Multicopter

Abstract

To decrease air resistance in horizontal movement in a multicopter having a ducted rotor.SOLUTION: A multicopter is equipped with a plurality of rotors 18, and a plurality of ducts 20 respectively surrounding outer peripheries of the rotors 18. On a surface of the duct 20 turning outward of a machine body of the multicopter, an outer peripheral protrusion 28 protruding outward in a diametrical direction of the duct and extending in a circumferential direction of the duct 20 is provided. The outer peripheral protrusion 28 is a concave surface in which a center portion projects out in a direction along a rotation axis A of the rotor 18, projection amount is gently reduced from the center portion toward side edges on both sides, and parts between the center portion and the side edges are smoothly curved.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to multicopters, and in particular to multicopters having ducted rotors. [Background technology]

[0002] An aircraft equipped with multiple rotors, so-called a multicopters, is known. Also known is a multicopters employing a ducted rotor, which is a rotor combined with a duct surrounding the periphery. By surrounding the periphery of the rotor with a cylindrical duct, it is possible to suppress the generation of vortexes at the outer periphery of the rotor and improve the efficiency of the rotor. Patent Document 1 below shows an aircraft (2) in which the periphery of each of four rotors (propellers 21 to 24) is surrounded by cylindrical dust collectors (4-1 to 4-4). Note that the reference characters and component names in parentheses are those used in Patent Document 1 below and are not related to the reference characters and component names used in the description of the embodiments of the present application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6872681 Summary of the Invention [Problem to be solved by the invention]

[0004] In a multicopters, the direction of travel intersects with the axis of rotation of the rotor, so providing a duct surrounding the outer periphery of the rotor increases the projected area of ​​the aircraft in the direction of travel, which tends to increase air resistance.

[0005] The present invention aims to reduce air resistance in a multicopter equipped with a ducted rotor. [Means for solving the problem]

[0006] The multicopter according to the present invention includes a plurality of rotors and a duct surrounding the outer periphery of each rotor. Outer circumference The surface is raised radially outward of the duct, and Only in the outer peripheral surface outside the polygon connecting the centers of the rotors An outer circumferential ridge is provided extending circumferentially around the duct, with the central portion of the outer circumferential ridge protruding in the direction of the rotor's rotational axis, and the amount of protrusion gradually decreasing from the central portion to both side edges, with a smoothly curved concave surface between the central portion and the edges. Effect of the Invention

[0007] When the multicopter moves horizontally, the airflow is smoothly redirected in front of it in the direction of movement due to the peripheral ridges, eliminating stagnation in the airflow and reducing air resistance. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a multicopter. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic diagram of one rotor portion (ducted rotor). [Diagram 3] 13A and 13B are diagrams showing other examples of the arrangement of the peripheral protrusions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] FIG. 1 is a perspective view showing a schematic configuration of a multicopter 10 according to the present embodiment. The multicopter 10 includes a main body 12, four rotor units 14 arranged around the main body 12, and legs 16 attached to the underside of the main body 12. As described below, the rotor units 14 are in the form of a ducted rotor including a rotor 18 (see FIG. 2) and a duct 20 surrounding the outer periphery of the rotor 18. The duct 20 is fixed to the main body 12, and the rotor units 14 are integrated with the main body 12. Alternatively, the rotor units 14 may be arranged at the ends of a plurality of arms extending radially from the main body 12. The number of rotor units 14 is not limited to four as shown in the figure, and may be three, six, or another number. The legs 16 are provided in the form of, for example, three or four, and when the multicopter 10 lands, they come into contact with the landing surface and support the aircraft.

[0010] The main body 12 houses a controller that calculates the rotation speed of each rotor to control the attitude, flight direction, flight speed, etc. of the multicopter 10, a rotation control unit that controls each rotor to the calculated rotation speed, a battery as a power source, etc. When the multicopter 10 is remotely controlled by radio, the main body 12 also houses a radio wave transmitter and receiver for that purpose.

[0011] FIG. 2 is a cross-sectional view that shows a cross section of the rotor section 14, particularly a cross section including the rotation axis A of the rotor 18. The cross-sectional shape is common to the four rotor sections 14. The rotor 18 has a plurality of blades 22, for example, two or three blades 22, each of which extends radially outward from the rotation axis A. The rotor 18 is driven to rotate by a motor 24, and generates an airflow along the rotation axis A. A duct 20 is provided to surround the outer periphery of the rotor 18. The inner wall surface 20a of the duct 20 is a cylindrical surface and is close to the outer periphery of the rotor 18, i.e., the tips of the blades 22. At the tip of the blade, the airflow flows from the positive pressure surface beyond the tip of the blade to the negative pressure surface on the opposite side, and this flow generates a so-called blade tip vortex. The inner wall surface 20a of the duct 20 is close to the tip of the blade 22, thereby preventing the airflow from passing over the tip of the blade 22 and suppressing the generation of the blade tip vortex. The inner wall surface 20a of the duct may have a larger diameter at the opening on the airflow inlet side, and may be shaped to smoothly connect to the cylindrical portion around the rotor 18.

