Drone arm, drone, and method for manufacturing a drone arm

Abstract

To provide a drone arm or the like that has a small number of parts and can improve the efficiency of thrust generated by the rotation of the propeller. [Solution] The arm 1 is positioned where airflow is delivered by the rotation of the propeller and extends outward from the housing. The arm body 10 for securing a predetermined distance, the connecting part 20 for connecting to the housing, and the fixing part 30 for fixing the motor are integrally formed from carbon fiber reinforced thermoplastic. When the shape of the outer circumference of the cross-section of the arm body 10 in a direction perpendicular to the longitudinal direction of the arm body 10 is defined by the maximum height and the maximum width perpendicular to the maximum height, the maximum height is formed to be greater than the maximum width.

Description

Technical Field

[0001] The present invention relates to an arm for a drone, a drone, and a method for manufacturing an arm for a drone.

Background Art

[0002] A drone has a housing in which a flight control device and a battery are arranged, and a motor and a propeller for exerting thrust (for example, Patent Document 1). For example, in a drone with a relatively large maximum takeoff weight, such as a drone for agricultural chemical spraying, a propeller with a large diameter is adopted in order to secure a large thrust. And, in order to prevent interference between the housing and the propeller, the motor for rotating the propeller is arranged in the vicinity of the tip of an arm that extends outward from the housing. Conventionally, such an arm is generally formed of carbon fiber reinforced plastic (CFRP) from the viewpoints of weight and strength.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The arm 130 of the drone 100 shown in FIGS. 39, 40, and 41 is an example of the above-described arm. The arm 130 is a pipe made of CFRP. The arm 130 extends outward from the housing 110 from the four corners of the lower part of the housing 110 of the drone 100, the motor 122 is arranged in the vicinity of the tip of each arm 130, and the propeller 124 fixed to the rotation shaft 122a (see FIG. 42) of the motor 122 rotates, whereby the propeller 124 can obtain thrust without interfering with the housing 110.

[0005] Conventionally, a connecting member 140 was required to connect the arm 130 and the housing 110. As shown in Figures 40 and 41(a), the connecting member 140 has a notch 140a. As shown in Figure 41(b), when the end face 140b of the connecting member 140 is in contact with the peripheral portion 110a of the housing 110, as shown in Figure 41(c), the notch 140a engages with the component 110b that makes up the housing 110, thereby positioning and fixing the connecting member 140 relative to the housing 110.

[0006] Furthermore, a fixing member (motor mount) 120 is also required to secure the motor 122 near the tip of the arm 130. Therefore, in addition to the weight of the arm 130, the weight of the connecting member 140 and the fixing member 120 is added. Also, the number of parts increases, making the manufacturing process more complex. The connecting member 140 and the fixing member 120 are generally made of aluminum alloy.

[0007] When the propeller 124 rotates, a thrust F1 is generated, as shown in Figure 42(a). The thrust F1 is the force that lifts the drone 100 upward, as indicated by arrow Z1. On the other hand, when the propeller 124 rotates, a downward airflow Air1 is generated, as indicated by arrow Z2. When the airflow Air1 hits the arm 130 located below the propeller 124, a drag force dr1 is generated. The drag force dr1 is the resistance force of the arm 130 to the force acting on the arm 130 by the airflow Air1. The drag force dr1 becomes the force that pushes the drone 100 upward, as indicated by arrow Z2.

[0008] The rotation of the propeller 124 generates thrust F1 and drag dr1. As shown in Figure 42(b), thrust F1 is reduced by drag dr1, and the force that lifts the drone 100 upward becomes thrust F2. Thus, there is a problem that thrust F1 is reduced when the airflow Air1 hits the propeller 124. In this specification, the ratio of thrust F2 to thrust F1 (F2 / F1) is referred to as efficiency.

[0009] This invention attempts to solve the aforementioned problems and aims to provide a drone arm and drone that have fewer parts and can improve the efficiency of thrust generated by the rotation of the propeller. [Means for solving the problem]

[0010] The first invention relates to a drone that obtains thrust by the rotation of multiple propellers, and is a drone arm for arranging a housing that houses the drone's control device and battery and a motor for rotating the propellers at a predetermined distance, wherein the arm extends outward from the housing and is positioned where airflow generated by the rotation of the propellers connected to the motor's rotation axis flows, and the arm body is formed hollow, and the connecting part for connecting to the housing and the fixing part for fixing the motor are integrally formed from carbon fiber reinforced thermoplastic, and the arm body in a direction perpendicular to the longitudinal direction of the arm body The drone arm is characterized in that, when the shape of the outer circumference of the cross-section is defined by a maximum height and a maximum width perpendicular to the maximum height, the maximum height is formed to be greater than the maximum width, the outer circumference is formed symmetrically with respect to the center line of the line constituting the maximum height, the upper part of the outer circumference corresponding to the maximum height of the arm body is positioned to be closest to the rotation surface of the propeller, and the outer circumference is formed such that, compared to the case where the outer circumference of the cross-section of the arm body is circular, the amount to which the airflow generated by the rotation of the propeller reduces the thrust generated by the rotation of the propeller is reduced.

[0011] According to the configuration of the first invention, the drone arm is integrally formed from carbon fiber reinforced thermoplastic, with the arm body, a connecting part for connecting to the housing, and a fixing part for fixing the motor. The arm body, being made of carbon fiber reinforced thermoplastic, has high mechanical strength, and since the arm body, connecting part, and fixing part are integrally formed, separate connecting or fixing parts are not required. As a result, the number of parts is reduced, and the manufacturing process is simplified. Furthermore, the maximum height of the arm body is formed to be greater than the maximum width, and the upper part, which is the outer circumference corresponding to the maximum height, is positioned to be closest to the rotation surface of the propeller. This reduces the projected area with respect to the airflow from the propeller relatively. Furthermore, if the outer periphery of the cross-section of the arm body is asymmetrical with respect to the center line that constitutes the maximum height of the arm body, when the airflow generated by the rotation of the propeller hits the upper part of the arm body and then flows downward along both surfaces relative to the center line of the arm body (in the opposite direction to the plane of rotation of the propeller), the air pressure near one of the surfaces will differ from the air pressure near the other surface, resulting in a force perpendicular to the original thrust direction (hereinafter referred to as the "orthogonal force"). In this respect, according to the configuration of the first invention, the outer periphery is formed symmetrically with respect to the center line, so the above-mentioned orthogonal force does not occur. Moreover, the shape of the outer periphery is formed such that, compared to the case where the outer periphery of the cross-section of the arm is circular, the degree to which the airflow generated by the rotation of the propeller reduces the thrust generated by the rotation of the propeller is reduced.

