Arm and projectile

Abstract

Provided is an arm that includes at least one fiber-reinforced resin layer, wherein the fiber-reinforced resin layer includes reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated in the reinforcing fibers, and satisfies the following condition I or condition II when the longitudinal direction of the arm is set to 0°: I: Includes two or more layers selected from the group consisting of the following layers A to C; II: Includes the following layer B; Layer A: A layer in which the orientation angle of the reinforcing fibers is greater than -3° to less than +3°; Layer B: A layer in which the orientation angle of the reinforcing fibers is -35° to -3°, and / or +3° to +35°; Layer C: A layer in which the orientation angle of the reinforcing fibers is -80° to less than -35°, and / or greater than +35° to +80°.

Description

Arm and Flying Vehicle

[0001] The present disclosure relates to an arm, a flying vehicle, and the like.

[0002] Conventional flying vehicles include, for example, drones, airplanes, manned helicopters, radio-controlled unmanned helicopters, and the like. Among them, a drone is known to include a housing in which a battery and the like are disposed, a plurality of rotors for causing the drone to fly, and an arm for holding the rotor at a position outside the housing and away from the housing (see, for example, Patent Document 1).

[0003] Patent Document 1 describes, as an example of a drone arm, a cylindrical arm whose cylindrical wall is formed of a laminated structure obtained by laminating a plurality of fiber-reinforced resin sheets woven with fibers (that is, fiber-reinforced resin woven fabric sheets). Patent Document 1 also describes that an arm obtained by molding the above laminated structure is lightweight and has high rigidity.

[0004] Japanese Patent Application Laid-Open No. 2018-118530

[0005] As described in Patent Document 1, using a fiber-reinforced resin woven fabric sheet as an arm material can increase the rigidity of the arm while reducing the weight thereof. On the other hand, from the viewpoint of flight stability of the flying vehicle, the arm may also be required to have a characteristic of suppressing vibration generated by the rotor.

[0006] The present disclosure has been made in view of the above problems of the prior art, and an object thereof is to provide an arm with improved vibration suppression performance and a flying vehicle including the arm.

[0007] One aspect of the present disclosure is listed below: (1) An arm comprising at least one fiber-reinforced resin layer, wherein the fiber-reinforced resin layer comprises reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated in the reinforcing fibers, and the fiber-reinforced resin layer satisfies the following conditions I or II when the longitudinal direction of the arm is 0°: Condition I: comprising two or more layers selected from the group consisting of the following layers A to C; Condition II: comprising the following layer B; Layer A: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is greater than -3° and less than +3°; Layer B: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is between -35° and -3°, and / or between +3° and +35°; Layer C: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is between -80° and less than -35°, and / or between +35° and +80°; (2) The arm according to item 1, wherein the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer of layer C is -45° or more and less than -35°, and / or greater than +35° and less than or equal to +45°. (3) The arm according to item 1 or 2, comprising layer A and layer B. (4) The arm according to item 3, wherein the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer of layer B is -15° or more and less than -3°, and / or greater than or equal to +3° and less than or equal to +15°. (5) The arm according to any one of items 1 to 4, wherein the thickness of layers A and B in the fiber-reinforced resin layer is 25% or more in the thickness direction relative to the entire fiber-reinforced resin layer. (6) The arm according to any one of items 1 to 5, wherein when the arm is divided into an outer region and a central region from the center of the thickness direction of the arm, the proportion of layer A and layer B is greater in the outer region than in the central region. (7) An arm according to any one of items 1 to 6, wherein, except for the center of the fiber-reinforced resin layer lamination, the orientation angles of the reinforcing fibers of adjacent fiber-reinforced resin layers in the thickness direction are different. (8) An arm according to any one of items 1 to 7, wherein the fiber-reinforced resin layer is symmetrically laminated. (9) An arm according to any one of items 1 to 8, which does not include a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is -90° or more and less than -80°, and / or greater than +80° and less than or equal to +90°.(10) An arm according to any one of items 1 to 8, wherein the fiber-reinforced resin layer does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -45°, and / or greater than +45° and less than or equal to +90°. (11) An arm according to any one of items 1 to 8, wherein the fiber-reinforced resin layer does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -35°, and / or greater than +35° and less than or equal to +90°. (12) An arm according to any one of items 1 to 11, wherein the fiber-reinforced resin layer is layer B. (13) An arm according to any one of items 1 to 12, wherein a drive body for rotating a rotor is installed at the tip of the arm. (14) A flying object comprising an arm according to any one of items 1 to 13.

[0008] According to this disclosure, an arm with enhanced vibration suppression and a flying object having the arm are provided.

[0009] Figure 1 is a perspective view showing the arm's appearance when viewed from an oblique upward direction. Figure 2 is a schematic partial cross-sectional view when the arm is cut along the line segment A-A in Figure 1, showing either an arm with a generally flat bottom (a) or an arm with an open bottom (b). Figure 3 is a side view showing the overall structure of the arm. Figure 4 is a schematic diagram showing the appearance of the flying object.

[0010] In this disclosure, the numerical range indicated using "~" means the range that includes the numbers written before and after "~" as the minimum and maximum values, respectively.

[0011] In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages.

[0012] <Arm> In one aspect of the present disclosure, an arm is provided which includes at least one fiber-reinforced resin layer. The arm is a member having a generally linear or rod-like shape.

[0013] The arm can optionally hold, at one end, a drive unit that rotates a rotor, such as a rotor blade, and at the other end, a housing, box, platform, plate-shaped member, etc. In one example, the arm creates a predetermined distance between the rotor and the housing, thereby preventing the rotating rotor from colliding with the housing. The arm may also be bent or flexed in the middle. Furthermore, the arm may extend outward from the center of gravity of the housing, or in a direction that has a predetermined angle with respect to the direction outward from the center of gravity of the housing.

