Drone propeller blades

Abstract

To provide a propeller for a drone which can suppress personal injury and property damage.SOLUTION: A blade 7 of a propeller 2 for a drone 1 is fixed to a rotation shaft 9 which rotates when receiving rotation power of an electric motor 5, and has impact absorption performance which continuously or gradually changes over an expansion direction of a blade surface of the blade 7. The impact absorption performance of the blade 7 continuously or gradually increases toward a tip end part 14 of which a distance from a hub part 13 fixed to the rotation shaft 9 is large.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention relates to propeller blades that generate lift and thrust for unmanned rotorcraft (hereinafter referred to as drones). [Background technology]

[0002] Remotely controlled drones equipped with multiple electric propellers are stable in flight and easy to control, so they can be equipped with photography equipment and other items and are now widely used in a variety of industrial fields, from hobby purposes to facility inspection and monitoring, and the transportation of goods.

[0003] However, if a drone is misoperated and crashes into a person or equipment, personal injuries such as fingers being cut by the thin propeller blades rotating at high speeds can occur, as well as property damage such as damage to public buildings and industrial equipment.

[0004] Conventional technology has been disclosed to prevent personal injury and property damage caused by such drone propellers (Patent Document 1).

[0005] Patent document 1, "Rotating blade and manufacturing method thereof," discloses a rotating blade having a hub portion fixed to a rotating shaft that rotates when it receives the output of a drive source, and a blade portion fixed from the hub portion to the rotating shaft, in which the blade portion of the rotating blade is made of a flexible material such as rubber, thereby reducing injury to people who come into contact with it and damage to structures, and a manufacturing method thereof. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-104369 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to prevent personal injury and property damage caused by collisions with the propellers of drones rotating at high speeds, circular propeller guards that surround the propellers and aircraft guards that cover the entire aircraft with a mesh of wires are used. However, the installation of propeller guards and aircraft guards increases the weight of the aircraft and increases air resistance during flight, which can significantly affect flight performance, such as shortening flight time and making the aircraft more susceptible to wind.

[0008] Conventional technology that considers safety in the event of a propeller collision includes a rotor blade for an unmanned aircraft in which the entire propeller is made of a flexible material and a manufacturing method thereof (Patent Document 1), but when the propeller blade is made of a highly flexible material, i.e., a material with low rigidity, the blade will bend significantly in the longitudinal direction, causing a loss of lift generated by the blade as it rotates at high speed, which may result in a decrease in flight performance.In addition, since it is believed that most personal injuries and damage to property occur when the propeller blade collides with the portion from the leading edge to the tip, there is no need to construct the entire blade from a highly flexible material.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a drone propeller blade that can reduce personal injury and damage to property. [Means for solving the problem]

[0010] The present invention provides a drone propeller blade that is fixed to a rotating shaft that rotates by receiving rotational power from an electric motor, the blade having shock absorption performance that changes continuously or stepwise across the width of the blade's wing surface.

[0011] The present invention also provides the above-mentioned blade, in which the impact absorbing performance increases continuously or stepwise toward the tip portion which is farther away from the hub portion fixed to the rotating shaft.

[0012] The present invention further provides the above-mentioned blade, in which the impact absorbing performance increases continuously or stepwise from the trailing edge located rearward in the rotation direction of the propeller to the leading edge located forward in the rotation direction.

[0013] The present invention further provides the above-mentioned blade, which is formed from a functionally gradient material in which the composition or structure of the material is changed continuously or stepwise, and the impact absorption performance is controlled continuously or stepwise in accordance with the physical properties of the material.

[0014] The present invention further provides the above-mentioned blade, which is formed with a functionally gradient structure in which the shaping structure is changed continuously or stepwise, and the impact absorbing performance is changed according to the structural characteristics.