[0012] The second invention is a drone arm that, in the configuration of the first invention, has the following characteristics: on the outer circumference, when the direction in which the center line extends is defined as the vertical direction, and the portion of the outer circumference opposite to the upper part is defined as the lower part, the width of the outer circumference, which is perpendicular to the vertical direction, is largest at the widest part, which is the portion with the maximum width, and decreases towards the upper part and further decreases towards the lower part.

[0013] According to the configuration of the second invention, the width of the outer circumference is largest at the widest point, decreases towards the top, and decreases towards the bottom. Therefore, when the airflow generated by the rotation of the propeller hits the top of the arm body, it flows smoothly downward, and the airflow flowing along the surface of the arm body smoothly separates from the bottom of the arm body.

[0014] The third invention is a drone arm in which, in the configuration of the second invention, the maximum width portion is formed at an intermediate position between the upper and lower parts in the vertical direction.

[0015] The inventors of the present invention have found a technical significance in that the efficiency described above differs depending on the position of the widest part. Specifically, when the widest part is closer to the bottom than to the top of the outer circumference, the efficiency is low. In this respect, according to the configuration of the third invention, the widest part is formed at an intermediate position between the top and bottom in the vertical direction, so the efficiency is relatively high.

[0016] The fourth invention is a drone arm in which, in the configuration of the second invention, the maximum width portion is formed closer to the upper part than to the lower part.

[0017] The inventors of this invention discovered that even greater efficiency can be achieved by forming the widest part closer to the top than to the bottom, and thus came up with a fourth invention.

[0018] The fifth invention is a drone arm in which, in the configuration of the second invention, the maximum width portion is formed at a position closer to the upper part than the intermediate position between the upper and lower parts.

[0019] The sixth invention is a drone arm in which, in the configuration of the second invention, the maximum width portion is formed at a position closer to an intermediate position between the upper and lower parts than the upper part.

[0020] The seventh invention is an arm for a drone, which in the configuration of the second invention, when considering the intermediate position between the upper part and the lower part, taking the distance from the upper part to the intermediate position as the first distance and the distance from the upper part to the maximum width part as the second distance, the ratio of the second distance to the first distance is 30 / 100 or more and 85 / 100 or less.

[0021] The inventor of the present invention found that if the maximum width part is too close to the upper part, the improvement in efficiency will be reduced, and thus came up with the seventh invention.

[0022] The eighth invention is an arm for a drone, which in the configuration of the fourth invention, the outer periphery has a smaller radius of curvature in the vicinity of the upper part including the upper part than that of the part other than the vicinity of the upper part.

[0023] According to the configuration of the eighth invention, the outer peripheral shape of the cross-section of the arm main body part has a shape called a so-called tear shape or a drop shape.

[0024] The ninth invention is an arm for a drone, which in the configuration of any one of the first to eighth inventions, the outer periphery does not include a straight line and is formed only by curves.

[0025] The inventor of the present invention found that when the outer peripheral shape of the cross-section of the arm main body part includes a straight line, the degree of increasing efficiency is smaller than that when it does not include a straight line. In this regard, according to the configuration of the ninth invention, since the outer periphery does not include a straight line and is formed only by curves, the degree of improving efficiency is large.

[0026] The tenth invention is an arm for a drone, which in the configuration of any one of the first to eighth inventions, when the airflow in the direction from the upper part to the lower part is flowed through the arm main body part, the difference between the pressure of the airflow in the vicinity of the upper part and the pressure of the airflow in the vicinity of the lower part is formed to be smaller than that when the outer periphery of the cross-section of the arm main body part is circular.

[0027] The eleventh invention is a drone arm in which, in the configuration of any one of the first to eighth inventions, ridges extending in a direction intersecting the longitudinal direction of the arm main body are formed over the entire arm main body on the inner surface of the arm main body.

[0028] According to the configuration of the eleventh invention, the shape of the arm main body is maintained by the ridges.

[0029] The twelfth invention is a drone having a drone arm according to any one of the first to eighth inventions.

[0030] The thirteenth invention is a method for manufacturing a drone arm for arranging a housing for storing a control device and a battery of the drone and a motor for rotating the propeller at a predetermined distance in a drone that obtains thrust by the rotation of a plurality of propellers. The drone arm is formed integrally of carbon fiber reinforced thermoplastic plastic with an arm main body formed hollow, a connection portion for connecting to the housing, and a fixing portion for fixing the motor. Two arm members having a shape divided into two along the longitudinal direction are connected to form the drone arm. The arm member is formed by placing a sheet made of carbon fiber reinforced thermoplastic plastic on a male mold and performing heat press molding in a state where the sheet is sandwiched between the male mold and a female mold.

[0031] According to the configuration of the thirteenth invention, even when the drone arm has a complicated shape, a lightweight and high mechanical strength drone arm can be manufactured using carbon fiber reinforced thermoplastic plastic.

Effects of the Invention

[0032] According to the present invention, the number of parts is small, and the efficiency of thrust by the rotation of the propeller can be improved.

