according to Example 5, the angle between the third direction and the core axis direction in the third prepreg sheet was 80°. When manufacturing the cylindrical member according to Example 5, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Example 5, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 80°. The cylindrical member according to Example 5 had the same configuration as the cylindrical member according to Example 1 in respect to all other points except the orientation angle of the second layer. 【0096】 <Comparative Example 1> The cylindrical member according to Comparative Example 1 differed from the cylindrical member according to Example 1 in its layer configuration. The cylindrical member according to Comparative Example 1 was made from only the first prepreg sheet. When manufacturing the cylindrical member according to Comparative Example 1, the angle between the first direction and the core axis direction in the first prepreg sheet was 90°. The cylindrical member according to Example 4 did not include a second layer. The cylindrical member according to Comparative Example 1 had the same configuration as the cylindrical member according to Example 1 in respects other than the layer configuration of the cylindrical member. 【0097】 <Comparative Example 2> The cylindrical member according to Comparative Example 2 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When the cylindrical member according to Comparative Example 2 was manufactured, the angle between the second direction and the core axis direction in the second prepreg sheet was 30°. When the cylindrical member according to Comparative Example 2 was manufactured, the angle between the third direction and the core axis direction in the third prepreg sheet was 30°. When the cylindrical member according to Comparative Example 2 was manufactured, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Comparative Example 2, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 30°. The cylindrical member according to Comparative Example 2 had the same configuration as the cylindrical member according to Example 1 in respect to all other points except the orientation angle of the second layer. 【0098】 <Comparative Example 3> The cylindrical member according to Comparative Example 3 differed from the cylindrical member according to Example 1 in the orientation angle of the second layer. When the cylindrical member according to Comparative Example 3 was manufactured, the angle between the second direction and the core axis direction in the second prepreg sheet was 20°. When the cylindrical member according to Comparative Example 3 was manufactured, the angle between the third direction and the core axis direction in the third prepreg sheet was 20°. When the cylindrical member according to Comparative Example 3 was manufactured, the third direction was symmetrical with respect to the second direction and the core axis direction. In the cylindrical member according to Comparative Example 3, the orientation angles of the inner second layer and the outer second layer with respect to the axis direction were 20°. The cylindrical member according to Comparative Example 3 had the same configuration as the cylindrical member according to Example 1 in respects other than the orientation angle of the second layer. 【0099】 <Orientation angle> For the cylindrical members according to Examples 1 to 5 and the cylindrical members according to Comparative Examples 1 to 3, the orientation angle of the first layer described above is shown in the "First Layer Orientation Angle (°)" column of Table 1. For the cylindrical members according to Examples 1 to 5 and the cylindrical members according to Comparative Examples 2 to 3, the orientation angle of the inner second layer described above is shown in the "Inner Second Layer Orientation Angle (°)" column of Table 1. For the cylindrical members according to Examples 1 to 5 and the cylindrical members according to Comparative Examples 2 to 3, the orientation angle of the outer second layer described above is shown in the "Outer Second Layer Orientation Angle (°)" column of Table 1. Note that the notation "-" in the "Inner Second Orientation Angle (°)" and "Outer Second Orientation Angle (°)" for the cylindrical member according to Comparative Example 1 means that the cylindrical member did not contain either an inner second layer or an outer second layer. 【0100】 <Compressive load and maximum strain at fracture> Using the cylindrical members from Examples 1 to 5 and the cylindrical members from Comparative Examples 1 to 3, the compressive load and maximum strain at fracture were determined by the method described above. A universal testing machine "5582" manufactured by Instron Japan Company Limited was used to determine the compressive load and maximum strain at fracture. The compressive load at fracture of the cylindrical members is shown in the "Compressive Load (kN)" column of Table 1. The determined maximum strain is shown in the "Maximum Strain" column of Table 1. As shown in Table 1, the compressive load at fracture of the cylindrical members from Examples 1 to 5 increased compared to the cylindrical members from Comparative Examples 1 to 3. 【0101】 [Table 1] 【0102】 Although one embodiment has been described with reference to specific examples, the above-mentioned example does not limit this embodiment. The above-described embodiment can be implemented in various other examples, and various omissions, substitutions, modifications, and additions can be made without departing from its essence. 【0103】 In the cylindrical member 10 described above, the second layer 30 included an inner second layer 31 and an outer second layer 32 that overlapped in the radial direction DR. The second layer 30 may include multiple inner second layers 31 and multiple outer second layers 32, as shown in Figure 10. In the second layer 30 of Figure 10, the inner second layer 31 and the outer second layer 32 overlap alternately in the radial direction DR. 【0104】 The manufacturing method for the cylindrical member 10 described above includes a first winding step, a second winding step, and a third winding step. The manufacturing method for the cylindrical member 10 may include a joining step instead of the third winding step. The joining step is performed before the second winding step. In the joining step, the third prepreg sheet 53 described above is joined to the second prepreg sheet 52. In the second winding step, the second prepreg sheet 52 and the third prepreg sheet 53, which have been joined to each other, are wound around the core material 40. The joining step may be performed before the first winding step, or between the first and second winding steps. 【0105】 The method for manufacturing the cylindrical member 10 may include, in this order, a joining step of joining a plurality of prepreg sheets 50, and a winding step of winding the plurality of prepreg sheets 50 joined together onto a core material 40. The method for manufacturing the cylindrical member 10 may also include a joining step of joining a first prepreg sheet 51 and a second prepreg sheet 52, a winding step of winding the first prepreg sheet 51 and the second prepreg sheet 52 onto the outer surface of the core material 40, and a curing step of curing the first prepreg sheet 51 and the second prepreg sheet 52. [Explanation of symbols] 【0106】 1: Motor, 2: Stator, 3: Cover rotor, 4: Rotor, 5: Rotor body, 6: Magnet, 10: Cylindrical member, 11: Inner circumferential surface, 12: Outer circumferential surface, 20: First layer, 25: First carbon fiber, 30: Second layer, 31: Inner second layer, 32: Outer second layer, 35: Second carbon fiber, 36: Inner second carbon fiber, 37: Outer second carbon fiber, 40: Core material, 50: Prepreg sheet, 51: First prepreg sheet, 52: Second prepreg sheet, 53: Third prepreg sheet, DA: Axial direction, DC: Circumferential direction, DR: Radial direction

