JP7616134B2 - Multicopter - Google Patents

Description

The present invention relates to a multicopter, in particular a multicopter with a ducted rotor.

Air vehicles equipped with multiple rotors, so-called multicopters, are known. Multicopters that use ducted rotors, which are rotors combined with ducts that surround the periphery of the rotors, are also known. By surrounding the periphery of the rotors with cylindrical ducts, it is possible to suppress the generation of vortexes at the outer periphery of the rotors and improve the efficiency of the rotors. The following Patent Document 1 shows an air vehicle (2) in which the periphery of each of the four rotors (propellers 21 to 24) is surrounded by cylindrical dust collectors (4-1 to 4-4). Note that the reference numbers and component names in parentheses are those used in the following Patent Document 1, and are not related to the reference numbers and component names used in the description of the embodiments of this application.

Patent No. 6872681

In a multicopter, the direction of travel intersects with the axis of rotation of the rotor, so providing a duct that surrounds the outer periphery of the rotor increases the projected area of the aircraft in the direction of travel, which tends to increase air resistance.

The present invention aims to reduce air resistance in a multicopter equipped with a ducted rotor.

The multicopter of the present invention comprises a plurality of rotors and ducts surrounding the outer periphery of each rotor, and the outer peripheral surface of the duct is provided with an outer peripheral ridge that protrudes radially outward from the duct and extends circumferentially of the duct only in an area of the outer peripheral surface outside a polygon connecting the centers of each of the rotors , and the outer peripheral ridge has a central portion that protrudes in the direction of the rotor's rotation axis, and the amount of protrusion from the central portion gradually decreases toward the edges on both sides, forming a smoothly curved concave surface between the central portion and the edges.

When the multicopter moves horizontally, the airflow is smoothly redirected in front of it in the direction of movement due to the ridges on the outer periphery, eliminating stagnation in the airflow and reducing air resistance.

FIG. 1 is a perspective view showing a schematic configuration of a multicopter. FIG. 2 is a cross-sectional view showing a schematic diagram of one rotor portion (ducted rotor). 13A and 13B are diagrams showing other examples of the arrangement of the peripheral protrusions.

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.

The main body 12 houses a controller that calculates the rotational 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 rotational speed, a battery that serves as a power source, etc. When the multicopter 10 is remotely controlled wirelessly, it also houses a radio wave transmitter and receiver for this purpose.

2 is a cross-sectional view showing 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, which prevents the airflow from exceeding the tip of the blade 22, thereby suppressing the generation of the blade tip vortex. The inner wall surface 20a of the duct may be shaped so that the diameter of the opening on the airflow inlet side is larger and smoothly connects to the cylindrical part around the rotor 18.

The motors 24 are supported by a number of stays 26 extending radially inward from the inner wall of the duct 20, and are supported by the main body 12 via the duct 20. The motors 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 motors 24, and the stays 26. The motors 24 are driven to rotate by power from a rotation control unit housed in the main body 12, and the elevation, rotation, horizontal movement, and attitude of the multicopter 10 are controlled by appropriately controlling the rotation speed of each motor 24.

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 around the entire outer periphery of the duct 20, except for the portion that interferes 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, partitions 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.

The outer ridge 28 protrudes most outward in the center in the direction along the rotation axis A. The protruding end of the outer ridge 28 may be rounded. By making the tip round, damage to an obstacle can be reduced when the outer ridge 28 comes into contact with the obstacle. The outer ridge 28 gradually reduces in protrusion from the center toward the edges on both sides of the duct 20, that is, the upper and lower edges in FIG. 2. The outer 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. Also, the outer 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 ridge 28 is formed into a smoothly curved concave surface between the center and the edges. The cross-sectional shape of the outer ridge 28 may be constant in the circumferential direction.

When the multicopter 10 moves horizontally, the airflow F received by the rotor section 14 smoothly changes direction along the surface of the outer circumferential ridge 28 as shown in Figure 2. This eliminates stagnation of the airflow and reduces air resistance.

In a multicopter in which the rotor section 14 is connected to the main body 12 via an arm and is located away from the main body 12, an outer circumferential ridge 28 may be provided around the entire circumference of the duct 20.

3 is a schematic diagram showing an example in which an outer circumferential ridge is provided on a part of the outer circumferential surface of the duct, particularly on the outer circumferential surface facing outward of the multicopter's body. 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 outside of a polygon 50 connecting the rotor centers O of each rotor part 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.

The multicopter can move in any direction in a horizontal plane. The part of the multicopter 40 where the outer circumferential ridge 46 is provided is the part that may become the front surface that is directly exposed to the airflow when the multicopter 40 moves horizontally, and providing the outer circumferential ridge 46 in this part makes it possible to smoothly change the direction of the airflow. In addition, setting an area where the outer circumferential ridge 46 is not provided contributes to reducing the weight of the aircraft.

10, 40 Multicopter, 12 Main body, 14, 42 Rotor portion (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 centers of rotor portions, A Rotor rotation axis, F Air flow.

Claims (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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