[0014] In another example, the arm can hold a component other than the rotor unit at its tip. Specifically, the arm may hold a camera, a light-emitting component (such as an LED), or an additional robotic arm at its tip.

[0015] The arm may optionally have layers other than the fiber-reinforced resin layer, such as a resin layer without reinforcing fibers, a base material, a layer made only of resin (e.g., a surface protection layer, an adhesive layer, etc.), a layer or base material without resin, a metal layer, etc.

[0016] The arms of this disclosure are illustrated in Figures 1, 2, and 3, but are not limited thereto. Figures 1 to 3 are schematic, and the arms of this disclosure are not limited to the scale or dimensions shown in the figures and are capable of various modifications.

[0017] Figure 1 is a perspective view showing the arm's appearance when viewed from an oblique upward direction. Figure 2 is a partial cross-sectional view of the arm when it is cut along the line segment A-A in Figure 1. Figure 3 is a side view showing the overall structure of the arm.

[0018] As shown in Figures 1 and 3, the upper surface of the arm 100 may have a generally flat area and / or a rounded area.

[0019] As shown in Figure 2(a), the arm 100 may have a shape with a generally flat bottom surface along the vertical direction (z), such as a block or plate shape, or as shown in Figure 2(b), it may have a shape with an open bottom surface, such as a semi-cylindrical, hat-shaped, bowl-shaped, U-shaped, or C-shaped shape. Furthermore, from the viewpoint of facilitating molding, it is preferable that the cross-sectional shape perpendicular to the longitudinal direction of the arm is an open cross-section with a part of the cross-section open, rather than a closed cross-section such as a cylinder. For example, if the cross-section is an open cross-section, it can be molded by press molding or the like.

[0020] As shown in Figures 1 and 3, the arm 100 may have a main body portion 110 and a flange 120 positioned on the outside of the main body portion 110, or it may have only the main body portion 110 (not shown). If the arm 100 has a flange 120, the flange 120 can extend from the lower end of the side surface of the main body portion 110 in the width direction (y) of the main body portion 110 along the longitudinal direction of the main body portion 110. The main body portion 110 and the flange 120 can be integrally molded or connected via a connecting portion. From the viewpoint of balancing the rigidity and weight reduction of the arm 100, integral molding using fiber-reinforced resin is preferred.

[0021] The main body 110 may have a shape with a generally flat bottom surface, such as a block or plate shape, as shown in Figure 2(a), or a shape with an open bottom surface, such as a semi-cylindrical, hat-shaped, bowl-shaped, U-shaped, or U-shaped shape, as shown in Figure 2(b).

[0022] The main body 110 may be a rod-shaped object of any form, such as a triangular prism, a square prism, a hexagonal prism, a cylinder, an elliptical prism, or a semi-cylindrical shape with a bent surface. In any of these shapes, at least one of the faces along the longitudinal direction (x) may be open, or it may not have to have any open faces along the longitudinal direction (x).

[0023] As shown in Figures 1 and 3, the main body 110 may have a base portion 130 for attaching the arm 100 to a first external member, an extension portion 140 extending outward from the base portion 130, and a tip portion 150 for arranging a second external member connected to the tip of the extension portion 140. The first and second external members can be determined according to the application of the arm 100. In one example, the first external member is a housing and the second external member is a rotor unit.

[0024] The base portion 130 and the extended portion 140 can be integrally molded or connected via a connecting portion. The extended portion 140 and the tip portion 150 can be integrally molded or connected via a connecting portion. From the viewpoint of balancing the rigidity and weight reduction of the arm 100, integral molding of the base portion 130, the extended portion 140 and the tip portion 150 is preferred using fiber-reinforced resin.

[0025] The base portion 130 is the part for attaching the arm 100 to the first external member. In one example, the base portion 130 is attached to the housing by inserting fastening screws into fastening holes 120a formed in the flange 120. A base wall 130a is formed on the side of the base portion 130 that contacts the housing. An opening 130b is formed in the base wall 130a to allow wiring from the mounting portion to enter the inside of the outer shell of the base portion 130.

[0026] From the viewpoint of rigidity for supporting the weight of the arm 100 and the second external member, the base portion 130 preferably has a flange 120. The flange 120 on the base portion 130 can be used as a fastening point and can also increase the rigidity of the base portion 130. Furthermore, by using the flange 120 as a fastening point, drilling holes in the main body portion 110 is unnecessary, and the reduction in rigidity of the main body portion 110 due to drilling can also be suppressed.

[0027] The extension portion 140 is a connecting portion that connects the base portion 130 and the tip portion 150 in a linear or rod-like manner. From the viewpoint of rigidity of the arm 100, the extension portion 140 may have approximately the same cross-sectional area, height, or width, or from the viewpoint of balancing weight reduction and rigidity of the arm 100, it may have a shape in which the cross-sectional area becomes smaller, the height decreases, or the width becomes narrower towards the tip portion 150. The extension portion 140 may also have a bent or flexed shape in the middle.

[0028] As shown in Figure 3, the extension portion 140 preferably has a shape in which the height relative to the reference first external member increases from the base portion 130 towards the tip portion 150, from the viewpoint of the distance between the first external member and the second external member, the center of gravity or mass of both members, and the vibration suppression performance of the arm 100. It is more preferable that the angle θ between the wall surface direction of the base wall 130a and the upper surface direction of the tip portion 150 is in the range of 80° to 100°, and even more preferable that the angle θ is approximately 90°.

[0029] As shown in Figure 3, the angle of the upper surface of the arm 100 can differ between the extension portion 140 and the tip portion 150. Specifically, the extension portion 140 can be formed so that its upper surface is tilted upward in order to raise the position of the tip portion 150. On the other hand, the tip portion 150 can be positioned so that the surface on which the second external member is to be placed is parallel to the first external member. This allows the second external member, such as a rotor, to rotate horizontally relative to the first external member, such as a housing, thereby stabilizing the flight of the flying object or the movement of the object.