Brief Description of the Drawings

[0033] [Figure 1] This is a schematic perspective view of a drone arm according to an embodiment of the present invention, viewed from the front. [Figure 2] This is a schematic perspective view of a drone arm, seen from above and behind. [Figure 3] This is a schematic plan view of a drone arm. [Figure 4] This is a schematic side view of a drone arm. [Figure 5] This is a schematic front view of a drone arm. [Figure 6] This is a schematic rear view of a drone arm. [Figure 7] This is a schematic cross-sectional view of a drone arm. [Figure 8] This is a schematic cross-sectional view of a drone arm. [Figure 9] This is a schematic cross-sectional view of a drone arm. [Figure 10] This is a diagram showing a schematic cross-section of a drone arm, viewed from the front. [Figure 11] This is a schematic plan view of the upper part of the drone arm. [Figure 12] This is a schematic perspective view of the upper part of the drone arm, seen from the front. [Figure 13] This is a schematic perspective view of the upper part of the drone arm, seen from the front. [Figure 14] This is a schematic perspective view of the upper part of the drone arm, seen from the rear. [Figure 15] This is a magnified view of the upper part of the drone arm. [Figure 16] This is a schematic diagram showing the connection between the upper and lower parts of the drone arm. [Figure 17] This is a schematic diagram showing the outer circumference of the cross-section of the main body of the arm used in preliminary testing. [Figure 18] This is a schematic diagram showing the results of a preliminary test. [Figure 19] This is a schematic diagram showing the testing method for the first test. [Figure 20]This is a schematic diagram showing a cross-section of the main body of the arm used in the first test. [Figure 21] This is a schematic diagram showing the results of the first test. [Figure 22] This is a schematic diagram showing the cross-section of the main body of the arm used in the second test. [Figure 23] This is a schematic diagram showing the results of the second test. [Figure 24] This is a schematic diagram showing the results of the second test. [Figure 25] This is a schematic diagram showing the testing method for the third test. [Figure 26] This is a schematic diagram showing the results of the third test. [Figure 27] This is a schematic diagram showing the results of the third test. [Figure 28] This is a schematic diagram showing the results of the third test. [Figure 29] This is a schematic diagram showing the results of the third test. [Figure 30] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 31] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 32] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 33] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 34] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 35] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 36] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 37] This is a schematic diagram showing a manufacturing method for a drone arm. [Figure 38] This is a schematic diagram showing the arm component removed from the mold. [Figure 39] This is a schematic diagram showing a conventional drone arm attached to a drone. [Figure 40] This is a schematic diagram showing an example of a conventional drone arm. [Figure 41] This is a schematic diagram showing an example of a conventional connection structure between a drone arm and its housing. [Figure 42] This is a schematic side view of a conventional drone, a conceptual diagram illustrating an example of thrust and drag generated by the rotation of the propellers. [Figure 43] This figure shows a drone equipped with the drone arm of this embodiment and a conventional drone equipped with a drone arm. [Modes for carrying out the invention]

[0034] The embodiments for carrying out the present invention will be described in detail below. In the following description, the same reference numerals will be used for similar components, and their descriptions will be omitted or simplified. Furthermore, descriptions of components that can be appropriately implemented by those skilled in the art will be omitted, and only the basic components of the present invention will be described.

[0035] <Structure of a drone arm> The drone arm 1 shown in Figures 1 to 6 (hereinafter referred to as "arm 1") is configured to be positioned between the housing and the motor in a drone that obtains thrust by the rotation of multiple propellers, ensuring a predetermined distance between them. The housing is configured to house the drone's control device and battery, and the motor is configured to rotate the propellers. The presence of arm 1 allows the propellers to rotate without interfering with the housing. In this embodiment, the direction indicated by arrow Y in Figure 1(a) is the longitudinal direction of arm 1, the direction indicated by arrow X is the width direction of arm 1, and the direction indicated by arrow Z is the height direction of arm 1 (also referred to as the "up and down direction"). The longitudinal direction, width direction, and height direction are orthogonal in relation to any two of these directions.

[0036] Arm 1 is connected to the housing 110 of the drone 100, for example, as a replacement for the conventional arm 130 in Figure 39. However, unlike arm 130, connecting member 140 and fixing member 120 are not required. Near one end of arm 1 is directly connected to the housing 110, and the motor 122 is directly fixed near the other end.

[0037] Figure 1(a) is a schematic perspective view of arm 1 viewed from above, and Figure 1(b) is a schematic perspective view of arm 1 viewed from below. Arm 1 is integrally formed from carbon fiber reinforced thermoplastic, comprising a hollow arm body 10, a connecting part 20 for connecting to the housing 110 (see Figure 39), and a fixing part 30 for fixing the motor 122.

[0038] Arm 1 is constructed by connecting an upper arm 1A and a lower arm 1B (see Figure 16). The upper arm 1A and the lower arm 1B are examples of arm members. In this embodiment, the upper arm 1A and the lower arm 1B have the same shape.

[0039] The upper part 20b1 (see Figure 1(a)) and lower part 20b2 (see Figure 1(b)) of the connecting part 20 are formed as flat surfaces. These flat surfaces are surfaces perpendicular to the vertical direction. A notch 20a (see Figure 1(a)) is formed in the connecting part 20. As shown in Figure 2(b), when the arm 1 is connected to the housing 110, the lower part 20b2 of the fixing part 20 comes into contact with the flat surface 110a of the housing 110. Then, as shown in Figure 2(c), the notch 20a engages with the fixing part 100b of the housing 110.

[0040] As shown in Figures 2(a) and 6, one end of the connection portion 20 is an opening 20s. The opening 20s allows power lines and signal lines to be placed between the housing 110 and the motor 122.

[0041] As shown in Figures 1(a) and 2(a), the fixing part 30 has a through hole 30s and screw holes 30a1, 30a2, 30a3, and 30a4. When the lower part of the motor 122 is fitted into the through hole 30s, the motor 122 is fixed to the fixing part 20 by the engagement of screws with both the screw holes (not shown) formed in the motor housing and the aforementioned screw holes 30a1, etc. The upper part 30b1 (see Figure 1(a)) and lower part 30b2 (see Figure 1(b)) of the fixing part 30 are formed as flat surfaces. These flat surfaces are surfaces perpendicular to the vertical direction.

[0042] Arm 1, like the conventional arm 130, extends outward from the housing 110 (see Figure 39) and is configured to be positioned where the airflow generated by the rotation of the propeller 124 flows (see Figure 39). Specifically, Arm 1 is positioned below the rotation plane of the propeller 124. Therefore, during the flight of the drone 1, the airflow generated by the rotation of the propeller 124 (hereinafter referred to as "propeller airflow") strikes Arm 1. Arm 1 of this embodiment is characterized by the fact that, due to the unique outer peripheral shape of its cross-section, the degree to which the propeller airflow strikes Arm 1, passes over and near the surface of Arm 1, and separates from Arm 1 is reduced compared to the conventional arm 130 (see Figures 39 and 40), resulting in improved efficiency.

[0043] <Outer circumference shape of the cross-section of arm 1> Figures 7 to 10 show the cross-section 10c of the arm body 10 in a direction perpendicular to the longitudinal direction of the arm body 10 (arrow Y direction shown in Figures 1 to 3). The cross-section 10c is defined by the outer circumference 10a and the inner circumference 10b.

[0044] When the shape of the outer perimeter 10a is defined by a maximum height h10 (see Figure 10) and a maximum width w10 (same), the maximum height h10 is formed to be larger than the maximum width w10. The direction of the maximum height h10 is the height direction indicated by arrow Z, and the direction of the maximum width w10 is the width direction indicated by arrow X.

[0045] The portion of the outer circumference 10a corresponding to the maximum height h10 is called the upper part 10a1. The end of the outer circumference 10a opposite to the upper part 10a1 is called the lower part 10a2. The direction connecting the upper part 10a1 and the lower part 10a2 (indicated by arrow Z) is the vertical direction. The upper vicinity including the upper part 10a1 and the lower vicinity including the lower part 10a2 are formed in a convex shape toward the outside. The portion of the outer circumference 10a corresponding to the maximum width w10 is called the maximum width portion 10a3.