[0012] The motor 24 is supported by a plurality of stays 26 extending radially inward from the inner wall of the duct 20, and is supported by the main body 12 via the duct 20. The motor 24 may also be supported by an arm extending from the main body 12, in which case the duct 20 may be supported by the main body 12 via the arm, the motor 24, and the stay 26. The motors 24 are driven to rotate by power from a rotation control unit housed in the main body 12, and the lifting, rotation, horizontal movement, and attitude of the multicopter 10 are controlled by appropriately controlling the rotation speed of each of the motors 24.

[0013] The outer peripheral surface of each duct 20 is provided with an outer peripheral ridge 28 that ridges radially outward and extends along the circumferential direction of the duct 20. The outer peripheral ridge 28 may extend along the entire outer periphery of the duct 20 except for the portion interfering with the main body 12. The duct 20 may have a hollow structure with a hollow interior surrounded by an inner wall 30 that defines the inner wall surface 20a and an outer wall 32 that defines the outer peripheral ridge 28. In addition, partition walls or ribs may be provided in the hollow space inside the duct 20 to ensure the strength and rigidity of the duct 20. Furthermore, the duct 20 may have a solid structure.

[0014] The outer peripheral ridge 28 has a central portion that protrudes most outward in the direction along the rotation axis A. The protruding end of the outer peripheral ridge 28 may have a rounded tip. By making the tip round, damage to an obstacle can be reduced when the outer peripheral ridge 28 comes into contact with the obstacle. The outer peripheral ridge 28 gradually reduces in protrusion amount from the central portion toward the edges on both sides of the duct 20, that is, the upper and lower edges in FIG. 2. The outer peripheral ridge 28 may reach the inner wall surface 20a at the edges on both sides of the duct 20, and these edges may be rounded. Furthermore, the outer peripheral ridge 28 may reach a position radially outward from the inner wall surface 20a at the edges on both sides of the duct 20, in which case the end of the duct 20 has a thickness. Furthermore, the outer peripheral ridge 28 is formed into a smoothly curved concave surface between the central portion and the edges. The cross-sectional shape of the outer peripheral ridge 28 may be constant in the circumferential direction.

[0015] When the multicopter 10 moves in the horizontal direction, the airflow F received by the rotor section 14 smoothly changes direction along the surface of the outer peripheral protrusion 28 as shown in Fig. 2. This eliminates stagnation of the airflow, thereby reducing air resistance.

[0016] In a multicopter in which the rotor portion 14 is coupled to the body 12 via an arm and is located remote from the body 12, the duct 20 may be provided with a peripheral ridge 28 around its entire circumference.

[0017] FIG. 3 is a diagram showing a schematic example of a case where an outer circumferential ridge is provided on a part of the outer circumferential surface of a duct, particularly on the outer circumferential surface facing outward of the multicopter's airframe. FIG. 3 is a diagram showing a multicopter 40 viewed along the rotation axis direction of the rotor. The difference from the multicopter 10 described above is the range in which the outer circumferential ridge is arranged, and the other configurations are the same as those of the multicopter 10. Four rotor parts 42 are arranged around the main body 12. An outer circumferential ridge 46 is provided on a part of the outer circumferential surface of the duct 44 of the rotor part 42. The cross-sectional shape of the outer circumferential ridge 46 is the same as that of the outer circumferential ridge 28 shown in FIG. 2. The outer circumferential ridge 46 extends to the outer range of a polygon 50 connecting the rotor centers O of the rotor parts 42 on the outer circumferential surface of the duct 44. When there are four rotor parts 42, the polygon 50 is a quadrangle as shown in the figure. When there are n rotor parts 42, the polygon 50 is an n-sided polygon.

[0018] The multicopter can move in any direction in a horizontal plane. In the multicopter 40, the portion where the outer peripheral protuberance 46 is provided is a portion that may become the front surface that directly receives the airflow when the multicopter 40 moves horizontally, and providing the outer peripheral protuberance 46 in this portion allows the direction of the airflow to be changed smoothly. In addition, setting a range where the outer peripheral protuberance 46 is not provided contributes to reducing the weight of the aircraft. [Explanation of symbols]

[0019] 10,40 Multicopter, 12 Main body, 14,42 Rotor section (ducted rotor), 16 Leg, 18 Rotor, 20,44 Duct, 22 Blade, 24 Motor, 26 Stay, 28,46 Outer peripheral protrusion, 30 Inner wall, 32 Outer wall, 50 Polygon connecting the centers of the rotor section, A Rotor rotation axis, F Air flow.

Claims

[Claim 1] A plurality of rotors; A duct surrounding an outer periphery of each of the rotors; A multicopter comprising: An outer circumferential surface of the duct is provided with an outer circumferential ridge that bulges outward in the radial direction of the duct and extends along the circumferential direction of the duct only in an area outside a polygon connecting the centers of the rotors on the outer circumferential surface, The outer circumferential protrusion has a central portion protruding in a direction along the rotation axis of the rotor, and the protrusion amount gradually decreases from the central portion toward both side edges, and a smoothly curved concave surface is formed between the central portion and the edge. Multicopter.

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