[0030] The cross-sectional shape of the extension portion 140, the cross-sectional shape of the lower surface, and the presence or absence of a flange can be determined from the viewpoint of resistance to torsional stress generated in the article equipped with the arm 100, and from the viewpoint of aerodynamic characteristics.

[0031] The tip portion 150 may have a flat upper surface for holding a second external member. The tip portion 150 and the extension portion 140 may be integrally molded or connected via a connecting portion. Multiple fastening holes 150a (four in Figure 1, though not limited to) are formed in the flat upper surface for fastening a second external member such as a rotor unit. An opening 150b is also formed in the upper surface of the tip portion 150 for routing wiring from the inside to the outside of the arm 100.

[0032] The cross-sectional shape of the tip portion 150, particularly the cross-sectional shape of the lower surface, and the presence or absence of a flange can be determined insofar as sufficient strength is obtained to hold a second external member such as a rotor unit.

[0033] Depending on the desired shape, mass, and productivity of the arm 100, the flange 120 can be positioned at the base 130, extension 140, and tip 150, as shown in Figures 1 and 3, or at any part (not shown) of the base 130, extension 140, and tip 150, or it can be omitted (not shown).

[0034] The overhang length of the flange 120 can be set considering the balance between the effect of improving rigidity and the aerodynamic changes caused by the flange 120. In one example, the flange located at the base portion 130 has a greater overhang length toward the outside of the main body portion 110 than the flanges located at the extension portion 140 and the tip portion 150, respectively. From the viewpoint of suppressing a decrease in the strength of the arm 100 and the durability of the fastening portion, it is preferable that the flange located at the base portion 130 has fastening holes 120a into which fastening screws for attaching the arm 100 to the first external member are inserted. The fastening holes 120a can be formed by nut members located one or more times on each of the flanges (120, 120), for example, at two locations, front and rear, as shown in Figure 1.

[0035] The arm may optionally have a cover (not shown) on its underside for protecting wiring, for example. The cover may be flat or semi-cylindrical with a bulge on the underside. The cover may be attached by forming an opening in the flange and inserting fastening screws into the opening, or by using adhesive.

[0036] <Fiber-reinforced resin layer> The fiber-reinforced resin layer is a resin-containing layer reinforced with fibers, and at least one layer is included in the arm.

[0037] The fiber-reinforced resin layer of this disclosure comprises reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated into the reinforcing fibers. The reinforcing fibers and matrix resin contained in the fiber-reinforced resin layer were discovered from the viewpoint of improving the vibration suppression of the arm, and consequently, the flight stability of the arm and the flying object equipped therewith can also be improved.

[0038] A fiber-reinforced resin layer, in the case of a single layer, contains a matrix resin and reinforcing fibers arranged in the same direction within the same layer. Therefore, a layer in which the reinforcing fibers are oriented in one direction and a layer in which the reinforcing fibers are oriented in different directions are considered separate reinforcing fiber layers. When a reinforcing fiber layer is manufactured by continuously laminating multiple layers such that the reinforcing fibers are oriented in the same direction, observing the cross-section of the laminate or the arm containing it reveals that the reinforcing fibers of the lower layer form a single cluster of reinforcing fibers, while the reinforcing fibers of the upper layer form clusters of different reinforcing fibers. Thus, even if layers in which the reinforcing fibers are oriented in the same direction are arranged continuously in the lamination direction, if they are formed as separate layers during manufacturing, and as a result, clusters of reinforcing fibers are observed separately in the cross-section (i.e., a region rich in matrix resin is observed between the upper and lower clusters of reinforcing fibers), these are considered separate reinforcing fiber layers.

[0039] In one embodiment, the arm has specified components, layer structure, and orientation angle of the reinforcing fibers in the fiber-reinforced resin layer. Specifically, the fiber-reinforced resin layer includes reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated in the reinforcing fibers, and the fiber-reinforced resin layer satisfies the following conditions I or II when the longitudinal direction of the arm is 0°: Condition I: Includes two or more selected from the group consisting of the following layers A to C; Condition II: Includes the following layer B; Layer A: A layer in which the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer is greater than -3° and less than +3°; Layer B: A layer in which the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer is between -35° and -3°, and / or between +3° and +35°; Layer C: A layer in which the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer is between -80° and less than -35°, and / or greater than +35° and +80°.

[0040] According to this disclosure, two conditions, Condition I and Condition II, were found in relation to the vibration suppression of the arm and the fiber orientation of the fiber-reinforced resin layer. Surprisingly, satisfying Condition I or Condition II as a fiber-reinforced resin layer makes it possible to control the fiber orientation of the fiber-reinforced resin layer constituting the arm to the extent that vibrations generated at any part of the arm, for example at the tip of the arm, are suppressed from being transmitted to the base of the arm or the first external member.

[0041] While we do not wish to be constrained by theory, it is presumed that satisfying condition I or condition II as at least one fiber-reinforced resin layer included in the arm will not only suppress vibration at any part of the arm, for example at the tip of the arm, by suppressing both the longitudinal deflection of the arm and the torsion about the longitudinal axis of the arm, but also prevent the resulting vibration from being transmitted to the base of the arm or the first external member.

[0042] Layer A is a fiber-reinforced resin layer in which the orientation angle of the reinforcing fibers is greater than -3° and less than +3° when the longitudinal direction of the arm is set to 0°, and is thought to be mainly effective in suppressing the deflection of the arm in the longitudinal direction. Layer A may be a single layer or a multi-layer layer. When the arm includes layer A, the total thickness of layer A along the thickness direction of the arm is preferably 25% or more of the total thickness of the fiber-reinforced resin layer, from the viewpoint of increasing the vibration suppression effect.