[0046] In Figure 10, the dotted line XC1 is a line segment in the width direction, indicating the midpoint between the upper part 10a1 and the lower part 10a2. On the outer circumference 10a, the widest part 10a3 is formed in the portion corresponding to the dotted line XC1. That is, on the outer circumference 10a, the widest part 10a3 is formed at a position midway between the upper part 10a1 and the lower part 10a2.

[0047] The width of the outer circumference 10a is largest at the widest part 10a3 and decreases towards the upper part 10a1. Note that the widest part 10a3 is not configured to coincide with the upper part 10a1.

[0048] Furthermore, the width of the outer circumference 10a is largest at the widest part 10a3 and decreases towards the lower part 10a2.

[0049] As shown in Figure 10, if the line corresponding to the maximum height h10 is the center line ZC1, then the outer perimeter 10a is formed symmetrically with respect to the center line ZC1. If one half of the outer perimeter 10a is called outer perimeter 10aa and the other half is called outer perimeter 10ab, then outer perimeters 10aa and 10ab are formed symmetrically with respect to the line.

[0050] Furthermore, the outer perimeter 10a is formed symmetrically with respect to the aforementioned center line XC1. That is, the outer perimeter 10a is formed symmetrically in both the vertical and width directions.

[0051] In this embodiment, the outer circumference 10a is formed only by curves and does not include straight lines. Specifically, the outer circumference 10a is elliptical in shape.

[0052] As shown in Figure 10, the arm 1 is configured such that when it is fixed to the housing 110, the upper part 10a1 is positioned closest to the plane of rotation of the propeller 124. As described above, when the arm 1 is connected to the housing 110, the lower part 20b2 of the fixing part 20 abuts against the flat surface 110a of the housing 110, and since the lower part 20b is a surface perpendicular to the vertical direction, the upper part 10a1 is positioned at the highest position on the arm body 10, that is, the position closest to the plane of rotation of the propeller 124.

[0053] The aforementioned shape of the outer circumference 10a is designed to improve efficiency by reducing the degree to which the airflow generated by the rotation of the propeller 124 reduces the thrust generated by the rotation of the propeller 124 when it hits the main body 10 of the arm, compared to the case of a circular shape.

[0054] <Regarding upper arm 1A and lower arm 1B> The upper arm 1A and lower arm 1B will be described with reference to Figures 11 to 16. The upper arm 1A and lower arm 1B are examples of arm members. Figures 11 to 15 are schematic diagrams of the upper arm 1A viewed from the inner side. In this embodiment, the lower arm 1B has the same shape as the upper arm 1A, so its description is omitted.

[0055] Arm 1A has an arm body portion 10p, a connecting portion 20p, and a fixing portion 30p integrally formed. When arm 1A and arm 1B are connected, the arm body portions 10p of arm 1A and arm 1B constitute the arm body portion 10 of arm 1, the connecting portion 20p of arm 1A and arm 1B constitute the connecting portion 20 of arm 1, and the fixing portions 30p of arm 1A and arm 1B constitute the fixing portion 30 of arm 1.

[0056] On the inner surface of the arm body portion 10p, protrusions 12a and 12b are formed along the entire length of the arm body portion 10p, extending in a direction intersecting the longitudinal direction of the arm body portion 10p. The protrusions 12a and 12b are formed from the lowest part 10p2 (see Figures 11(a), 13, and 14) on the inner surface of the arm body portion 10p to the highest parts 10p1 (see Figures 12, 13, and 14), which are the ends in the width direction. As a result, on the inner surface of the arm body portion 10 of the arm 1, protrusions 12a and 12b extending in a direction intersecting the longitudinal direction of the arm body portion 10 are formed along the entire length of the arm body portion 10.

[0057] Figure 11(a) is a schematic plan view of arm 1A. Figure 11(b) is a schematic enlarged view of a portion of Figure 11(a), conceptually illustrating the relationship between the projections 12a and 12b and the arm body 10p. As shown in Figure 11(b), projection 12a forms an angle θ1 with respect to the arm body 10p, and projection 12b forms an angle θ2 with respect to the arm body 10p. The sum of angles θ1 and θ2 is 180 degrees. For example, angle θ1 is 30 degrees and angle θ2 is 150 degrees. Projections 12a and 12b intersect, forming an intersection point 12p.

[0058] As shown in Figure 15, the highest point 10p1 of the arm body 10p has alternating protrusions 14a and recesses 14b. The protrusions 14a and recesses 14b are located on the inside of the highest point 10p1 of the arm body 10p and are formed at the intersection point 12p of the ridges 12a and 12b.

[0059] As shown in Figure 16, arm 1 is formed by connecting arm 1A and arm 1B in a manner in which their inner surfaces face each other. At this time, the protruding portion 14a of arm 1A fits into the recessed portion 14b of arm 1B, and with the protruding portion 14a of arm 1B fitting into the recessed portion 14b of arm 1A, arm 1A and arm 1B are bonded together, and arm 1A and arm 1B become one unit, forming arm 1. The bonding method is, for example, room temperature plasma treatment, but is not limited to this.

[0060] <Dimensions of drone arm> Referring to Figure 3, in arm 1, for example, the length L10 of the arm body 10 is 140 millimeters (mm), the length L20 of the connecting part 20 is 60 millimeters (mm), and the length L30 of the fixing part 30 is 90 millimeters (mm). Furthermore, the width w10 of the arm body 10 is 15 millimeters (mm), the width w20 of the connecting part 20 is 46 millimeters (mm), and the width w30 of the fixing part 30 is 30 millimeters (mm). Also, referring to Figure 4, the height h10 of the arm body 10 is 30 millimeters (mm).

[0061] Focusing on the arm body 10, its width w10 is 15 millimeters (mm) and its height h10 is 30 millimeters (mm). Thus, the height h10 is larger than the width w10. In contrast, in the conventional pipe-shaped arm body 130 (see Figure 40), the outer shape of the cross-section was circular, and its diameter was approximately 20 millimeters (mm). By making the width w10 of the arm body 10 smaller than the diameter of the conventional arm body 130, the projected area with respect to the airflow from the propeller 124 (see Figures 10 and 39) is reduced, allowing the airflow to flow smoothly downwards.