Claims

[Claim 1] A cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, The first and second layers are arranged in this order, from the inner surface toward the outer surface. The first layer includes a plurality of first carbon fibers having an orientation angle of 85° or more and 90° or less with respect to the axial direction parallel to the axis of the cylindrical member. The second layer is a cylindrical member comprising a plurality of second carbon fibers having an orientation angle of 45° or more and less than 85° with respect to the axial direction. [Claim 2] The cylindrical member according to claim 1, wherein the thickness of the first layer in the radial direction perpendicular to the axis is greater than the thickness of the second layer in the radial direction. [Claim 3] The cylindrical member according to claim 1, wherein the maximum strain in the radial direction perpendicular to the axis is 0.010 or more and 0.025 or less. [Claim 4] The second layer includes an inner second layer and an outer second layer that overlap radially perpendicular to the axis, The inner second layer comprises a plurality of inner second carbon fibers oriented such that they have an inner second orientation direction when viewed from the radial direction. The cylindrical member according to claim 1, wherein the outer second layer includes a plurality of outer second carbon fibers oriented such that, when viewed from the radial direction, it has an outer second orientation direction symmetric with respect to the axis with respect to the inner second orientation direction. [Claim 5] A method for manufacturing a cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, A first winding step involves winding a first prepreg sheet containing multiple carbon fibers oriented in a first direction around the outer surface of a core material, A second winding step involves winding a second prepreg sheet containing a plurality of carbon fibers oriented in a second direction onto the core material so as to overlap the first prepreg sheet. The process includes a curing step for curing the first prepreg sheet and the second prepreg sheet, The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. A method for manufacturing a cylindrical member, wherein the angle between the second direction and the axis direction is 45° or more and less than 85°. [Claim 6] A third winding step performed between the second winding step and the curing step, further comprising a third winding step in which a third prepreg sheet containing a plurality of carbon fibers oriented in a third direction is wound around the core material so as to overlap the second prepreg sheet, In the curing step, the first prepreg sheet, the second prepreg sheet, and the third prepreg sheet are cured. The method for manufacturing a cylindrical member according to claim 5, wherein the third direction is symmetric with respect to the second direction and the axis direction. [Claim 7] A bonding step performed prior to the second winding step, further comprising a bonding step of bonding a third prepreg sheet containing a plurality of carbon fibers oriented in a third direction to the second prepreg sheet, The third direction is symmetrical with respect to the second direction and the axis direction, The method for manufacturing a cylindrical member according to claim 5 or 6, wherein in the second winding step, the second prepreg sheet and the third prepreg sheet are wound around the core material. [Claim 8] A method for manufacturing a cylindrical member that covers the rotor of a motor from a direction perpendicular to the rotation axis of the rotor, A bonding step of joining a first prepreg sheet containing a plurality of carbon fibers oriented in a first direction and a second prepreg sheet containing a plurality of carbon fibers oriented in a second direction, A winding step in which the first prepreg sheet and the second prepreg sheet are wound around the outer surface of the core material, The process includes a curing step for curing the first prepreg sheet and the second prepreg sheet, The angle between the first direction and the core axis direction parallel to the axis of the core material is 85° or more and 90° or less. A method for manufacturing a cylindrical member, wherein the angle between the second direction and the axis direction is 45° or more and less than 85°.

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