[0043] Layer B is a fiber-reinforced resin layer in which, when the longitudinal direction of the arm is defined as 0°, the orientation angle of the reinforcing fibers is from -35° to -3° inclusive and / or from +3° to +35° inclusive. This is considered to be effective not only for suppressing deflection in the longitudinal axis direction of the arm, but also for suppressing torsion about the longitudinal direction of the arm. Layer B may be a single layer or multiple layers.

[0044] Layer C is a fiber-reinforced resin layer in which, when the longitudinal direction of the arm is defined as 0°, the orientation angle of the reinforcing fibers is from -80° to less than -35° and / or more than +35° to +80° inclusive. This is considered to be mainly effective for suppressing torsion about the longitudinal direction of the arm. When the longitudinal direction of the arm is defined as 0°, it is preferable that the orientation angle of the reinforcing fibers is from -45° to less than -35° and / or more than +35° to +45° inclusive, because this increases the vibration suppression effect of the arm. Layer C may be a single layer or multiple layers.

[0045] Condition I, which includes two or more layers selected from the group consisting of layer A to layer C, can achieve both deflection suppression and torsion suppression, suppress vibration of the arm, and consequently improve the flight stability of the arm and a flying object including the arm.

[0046] When condition I is satisfied, from the viewpoint of increasing the vibration suppression effect of the arm, a laminate obtained by laminating two or more reinforcing fiber layers having different orientation angles of reinforcing fibers is preferable, and / or the arm preferably includes layer A and layer B.

[0047] Condition II, which includes layer B, can achieve both deflection suppression and torsion suppression, suppress vibration of the arm, and consequently improve the flight stability of the arm and a flying object including the arm. According to the present disclosure, as described above, layer B is considered to be effective for both deflection suppression and torsion suppression of the arm, so even when only condition II is satisfied, vibration of the arm can be suppressed.

[0048] When condition II is satisfied, the fiber-reinforced resin layer is preferably layer B. If the fiber-reinforced resin layer consists only of layer B, the types of layers constituting the arm can be reduced, and productivity can be improved.

[0049] When the arm comprises a layer A and a layer B, with the longitudinal direction of the arm defined as 0°, it is preferable that the orientation angles of the reinforcing fibers are -15° or more and -3° or less, and / or +3° or more and +15° or less, because this increases the vibration suppression effect of the arm.

[0050] When the arm comprises a layer A and a layer B, from the viewpoint of increasing the vibration suppression effect of the arm, it is preferable that the total thickness of the layer A and the layer B in the fiber-reinforced resin layer accounts for 25% or more in the thickness direction relative to the entire fiber-reinforced resin layer. Further, from the viewpoint of ease of lamination, it is preferable that the total thickness of the layer A is larger than the total thickness of the layer B, or when the thicknesses of the two layers are substantially equal, it is preferable that the total number of the layers A is larger than the total number of the layers B.

[0051] When the arm comprises a layer B, from the viewpoint of increasing the vibration suppression effect of the arm, it is preferable that the total thickness of the layer B in the fiber-reinforced resin layer accounts for 25% or more in the thickness direction relative to the entire fiber-reinforced resin layer.

[0052] When the arm comprises a layer A and / or a layer B, when the area outside the center in the thickness direction of the arm is divided into an outer region and a central region, it is preferable that the proportion of the layers A and B is larger in the outer region than in the central region. When the layers A and B are arranged more in the outer region than in the central region along the thickness direction of the arm, the vibration suppression effect tends to be enhanced. From the viewpoint of increasing the vibration suppression effect, when the area outside the center in the thickness direction of the arm is divided into an outer region and a central region, it is preferable that the proportion of the layer A is larger in the outer region than in the central region. Furthermore, when the area outside the center in the thickness direction of the arm is divided into an outer region and a central region, it is more preferable that the proportion of the layer A is larger in the outer region than in the central region, and the proportion of the layer C is larger in the central region than in the outer region. When the layer A is arranged more in the outer region than in the central region along the thickness direction of the arm, and the layer C is arranged more in the central region than in the outer region along the thickness direction of the arm, the vibration suppression effect tends to be further enhanced.

[0053] Referring to Figure 2, the following explains how to position the center, outer, or inner part of the arm along the thickness direction (z), divide the area outside the center of the arm into an outer region and a central region, calculate the ratio of layer A and layer B, and compare them for each region.

[0054] As shown in Figure 2(a) or Figure 2(b), the center of the arm along its thickness direction (z) can be identified by observing the cross-section at the center in the width direction (y) of the arm. The area outside the center along the thickness direction (z) of the arm in this cross-section is divided into an outer region and a central region, and the ratio of layer A and layer B in the outer region is compared with the ratio of layer A and layer B in the central region.

[0055] When the cross-section of the arm is formed into a shape with an open bottom, such as a semi-cylindrical, hat-shaped, bowl-shaped, U-shaped, or C-shaped form, the upper side (i.e., the outside) and the lower side (i.e., the inside) can be distinguished from the cross-sectional shape of the arm, using the center of the thickness of the arm along the thickness direction (z) of the arm in the cross-section at the center of the width direction (y) of the arm as a reference.

[0056] If the cross-section of the arm has a generally flat shape on the bottom surface, such as a block or plate shape, as shown in Figure 2(a), and it is difficult to distinguish between the inside and outside from the cross-sectional shape of the arm, then either direction can be considered the outside with respect to the center of the thickness of the arm along the thickness direction (z) of the arm in the cross-section at the center of the width direction (y) of the arm (if it is difficult to determine the thickness direction (z) of the arm, then the thickness direction of the fiber-reinforced resin layer).