[0062] Furthermore, by making the outer circumferential shape of the cross-section of the arm body 10 elliptical as described above, the airflow from the propeller 124 (see Figures 10 and 39) contacts the arm body 10, flows while contacting the surface of the arm body 10, and further reduces the degree to which it reduces the thrust due to the rotation of the propeller 124 when it separates from the arm body 10, compared to the conventional arm body 130.

[0063] Furthermore, by making the outer circumferential shape of the cross-section of the arm body 10 symmetrical both vertically (arrow Z direction) and horizontally (arrow X direction), and by connecting arms 1A and 1B of the same shape to form arm 1, the mechanical strength is improved to withstand external forces during the flight of the drone 100, while also significantly reducing the number of parts.

[0064] <Preliminary Examination> Figure 17 is a schematic diagram showing the outer circumferential shape of the cross-section of the arm body used in a preliminary test regarding the relationship between the outer circumferential shape of the cross-section of the arm body of the drone arm and the drag force dr1.

[0065] The following arm body parts were used: No. 1 (arm body part 10C), No. 2 (arm body part 10: the embodiment described above), No. 3 (arm body part 10F), No. 4 (arm body part 10E), and No. 5 (arm body part 10D). Arm body part No. 1 (arm body part 10C), etc., are collectively referred to as "samples".

[0066] No. 1 (arm body 10C) is a conventional arm and is not an embodiment of the present invention. In contrast, No. 2 (arm body 10: the embodiment described above), No. 3 (arm body 10F), No. 4 (arm body 10E), and No. 5 (arm body 10D) are embodiments of the present invention. No. 2 (arm body 10: the embodiment described above), No. 3 (arm body 10F), No. 4 (arm body 10E), and No. 5 (arm body 10D) are formed such that when an airflow is directed from top to bottom through each arm body, the difference between the pressure (atmospheric pressure) near the top of each arm body and the pressure (atmospheric pressure) near the bottom is smaller compared to the case of No. 1 (arm body 10C).

[0067] As shown in Figure 17, the outer circumferential shape of the cross-section of No. 1 (arm body part 10C) is circular, and the diameter w30 is 22 millimeters (mm). In other words, the diameter is 22 millimeters (mm).

[0068] The maximum width w10 of No. 2 (arm body 10) is 15 millimeters (mm), and the maximum height h10 is 30 millimeters (mm). The widest part is formed at the intermediate position (corresponding to the center line XC1).

[0069] The maximum width w10F of No.3 (arm body 10F) is 14.8 millimeters (mm), and the maximum height h10F is 42 millimeters (mm). The maximum width section 10Fa3 is formed closer to the upper part 10Fa1 than the lower part 10Fa2. Furthermore, the maximum width section 10Fa3 is formed closer to the intermediate position (the position corresponding to the center line XC1) than the upper part 10Fa1.

[0070] In No. 3 (arm body 10F), if the distance from the upper part 10Fa1 to the intermediate position on the center line ZC1 is denoted as distance j10F, and the distance from the upper part 10Fa1 to the widest part 10Fa3 is denoted as distance m10F, then the ratio of distance m10F to distance j10F (m10F / j10F) is approximately 66 / 100. Distance j10F is an example of the first distance, and distance m10F is an example of the second distance.

[0071] In No. 3 (arm body 10F), the radius of curvature in the upper vicinity, including the upper part 10Fa1, is smaller than the radius of curvature in the parts other than the upper vicinity (excluding the lower end vicinity).

[0072] The maximum width w10E of No. 4 (arm body 10E) is 11.5 mm, and the maximum height h10E is 42 mm. The maximum width w10E of arm body 10D is 11.3 mm, and the maximum height h10E is 42 mm.

[0073] The widest part 10Ea3 is formed closer to the upper part 10Ea1 than to the lower part 10Ea2. If the distance from the upper part 10Ea1 to the intermediate position on the center line ZC1 is distance j10E, and the distance from the upper part 10Ea1 to the widest part 10Ea3 is distance m10E, then the ratio of distance m10E to distance j10E (m10E / j10E) is approximately 50 / 100. Distance j10E is an example of the first distance, and distance m10E is an example of the second distance.

[0074] The radius of curvature in the upper vicinity, including the upper part 10Ea1, is smaller than the radius of curvature in the parts other than the upper vicinity (excluding the vicinity of the lower end).

[0075] The maximum width w10D of No. 5 (arm body 10D) is 11.3 millimeters (mm), and the maximum height h10D is 42 millimeters (mm). The widest part is formed at the intermediate position (corresponding to the center line XC1).

[0076] Unlike the sample shown in Figure 17, an embodiment of the present invention is also one in which the widest part is formed closer to the top than the midpoint between the top and bottom. Furthermore, an embodiment of the present invention is one in which the ratio of the second distance to the first distance (second distance / first distance) is between 20 / 100 and 85 / 100. Preferably, the ratio of the second distance to the first distance is between 20 / 100 and 85 / 100, more preferably between 30 / 100 and 85 / 100, more preferably between 30 / 100 and 70 / 100, and more preferably between 30 / 100 and 60 / 100.

[0077] As shown by arrow A1, an airflow of 9.8 meters per second (m / s) and 30 millimeters wide (mm) was applied to each sample from above, and the drag force dr1 of each sample was measured. Each sample was suspended from a balance scale in a manner in which the top of each sample faced upward and the longitudinal direction remained horizontal, and the drag force when subjected to the airflow was measured.

[0078] Basically, if the outer perimeter of the cross-section has the same shape, the drag force dr1 is proportional to the size of the projected area with respect to the airflow direction. Also, if the projected area is the same, the drag force dr1 depends on the shape of the outer perimeter of the cross-section. Therefore, in order to minimize the drag force dr1, it is necessary to minimize the projected area and then adopt the outer perimeter shape that minimizes the drag force dr1.

[0079] In this test, the maximum width of each sample can be considered to be the projected area of ​​each sample relative to the airflow A1. As shown in Figure 18, the drag force dr1 is largest for No. 1 (arm body 10C), and decreases in the order of No. 2 (arm body 10), No. 3 (arm body 10F), No. 5 (arm body 10D), and No. 4 (arm body 10E).

[0080] It is natural that the larger the projected area with respect to the airflow, i.e., the maximum width, the greater the drag force dr1 tends to be. The present invention is a technical concept for forming a cross-sectional outer shape that reduces the drag force dr1, even if the maximum width of the outer shape of the cross section is the same. Therefore, excluding the specific maximum width, in order to examine the influence of the elements of the outer shape of the cross section (hereinafter referred to as "drag elements") on the drag force dr1, we adopt the value obtained by dividing each drag force dr1 by the maximum width of each sample (gf / width) as a reference value gfref. The reference value gfref for each sample is 0.30 for No. 1 (arm body part 10C), 0.18 for No. 2 (arm body part 10), 0.08 for No. 3 (arm body part 10F), 0.09 for No. 5 (arm body part 10D), and 0.08 for No. 4 (arm body part 10E).

[0081] Here, let distance j be the distance from the widest part to the bottom. As one of the drag elements, we adopt the ratio k (j / w) of distance j to the maximum width w. The ratio k for No. 1 (arm body 10C) is 0.5, which is clearly smaller than the ratio k of the other samples. And the reference value gfref for No. 1 (arm body 10C) is clearly larger than that of the other samples. And the ratio k for No. 4 (arm body 10E) is 2.74, which is the highest value among the samples. And the reference value gfref for No. 4 (arm body 10E) is the smallest among the samples. From the above, it can be said that the larger the ratio k, the smaller the reference value gfref tends to be.

[0082] Both No. 2 (arm body 10) and No. 5 (arm body 10D) have their widest point at the center in the vertical direction, and are essentially elliptical in shape. However, No. 5 (arm body 10D) has a larger ratio of major axis to minor axis than No. 2 (arm body 10), resulting in a more elongated shape and a larger ratio k. Furthermore, the reference value gfref is smaller for No. 5 (arm body 10D) than for No. 2 (arm body 10). From this, it can be said that the larger the ratio k, the smaller the drag force dr1 tends to be.

[0083] Comparing No. 3 (arm body 10F) and No. 5 (arm body 10D), the ratio k is larger for No. 3 (arm body 10F), and the reference value gfref is also smaller for No. 3 (arm body 10F). The drag force dr1 is smaller for No. 5 (arm body 10D), which is thought to be due to the fact that the maximum width w of No. 5 (arm body 10D) is smaller than that of No. 3 (arm body 10F). Considering the reference value gfref, if the maximum width w of No. 5 (arm body 10D) were the same as that of No. 3 (arm body 10F) in a similar shape, it is expected that the drag force dr1 will also be smaller for No. 3 (arm body 10F). From this, it can be said that the larger the ratio k, the smaller the drag force dr1 tends to be.

[0084] Comparing No. 4 (arm body 10E) and No. 5 (arm body 10D), while the maximum width w and maximum height h are almost identical, there is a difference of more than 10% in both the drag force dr1 and the reference value gfref. Despite No. 4 (arm body 10E) having a slightly larger maximum width w, the drag force dr1 and the reference value gfref are smaller. From this, it can be said that the ratio k influences the drag force dr1. In other words, if the maximum width w and maximum height h are the same, it can be expected that the drag force dr1 tends to be smaller the closer the part corresponding to the maximum width w is to the top in the vertical direction.

[0085] Comparing No. 3 (arm body 10F) and No. 4 (arm body 10E), the maximum width of both is biased upwards above the midpoint in the vertical direction, but the degree of upward bias differs. However, the reference value gfref is substantially the same. From another perspective, No. 3 (arm body 10F) has a maximum width w 1.29 times that of No. 4 (arm body 10E), and the resistance force dr1 is 1.28 times, so the difference in maximum width w is roughly proportional to the difference in resistance force dr1. In that case, when the maximum width is biased upwards above the midpoint in the vertical direction, it cannot be said that the reference value gfref becomes smaller as the ratio k increases.

[0086] From the above, it can be seen that the larger the ratio k, the smaller the reference value gfref tends to be. However, if the maximum width is biased towards the upper part of the vertical axis compared to the middle part, the degree of this bias is expected to have little effect on the ratio k and the reference value gfref.

[0087] <Test 1> Figure 19 shows an example of a test method for measuring the relationship between the outer circumferential shape of the cross-section of a drone arm and thrust. As shown in Figure 19, a pressure sensor 202 is placed on a measuring stand 200. A propeller 208 is connected to the rotation axis 206 of a motor 204, and the motor 204 is positioned on the pressure sensor 202. The arm body 10X is positioned in a location where airflow from the rotation of the propeller 208 flows, in an embodiment in which its upper part is closest to the rotation plane of the propeller 208.

[0088] A 6-axis force sensor manufactured by Leptrino Co., Ltd. (headquarters: Saku City, Nagano Prefecture) was used as the pressure sensor 202. The model number of the 6-axis force sensor is DTI080501200A02. A 26-inch (660.04 mm) propeller manufactured by T-motor was used as the propeller 208. A T-motor U8lite L KV110 was used as the motor 204, and the rotation speed of motor 204 was set to 3000 revolutions per minute (rpm).

[0089] As the arm body portion 10X, the arm body portion 10A (Figure 20(a)), arm body portion 10B (Figure 20(b)), and arm body portion 10C (Figure 20(c)) shown in Figure 20 were used. Figures 20(a) to 20(c) show cross-sections of each arm body portion 10A to 10C in a direction perpendicular to the longitudinal direction. The arm body portions 10A and 10B were positioned so that their upper parts 10Aa1 and 10Ba1 were closest to the rotation plane of the propeller 208. The projected area, i.e., width w10, of the arm body portions 10A, 10B, and 10C with respect to the rotation plane of the propeller 208 was the same. Arm body portion 10A is an embodiment of the present invention, but arm body portions 10B and 10C are not embodiments of the present invention.

[0090] The arm body portion 10A has an elliptical outer cross-section and corresponds to the arm body portion 10 of the first embodiment. The arm body portion 10B is curved near the upper part 10Ba1, the central part 10Ba2, and the lower part 10Ba5, but the section between the upper part 10Ba1 and the central part 10Ba2, and the section between the central part 10Ba2 and the lower part 10Ba5 are straight lines. The arm body portion 10C has a circular outer cross-section and corresponds to the conventional arm body portion 130 (see Figure 40).

[0091] Figure 21 shows the results of Test 1. In the test apparatus of Figure 19, the thrust when the arm body 10X is not placed is defined as thrust F1, and the thrust when the arm body 10A etc. is placed is defined as thrust F2. The ratio of thrust F2 to thrust F1 (F2 / F1) is defined as efficiency (%). The efficiency when the arm body 10X is not placed is 100 percent (%). The efficiency was 97.9 percent for arm body 10A, 93.9 percent for arm body 10B, and 91.19 percent for arm body 10C.

[0092] The results of Test 1 showed that while the presence of the arm body reduces efficiency, efficiency is higher when the cross-section of the arm body is elliptical compared to when it includes straight lines or is circular. In other words, for the same maximum width, efficiency is higher when the cross-section of the arm body is elliptical compared to when it includes straight lines or is circular.