[0057] When the arm includes a laminate of multiple fiber-reinforced resin layers, from the viewpoint of suppressing both longitudinal deflection of the arm and twisting along the longitudinal axis, it is preferable that the orientation angles of the reinforcing fibers of adjacent fiber-reinforced resin layers in the thickness direction differ, except for the center of the laminate of the fiber-reinforced resin layers. In this disclosure, the center of the laminate refers to the central position relative to the number of laminates (layers).

[0058] Specifically, when the total number of layers is odd, the center of the stack is the central layer, and it is preferable that all adjacent layers have different orientation angles. For example, if the number of layers is 15, the 8th layer can be the center of the stack, and even if the 8th layer is excluded, it is preferable that the 1st to 7th layers and / or the 9th to 15th layers have different orientation angles.

[0059] Specifically, when the total number of layers is even, the center of the layer is the overlapping position of regions where the number of layers (sheets) is half the total number. For example, if the number of layers is 16, the center of the layer is between the 8th and 9th layers, and it is preferable that the orientation angles of adjacent layers other than this overlapping position are different.

[0060] When an arm includes a laminate of multiple fiber-reinforced resin layers, it is preferable that the fiber-reinforced resin layers be symmetrically laminated, from the viewpoint of achieving both suppression of longitudinal deflection and suppression of twisting around the longitudinal axis of the arm, and from the viewpoint of improving vibration suppression. In this disclosure, symmetrical lamination refers to a state in which fiber-reinforced resin layers are laminated such that the orientation angle of the reinforcing fibers is plane-symmetrical in the lamination direction with respect to the center of the laminate.

[0061] Specifically, when the total number of symmetrical layers is odd, it is preferable that the orientation angle or order of the reinforcing fibers laminated as upper and lower layers is the same, using the surface where the thickness of the central layer of the lamination is half as a reference. When the total number of symmetrical layers is even, it is preferable that the orientation angle or order of the reinforcing fibers laminated as upper and lower layers is the same, using the interface between regions where the number of layers (sheets) in the central lamination is half the total number as a reference.

[0062] From the viewpoint of efficiently suppressing vibrations, the arm preferably does not include a fiber-reinforced resin layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -80°, and / or greater than +80° and less than or equal to +90°, when the longitudinal direction of the arm is set to 0°, more preferably does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -45°, and / or greater than +45° and less than or equal to +90°, and even more preferably does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -35°, and / or greater than +35° and less than or equal to +90°.

[0063] From the viewpoint of efficient vibration suppression, reduction of the number of layers, and productivity, the arm preferably comprises both layer A and layer B, or preferably layer B, regardless of the presence or absence of layer C, and, if desired, layer C can be omitted as long as condition I is satisfied.

[0064] When an arm includes a laminate of multiple fiber-reinforced resin layers, from the viewpoint of balancing the mechanical properties of the arm, it is preferable that, excluding layer A, the number of fiber-reinforced resin layers whose reinforcing fiber orientation angles are approximately symmetrical with respect to the longitudinal direction (0°) of the arm is the same. For example, if the laminate includes two fiber-reinforced resin layers with a reinforcing fiber orientation angle of -30°, it is preferable that the laminate also includes two fiber-reinforced resin layers with a reinforcing fiber orientation angle of 30°. Here, "approximately symmetrical" means symmetrical with respect to a tolerance of ±3°. For example, for a fiber-reinforced resin layer with a reinforcing fiber orientation angle of -30°, fiber-reinforced resin layers with reinforcing fiber orientation angles of 27° to 33° are approximately symmetrical with respect to the longitudinal direction (0°) of the arm.

[0065] The number of layers A, B, and C, and the total number of layers A through C, are not limited as long as condition I or condition II is met. From the viewpoint of reducing the weight of the arm, it is preferable to have a small number of reinforcing fiber layers constituting the laminate. On the other hand, from the viewpoint of increasing the rigidity or multi-functionality of the arm, it is preferable to have a large number of reinforcing fiber layers constituting the laminate.

[0066] The arm may optionally include, in addition to a fiber-reinforced resin layer comprising reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated into the reinforcing fibers, another fiber-reinforced resin layer that does not contain reinforcing fibers arranged in a unidirectional orientation, such as a random sheet layer or an injection-molded layer.

[0067] The fiber-reinforced resin layer may consist only of reinforcing fiber layers in which the reinforcing fibers do not form a woven or knitted fabric (hereinafter also simply referred to as "non-woven layers"), or it may have reinforcing fiber layers in which the reinforcing fibers form a woven or knitted fabric (hereinafter also simply referred to as "woven layers"). However, since non-woven layers have higher rigidity than woven layers, it is preferable for the fiber-reinforced resin layer to have more non-woven layers than woven layers, and more preferably to consist only of non-woven layers.

[0068] The fiber-reinforced resin layer may optionally contain components other than the reinforcing fibers and matrix resin, such as resins that do not impregnate the reinforcing fibers.

[0069] The fiber-reinforced resin layer is not limited to, but can be formed, for example, as a single-layer or multi-layer laminated sheet, a single-layer or multi-layer laminated tape, etc., from the viewpoint of satisfying the above conditions I or II. The components of the fiber-reinforced resin layer are described below.

[0070] • Reinforcement fibers: Reinforcement fibers are arranged in a unidirectional orientation. From the viewpoint of arm rigidity, continuous reinforcement fibers arranged continuously in a unidirectional direction are preferable.

[0071] The type of reinforcing fiber is not particularly limited, and carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and metal fiber can be used. Of these, carbon fiber and aramid fiber are preferred, especially from the viewpoint of reducing the weight of the arm and further increasing its specific stiffness, due to their low density. Carbon fiber, in particular, is less prone to delamination at the interface with the matrix resin, making it easier to increase the strength of the arm. In addition, carbon fiber is less prone to cracking when subjected to impact and easily absorbs stress, making it less likely for the arm to break.