[0093] The results of Test 1 are consistent with the results of the preliminary test described above.

[0094] <Exam 2> Using the arm bodies 10D and 10E shown in Figures 22(a) and 22(b), and the arm body 10C with a circular cross-section, the change in atmospheric pressure over time near the arm bodies 10D, 10E, etc., when airflow was directed from above (in the direction indicated by arrow Z1 in Figures 22 and 23) was measured (calculated) using software. The pressure was measured in the range of -1000 Pa (-1.0000E+03) to 500 Pa (5.0000E+02).

[0095] The arm body portion 10D shown in Figure 22(a) has a substantially elliptical outer circumference 10Da, similar to the arm body portion 10A described above, but the ratio of height to width is larger than that of the arm body portion 10A. That is, the ratio of height to width (h10D / w10D) in the arm body portion 10D is larger than the ratio of height to width (h10 / w10) in the arm body portion 10A.

[0096] In the arm body portion 10E shown in Figure 22(b), the portion with the maximum width on the outer circumference 10Ea of the cross-section is formed in a position closer to the upper Ea1 than to the lower Ea2 in the vertical direction. That is, the portion with the maximum width is formed not in the portion corresponding to the straight line XC1 which indicates an intermediate position between the upper 10Ea1 and the lower 10Ea2, but in the portion corresponding to the straight line XC2E which indicates a position closer to the upper Ea1 than to the lower 10Ea2. The outer circumference shape of the cross-section of the arm body portion 10E is called a "teardrop shape".

[0097] Furthermore, the radius of curvature of the outer circumference 10Ea in the upper vicinity, including the upper part 10Ea1, is smaller than the radius of curvature of the parts other than the upper vicinity (excluding the lower vicinity). However, the outer circumference 10Ea does not contain any straight lines and is formed only of curves.

[0098] Test 2 yielded the pressure changes shown in Figures 23 and 24. In the still image of Figure 23, the difference between the arm body 10D and the arm body 10E is not clear, but when examined in the actual video, it is observed that the pressure at the lower part 10Da2 of the arm body 10D is significantly lower than the pressure at the lower part 10Ea2 of the arm body 10E for many periods, and the pressure difference between the upper part 10Da1 and the lower part 10Da2 of the arm body 10D is greater than the pressure difference between the upper part 10Ea1 and the lower part 10Ea2 of the arm body 10E for many periods. Therefore, the negative impact on thrust is smaller in the arm body 10E.

[0099] Figure 24 shows a comparison between the arm body 10D and the arm body 10C. In Figure 24(b), a region P1 with significantly lower pressure is present near the lower part of the arm body 10C compared to the upper part, and the pressure difference between the upper and lower parts is also substantial. Therefore, the negative impact of the arm body 10C on thrust is smaller in the arm body 10D.

[0100] Test 2 revealed that the teardrop-shaped outer cross-section of the arm body resulted in the smallest reduction in thrust, followed by the elliptical-shaped arm body.

[0101] The results of Test 1 are consistent with the results of the preliminary test described above.

[0102] <Exam 3> Using the arm bodies 10D and 10E shown in Figures 22(a) and (b), the change in air pressure (static pressure) over time at multiple locations near the arm bodies 10D and 10E was simulated and measured (calculated) when airflow was directed from above (in the direction indicated by arrow Z1 in Figure 22). The pressure was measured in the range from -1000 Pa (-1.0000E+03) to 500 Pa (5.0000E+02). However, in Figures 26 to 29, the range from -350 Pa (-3.50E+02) to 350 Pa (3.50E+02), which includes the measured values, is shown.

[0103] Figure 25 shows positions P0 to P3 as multiple locations where pressure was measured. Position P0 is at the top of the arm body 10D, and position P1 is at the bottom. Position P2 is slightly away from the bottom, and position P3 is even further away from the bottom. The measurement positions in the arm body 10E are the same as those in the arm body 10D.

[0104] As shown in Figure 26, at position P0, the pressure remains almost constant regardless of the passage of time, and the pressure is lower in the arm body 10D than in the arm body 10E. This is presumed to be because the shape of the upper part of the arm body 10D is more pointed than the shape of the upper part of the arm body 10E, resulting in a lower air density at position P0.

[0105] In Figure 27, the overall pressure in the arm body 10E is greater than that in the arm body 10D. However, focusing on the pressure difference between the pressure at position P0 in Figure 16 and the pressure at position P1 in Figure 17, the overall pressure difference in the arm body 10E is smaller. Furthermore, as time progresses, the pressure change in the arm body 10E becomes smaller and more stable than that in the arm body 10D.

[0106] As shown in Figure 28, at position P2, there is no significant difference in pressure between the arm body 10E and the arm body 10D even as time passes.

[0107] As shown in Figure 29, at position P3, there is no significant difference in pressure between the arm body 10E and the arm body 10D over time.

[0108] The positions that have the greatest impact on thrust reduction are the upper position P0 and the lower position P1 of the arm body. From the results of Test 3, when examining the pressure difference between the upper position P0 and the lower position P1 of the arm body, the pressure difference is smaller at the arm body 10E than at the arm body 10D and stabilizes over time. Therefore, the impact on thrust reduction is smaller at the arm body 10E than at the arm body 10D.

[0109] <Effects of attaching a drone arm to a drone> Figure 43(a) shows a drone 100A equipped with arm 1 according to an embodiment of the present invention. Figure 43(b) shows a conventional drone 100 equipped with arm 130. Drones 100A and 100 have basically the same configuration, but differ in that drone 100A is equipped with arm 1, while drone 100 is equipped with arm 130, connecting part 140 and fixing part 120. As a result, drone 100A is approximately 177 grams (g) lighter than drone 100.

[0110] A comparative flight test was conducted using Drone 100A and Drone 100. Two pilots operated both Drone 100A and Drone 100 manually. As a result, both pilots recognized that Drone 100A responded more quickly to commands such as changes in flight speed and direction compared to Drone 100, indicating improved maneuverability.

[0111] The reason for the improved maneuverability is clearly that the drone 100A is more efficient than the drone 100. Furthermore, while the drone 100 has an aluminum alloy fixing member 120 near the tip of the arm 130, the drone 100A has a fixing part 30 that is integrally formed with the arm body 10. Therefore, it is thought that the drone 100A has improved maneuverability because the part of the drone further from the center of gravity (the tip of the arm) is lighter than that of the drone 100.