[0072] From the viewpoint of sufficiently enhancing the effect of improving rigidity, the average diameter of the reinforcing fibers is preferably 1 μm to 20 μm, and more preferably 4 μm to 10 μm.

[0073] The length of the reinforcing fibers is usually 15 mm or more, preferably 20 mm or more, and more preferably 100 mm or more. It is preferable that each reinforcing fiber is arranged continuously from one end to the other end when the arm is viewed in plan. The length of each reinforcing fiber can be determined by the distance from the base to the tip of the arm at the position where the reinforcing fiber is arranged.

[0074] Furthermore, the reinforcing fibers may be sized using a sizing agent.

[0075] The sizing agent is not particularly limited, but modified polyolefins are preferred, and modified polyolefins containing metal carboxylate salts are more preferred. Modified polyolefins are, for example, obtained by grafting carboxylic acid groups, carboxylic acid anhydride groups, or carboxylic acid ester groups onto the polymer chain of an unmodified polyolefin, and forming salts between the functional groups and metal cations. These sizing agents may be derived from fossil fuels, biomass raw materials, or mixtures thereof.

[0076] The above unmodified polyolefin is preferably an ethylene-based polymer having a content of 50 mol% or more of constituent units derived from ethylene, or a propylene-based polymer having a content of 50 mol% or more of constituent units derived from propylene. Examples of the above ethylene-based polymer include ethylene homopolymers and copolymers of ethylene and α-olefins having 3 to 10 carbon atoms. Examples of the above propylene-based polymer include propylene homopolymers and copolymers of propylene and ethylene or α-olefins having 4 to 10 carbon atoms. The above unmodified polyolefin is preferably homopolypropylene, homopolyethylene, ethylene-propylene copolymer, propylene-1-butene copolymer, or ethylene-propylene-1-butene copolymer.

[0077] Furthermore, the reinforcing fibers may be bundled together to form fiber bundles. In this case, the number of single filaments per bundle of bundled carbon fibers is preferably 100 to 100,000, and more preferably 1,000 to 50,000.

[0078] The reinforcing fiber content relative to the total mass of the arm is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 75% by mass or less, even more preferably 30% by mass or more and 70% by mass or less, and particularly preferably 35% by mass or more and 70% by mass or less.

[0079] The reinforcing fiber content relative to the total volume of the arm is preferably 10% to 70% by volume, more preferably 15% to 60% by volume, and even more preferably 20% to 60% by volume.

[0080] In the matrix resin arm, the matrix resin impregnated with the reinforcing fibers can hold the reinforcing fibers. The matrix resin may be a thermoplastic resin or a thermosetting resin. The matrix resin may be a crystalline resin or an amorphous resin.

[0081] Examples of thermoplastic resins that constitute the matrix resin include polyolefin resins such as polyethylene, polypropylene, polybutene, and poly-4-methyl-1-pentene, polyamide resins, polyester resins, polystyrene resins, thermoplastic polyimide resins, polyamide-imide resins, polycarbonate resins, polyphenylene ether resins, polyphenylene sulfide resins, polyacetal resins, acrylic resins, polyetherimide resins, polysulfone resins, polyetherketone resins, polyetheretherketone resins, polyarylate resins, polyethernitrile resins, vinyl chloride resins, ABS resins, and fluororesins. These thermoplastic resins may be derived from fossil fuels, from biomass raw materials, or mixtures thereof.

[0082] Examples of thermosetting resins that constitute the matrix resin include epoxy resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, silicone resins, urethane resins, furan resins, ketone resins, xylene resins, thermosetting polyimide resins, unsaturated polyester resins, and diallyl terephthalate resins. These thermosetting resins may be derived from fossil fuels, from biomass raw materials, or mixtures thereof.

[0083] Of these, thermoplastic resin is preferred, and polyamide resin and polyolefin resin are more preferred, from the viewpoint of making the arm less susceptible to damage from flying objects such as pebbles. Furthermore, from the viewpoint of suppressing the decrease in mechanical properties when the arm absorbs water, polyolefin resin is more preferred, and polypropylene resin is even more preferred.

[0084] The matrix resin may be a resin composition containing additives. Examples of additives include known fillers (inorganic fillers, organic fillers), pigments, dyes, weather stabilizers, heat stabilizers, antistatic agents, anti-slip agents, antioxidants, antifungal agents, antibacterial agents, flame retardants, and softeners. For example, when the matrix resin is melted by laser irradiation to fuse each reinforcing fiber layer to one another, the matrix resin is preferably a resin composition containing a dye that absorbs laser light of the irradiated wavelength. The dye may be any dye that absorbs light of any wavelength between 300 nm and 3000 nm, and carbon black is preferred.

[0085] Furthermore, the matrix resin may also contain other resins or other components such as short fibers shorter in length than the carbon fibers.

[0086] The matrix resin content relative to the total mass of the arm is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 70% by mass or less, even more preferably 30% by mass or more and 70% by mass or less, and particularly preferably 30% by mass or more and 65% by mass or less.

[0087] The matrix resin content relative to the total volume of the arm is preferably 30% to 90% by volume, more preferably 40% to 85% by volume, and even more preferably 40% to 80% by volume.

[0088] <Manufacturing of the Arm> An example of the manufacturing of the arm related to this disclosure is as follows:

[0089] As described above, the fiber-reinforced resin layer may be formed as, for example, a single-layer or multi-layer laminated sheet, a single-layer or multi-layer laminated tape, etc., to satisfy condition I or condition II, or a laminate may be formed of a fiber-reinforced resin layer formed to satisfy condition I or condition II and another layer such as a random sheet layer or an injection-molded layer.

[0090] The arm can be manufactured by placing the fiber-reinforced resin layer or laminate, formed as described above, into a mold pre-shaped to the form of the arm, and then press molding, such as by a heated press.

[0091] If desired, the mold may have the shape of the flange as well as the main body of the arm pre-formed.