[0112] <Manufacturing method> Figures 30 to 38 are schematic diagrams showing the manufacturing method of arm 1. As described above, arm 1 is formed by connecting two arms 1A and 1B, which are divided into two parts along their longitudinal direction. Arms 1A and 1B are formed by placing a sheet made of carbon fiber reinforced thermoplastic on a male mold, and then heat-press molding the sheet while it is sandwiched between the male and female molds. The outline of the manufacturing process will be described below.

[0113] Arms 1A and 1B are identical in shape and are manufactured one at a time. As shown in Figures 30 and 31, a male mold 30 and a female mold 32 are placed in a heated press molding machine. Hereafter, only arm 1A will be referred to. As shown in Figures 32(a) and (b), the male mold 30 is the mold for the inner surface of arm 1A. Grooves 12pre are formed in the male mold 30 for forming the protrusions 12a and 12b of arm 1A. As shown in Figures 33(a) and (b), the female mold 32 is the mold for the outer surface of arm 1A.

[0114] Figure 34(a) shows material 2 of arm 1A. Material 2 is a sheet of carbon fiber reinforced thermoplastic plastic (hereinafter referred to as "material sheet"). Specifically, TAFNEX® manufactured by Mitsui Chemicals, Inc. was used as the material sheet. TAFNEX is a unidirectional tape (UD tape) that is a composite of carbon fiber and polypropylene (thermoplastic resin).

[0115] As shown in Figure 34(b), multiple material sheets 2 are placed on the male mold 30. In this embodiment, five material sheets 2 are stacked and placed on the male mold 30.

[0116] Next, as shown in Figures 35 and 36, the material sheet 2 was heated and pressurized in the male mold 30 and the female mold 32. The molding conditions were displayed on the panel 42 of the operating device 40 (see Figure 37).

[0117] After the predetermined process is completed, the male mold 30 and the female mold 32 are separated, and the arm 1A (1B) is formed as shown in Figure 38. Figure 38(a) shows the outer surface of the arm 1A (1B), and Figure 38(b) shows the inner surface of the arm 1A (1B).

[0118] During the heat press molding process, the material 2 enters the groove 12pre formed in the male mold 30, thereby forming the protrusions 12a and 12b (see Figure 38(b)). The weight of the arm 1A (1B) is 24.9 grams (g), which is about 20% lighter than the conventional product (see Figure 40).

[0119] Arms 1A and 1B are bonded together (see Figure 16), and together they form a single unit: arm 1. For example, a room-temperature plasma treatment can be used as the bonding method.

[0120] It should be noted that the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Explanation of Symbols]

[0121] 1. Arm for drone 1A Upper part of the drone arm 1B Lower part of the drone arm 10. Arm body 20 Connection part 30 Fixed part

Claims

1. In a drone that obtains thrust by the rotation of multiple propellers, a drone arm for arranging a housing that houses the drone's control device and battery, and a motor for rotating the propellers, at a predetermined distance from each other, The aforementioned arm is It extends outward from the housing and is positioned in a location through which the airflow generated by the rotation of the propeller, which is connected to the motor's rotation shaft, flows. The hollow arm body, the connecting part for connecting to the housing, and the fixing part for fixing the motor are integrally formed from carbon fiber reinforced thermoplastic plastic. When the shape of the outer circumference of the cross-section of the arm body in a direction perpendicular to the longitudinal direction of the arm body is defined by the maximum height and the maximum width perpendicular to the maximum height, the maximum height is formed to be greater than the maximum width. When the line corresponding to the maximum height is taken as the center line, the outer circumference is formed symmetrically with respect to the center line. The upper part of the outer circumference of the arm body, which corresponds to the maximum height, is configured to be positioned as close as possible to the rotation surface of the propeller. The outer circumference is formed such that, compared to the case where the outer circumference of the cross-section of the arm body is circular, the airflow generated by the rotation of the propeller reduces the amount by which the thrust generated by the rotation of the propeller decreases.

2. In the outer circumference, when the direction in which the center line extends is defined as the vertical direction, and the portion of the outer circumference opposite to the upper part is defined as the lower part, the width of the outer circumference, which is perpendicular to the vertical direction, is configured to be largest at the widest portion, which is the portion with the maximum width, and to decrease as it moves towards the upper part and towards the lower part. The drone arm according to claim 1.

3. The maximum width portion is formed at an intermediate position between the upper and lower parts in the vertical direction. The drone arm according to claim 2.

4. The maximum width portion is formed in a position closer to the upper part than to the lower part. The drone arm according to claim 2.

5. The drone arm according to claim 2, wherein the maximum width portion is formed at a position closer to the upper part than the midpoint between the upper part and the lower part.

6. The drone arm according to claim 2, wherein the maximum width portion is formed at a position closer to an intermediate position between the upper and lower parts than the upper part.

7. When considering an intermediate position between the upper part and the lower part, if the distance from the upper part to the intermediate position is defined as the first distance, and the distance from the upper part to the maximum width portion is defined as the second distance, the ratio of the second distance to the first distance is 30 / 100 or more and 85 / 100 or less, as described in claim 2, for a drone arm.

8. The drone arm according to claim 4, wherein the radius of curvature of the outer circumference in the upper vicinity, including the upper part, is smaller than the radius of curvature of the part other than the upper vicinity.

9. The drone arm according to any one of claims 1 to 8, wherein the outer circumference does not include straight lines and is formed only by curves.

10. The drone arm according to any one of claims 1 to 8, wherein when an airflow is directed from the upper part to the lower part of the arm body, the difference between the pressure of the airflow near the upper part and the pressure of the airflow near the lower part is smaller than when the outer circumference of the cross-section of the arm body is circular.

11. The drone arm according to any one of claims 1 to 8, wherein a projection extending in a direction intersecting the longitudinal direction of the arm body is formed on the inner surface of the arm body, extending over the entire length of the arm body.

12. A drone having an arm for a drone as described in any one of claims 1 to 8.

13. A method for manufacturing a drone arm in which a drone that obtains thrust by the rotation of multiple propellers arranges a housing for the drone's control device and battery and a motor for rotating the propellers at a predetermined distance from each other, The aforementioned drone arm is The hollow arm body, the connecting part for connecting to the housing, and the fixing part for fixing the motor are integrally formed from carbon fiber reinforced thermoplastic plastic. The aforementioned drone arm is formed by connecting two arm members, each having a shape that is divided into two along the longitudinal direction. The arm member is formed by placing a sheet made of carbon fiber reinforced thermoplastic on a male mold, and then heat-press molding the sheet while it is sandwiched between the male and female molds. A method for manufacturing arms for drones.

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