[0092] Manufacturing conditions such as mold temperature, pressure, internal surface smoothness, and pressing time can be set as known conditions, as long as the fiber-reinforced resin layer contained in the resulting arm satisfies condition I or condition II.

[0093] If necessary, the main body or flange of the arm removed from the mold can be post-processed, such as drilling holes for inserting a rotating shaft or installing a drive unit that rotates the rotor blades, connecting to a housing, or wiring; or attaching a cover to the underside of the arm.

[0094] <Flying Body> In another embodiment, a flying body is provided that includes the arm according to the above embodiment.

[0095] The flying object is not limited to any particular type, but it is preferably capable of flight and movement while flying. For example, it may have a drive mechanism, such as a motor that rotates a rotor, at the tip of an arm. The flying object may be manned or unmanned.

[0096] Examples of flying objects, though not limited to them, include drones, airplanes, flying cars, manned helicopters, radio-controlled unmanned helicopters, and kites. Among these, drones are preferred from the viewpoint of compatibility with the arm relating to this disclosure.

[0097] The drone may comprise, for example, a housing in which batteries and the like are housed, one or more rotors for flying the drone, and the aforementioned arms for holding the rotors outside the housing and at a distance from the housing.

[0098] The enclosure may be, for example, an outer casing, a box, a loading platform, a plate-shaped member, a base material, etc., and may optionally have a flat section or a storage section for installing an energy storage device, an electrical wiring board, a circuit board, an IC chip, etc.

[0099] Figure 4 is a schematic diagram showing the external appearance of a drone as an example of a flying object. The drone 400 has a housing 410, a rotor unit 420, and multiple arms 100 (four in Figure 4, though not limited to four).

[0100] As shown in Figure 4, the housing 410 may have a substantially square plane with curved sides that bulge outward. Mounting portions 410a for attaching the arm 100 are located at the four ends of the substantially square. The mounting portions 410a are box-shaped parts that protrude in the direction of extension of the arm 100, and on their outer side, an inlet (not shown) may be formed for guiding wiring from an electrochemical device such as a battery housed in the housing 410 to the arm 100. The arm 100 can be attached to the housing 410 via the mounting portions 410a.

[0101] The rotor units 420 are positioned at the ends of each of the four arms 100. Each rotor unit 420 has multiple rotors 420a (not limited to two rotors in Figure 4) and a drive unit 420b for rotating the rotors 420a. The drive unit 420b is, for example, a motor and is positioned at the end of the arm 100. Wiring from a battery located in the housing 410 is connected to the drive unit 420b. The drive unit 420b rotates the rotors 420a using the power supplied via the wiring.

[0102] The arm 100 holds the rotor unit 420 at its tip, creating a predetermined distance between the rotor 420a and the housing 410, and between the rotors 420a positioned on each arm 100. This allows the arm 100 to prevent or suppress collisions between the rotating rotor 420a and the housing 410, or between the rotating rotors 420a themselves. The arm 100 may also be bent or flexed in the middle. Furthermore, although the arm extends outward from the center of gravity of the housing in Figure 4, it may extend in a direction that has a predetermined angle with respect to the direction outward from the center of gravity of the housing.

[0103] The drone 400 may optionally be equipped with legs 430, which can improve shock absorption during takeoff and landing, handling, safety in the event of a collision with another object, and connectivity with further items.

[0104] The embodiments described above are examples of the present disclosure, and the present invention is not limited to the embodiments described above. Within the scope of the spirit of the present invention, it can be implemented in a variety of forms or methods for a variety of applications.

[0105] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the examples.

[0106] 1. Fabrication of the Arm A UD sheet (manufactured by Mitsui Chemicals, Inc., trade name TAFNEX®, fiber volume fraction (Vf) 50%, thickness 0.15 mm) was prepared as the fiber-reinforced resin layer, consisting of continuous carbon fibers oriented in one direction impregnated with a polypropylene matrix resin. Using a die-cutting machine, this UD sheet was punched out into the shape of the arm to produce a fiber-reinforced resin sheet. At this time, with the longitudinal direction of the arm as 0° and clockwise as the direction in which the angle increases, the fiber-reinforced resin sheet was fabricated so that the orientation angle of the reinforcing fibers was as shown in Table 1 or Table 2.

[0107] Each arm was fabricated by stacking the prepared fiber-reinforced resin sheets in the mold in the order shown in Table 1 or Table 2, and welding the sheets together by heating, cooling, and pressing. The heating and cooling press was performed with a mold temperature of 200°C, a pressure of 5 MPa, and a heating time of 2 min. After that, the mold was water-cooled while maintaining the pressure, and the mold was cooled and pressed until the mold temperature reached 65°C. The time it took for the mold temperature to reach 65°C was approximately 5 min to 10 min.

[0108] 2. Evaluation of the arm

[0109] 2-1. Evaluation Method An arm was attached to a fixing jig, a blade was attached to the vicinity of the arm tip via a motor, and an acceleration pickup was attached to the fixing jig near the base of the arm. Time-series data of vibration acceleration was acquired when the blade was rotated at a constant rotational speed. Fast Fourier Transform (FFT) was applied to the time-series data acquired by the acceleration pickup, and the amount obtained by integrating the amplitude of vibration acceleration in the range of 0 Hz to 500 Hz (hereinafter referred to as "quantity I") was compared for each level. Note that a smaller quantity I means that the vibration transmitted from the arm tip to the base of the arm is suppressed.

[0110] 2-2. Evaluation Results

[0111] 2-2-1. Experiment A: For each example of the 15-ply laminated sample, an arm was fabricated by stacking 15 fiber-reinforced resin sheets as shown in Table 1, and evaluated. The evaluation results are shown in Table 1. The thickness of layers A and B in the fiber-reinforced resin layer relative to the total thickness of the fiber-reinforced resin layer was defined as the "thickness ratio of layers A and B (%)".

[0112]

[0113] 2-2-2. Experiment B: For each example of the 16-ply laminated sample, an arm was fabricated by stacking 16 fiber-reinforced resin sheets as shown in Table 2, and evaluated. The evaluation results are shown in Table 2.

[0114]

[0115]

[0116] Tables 1 and 2 show the angles with the longitudinal direction of the arm as 0°, clockwise as the direction in which the angle increases (+), and counterclockwise as the direction in which the angle decreases (-).

[0117] As is clear from Tables 1 and 2, the arms (Examples 1-14) in which the fiber-reinforced resin layer satisfies either condition I or condition II described above had a small amount I and high vibration suppression. In particular, the arms containing layers A and B (Examples 1-3) had a remarkably small amount I and extremely high vibration suppression.

[0118] Furthermore, as shown in Examples 7 to 10 of Table 2, the arms (Examples 8 to 12) in which the fiber-reinforced resin layer satisfies either condition I or condition II above, and the thickness ratio (%) of layers A and B is 25% or more, showed remarkably low amount I and extremely high vibration suppression.

[0119] Furthermore, as shown in Examples 9 and 11 of Table 2, when the fiber-reinforced resin layer satisfies the above-mentioned condition I or condition II, and the arm is divided into an outer region and a central region from the center in the thickness direction, the arm in Example 11 where the ratio of layer A to layer B is larger in the outer region than in the central region had a significantly smaller amount I and very high vibration suppression.

[0120] Furthermore, as shown in Examples 11, 17, and 18 of Table 2, when the fiber-reinforced resin layer satisfies the above-mentioned condition I or condition II, and the arm is divided into an outer region and a central region from the center in the thickness direction, the arm (Example 11) in which the proportion of layer A is larger in the outer region than in the central region, and the proportion of layer C is larger in the central region than in the outer region, had a remarkably small amount I and very high vibration suppression performance.

[0121] Furthermore, as shown in Examples 9 and 12 of Table 2, in the arm (Example 12) where the fiber-reinforced resin layer satisfies either condition I or condition II above, and where the orientation angles of the reinforcing fibers between adjacent fiber-reinforced resin layers in the thickness direction differ, except for the center of the laminated fiber-reinforced resin layer, the amount I was significantly smaller and the vibration suppression was extremely high.

[0122] Furthermore, as shown in Examples 15-18 of Table 2, the arms in which the fiber-reinforced resin layer satisfies either condition I or condition II above, and the fiber-reinforced resin layer is layer B (Examples 15 and 16), showed a significantly smaller amount I and very high vibration suppression.

[0123] This application is a priority application claiming based on Japanese Patent Application No. 2025-052304, filed on 26 March 2025, and the claims, specification and drawings of said Japanese Patent Application are incorporated herein by reference.

[0124] 100 Arm 110 Main body 120 Flange 120a Fastening hole 130 Base 130a Base wall 130b Opening 140 Extension 150 Tip 150a Fastening hole 150b Opening 400 Drone 410 Housing 410a Mounting part 420 Rotor unit 420a Rotor 420b Drive unit 430 Foot x Longitudinal direction y Width direction (or lateral direction) z Vertical direction (or thickness direction or stacking direction)

Claims

1. An arm comprising at least one fiber-reinforced resin layer, wherein the fiber-reinforced resin layer comprises reinforcing fibers arranged in a unidirectional orientation and a matrix resin impregnated in the reinforcing fibers, and the fiber-reinforced resin layer satisfies either condition I or condition II below when the longitudinal direction of the arm is 0°: Condition I: comprises two or more layers selected from the group consisting of the following layers A to C; Condition II: comprises the following layer B; Layer A: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is greater than -3° and less than +3°; Layer B: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is between -35° and -3°, and / or between +3° and +35°; Layer C: a layer in which the orientation angle of the reinforcing fibers of the fiber-reinforced resin layer is between -80° and less than -35°, and / or greater than +35° and +80°; 2. The arm according to claim 1, wherein the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer of layer C is -45° or more and less than -35°, and / or greater than +35° and less than or equal to +45°.

3. The arm according to claim 1, comprising layer A and layer B.

4. The arm according to claim 3, wherein the orientation angle of the reinforcing fibers in the fiber-reinforced resin layer of layer B is -15° or more and -3° or less, and / or +3° or more and +15° or less.

5. The arm according to claim 1, wherein the thickness of layers A and B in the fiber-reinforced resin layer is 25% or more in the thickness direction relative to the entire fiber-reinforced resin layer.

6. The arm according to claim 1, wherein when the arm is divided into an outer region and a central region from the center in the thickness direction of the arm, the proportion of layer A and layer B is greater in the outer region than in the central region.

7. The arm according to claim 1, wherein, except for the center of the laminated fiber-reinforced resin layer, the orientation angles of the reinforcing fibers of adjacent fiber-reinforced resin layers in the thickness direction are different.

8. The arm according to claim 1, wherein the fiber-reinforced resin layer is symmetrically laminated.

9. The arm according to claim 1, wherein the fiber-reinforced resin layer does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -80°, and / or greater than +80° and less than or equal to +90°.

10. The arm according to claim 1, wherein the fiber-reinforced resin layer does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -45°, and / or greater than +45° and less than or equal to +90°.

11. The arm according to claim 1, wherein the fiber-reinforced resin layer does not include a layer in which the orientation angle of the reinforcing fibers is -90° or more and less than -35°, and / or greater than +35° and less than or equal to +90°.

12. The arm according to claim 1, wherein the fiber-reinforced resin layer is layer B.

13. The arm according to claim 1, wherein a drive unit for rotating a rotor blade is installed at the tip of the arm.

14. A flying body comprising the arm described in any one of claims 1 to 13.

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