[0015] The present invention further provides the above-mentioned blade which is shaped from a foaming material, in which the distribution density and / or diameter of the bubbles or cells is changed continuously or stepwise, and the impact absorption performance is controlled according to the distribution density and / or diameter. Effect of the Invention

[0016] The present invention provides a drone propeller blade that reduces injury to people and damage to structures that come into contact with the propeller blades rotating at high speed, and also ensures the rigidity required to generate lift. [Brief description of the drawings]

[0017] [Figure 1] 1 is a plan view showing an embodiment of a drone 1 to which a blade 7 according to the present invention is applied. [Diagram 2] 1A and 1B are a plan view and a schematic diagram of hardness distribution of a blade 7 according to the present invention, showing an example of two-dimensional distribution of hardness when the longitudinal impact absorption performance of the blade 7 from the hub portion 13 to the tip portion 14 changes continuously. [Diagram 3] 1A and 1B are a plan view and a schematic diagram of hardness distribution of a blade 7 according to the present invention, showing an example of a two-dimensional distribution of hardness when the impact absorption performance in the width direction from the trailing edge 16 to the leading edge 15 of the blade 7 changes continuously. [Figure 4]1A and 1B are plan views and schematic diagrams of hardness distribution of blade 7 showing examples of two-dimensional distribution of hardness when the impact absorption performance of blade 7 of the present invention changes stepwise in the longitudinal direction from hub portion 13 to tip portion 14 and in the width direction from trailing edge portion 16 to leading edge portion 15. [Diagram 5] 4, is a cross-sectional view of the blade 7 showing an example of a two-dimensional distribution of hardness when the density and diameter of bubbles in a cross section perpendicular to the longitudinal direction of the blade 7 change stepwise from the trailing edge 16 to the leading edge 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment of a drone propeller blade according to the present invention will be described with reference to Figures 1 to 5. The present invention is not limited to the following embodiment. Of course, the following components can be omitted or added, and the shapes of the components can be modified without departing from the gist of the present invention. Note that the figures are schematic, depicting only a portion and omitting the detailed structure.

[0019] 1 is a plan view showing an embodiment of a drone 1 to which a blade 7 according to the present invention is applied. The drone 1 is composed of a control unit including a battery 4 and a transceiver, a plurality of connecting arms 11 arranged radially outward from the center of the aircraft body equipped with a camera etc., and a driving unit including an electric motor 5 provided at the tip of the connecting arm 11.

[0020] FIG. 1 shows an example of a drone 1 equipped with four propellers 2. The propellers 2 have two to four blades 7, 7 that extend in a generally elongated shape from a hub portion 13 that is attached perpendicular to a rotating shaft 9 that rotates by receiving power from an electric motor 5 toward a tip portion 14. The hub portion 12 and the blades 7 may be formed separately from each other and fixed so as not to separate from each other during rotation.

[0021] Since personal injury or property damage caused by the blades 7 of a propeller 2 rotating at high speed occurs when the blades 7 collide with each other from the leading edge 15 to the tip 14, the present invention relates to a blade 7 that is formed by imparting flexibility, i.e., shock absorbing performance, to the portion of the blade 7 from the leading edge 15 to the tip 14 while also ensuring the rigidity of the blade 7 necessary to generate lift and propulsion, and relates to a blade 7 that is formed by imparting a continuous or stepwise change in material properties, or a blade 7 that is formed by imparting a continuous or stepwise change in structural properties.

[0022] The blades 7 of the propeller 2 are blades 7 of the drone propeller 2 that are fixed to a rotating shaft 9 that rotates by receiving rotational power from the electric motor 5, and have shock absorbing performance that changes continuously or stepwise across the width direction of the blade 7's wing surface. The direction of spread of the blade surface of the blade 7 refers to the range from the trailing edge 16 to the leading edge 15 in the longitudinal direction from the hub portion 13 to the tip portion 14 of the blade 7 .

[0023] The impact absorption performance of the blade 7 is changed continuously or stepwise, so that the trailing edge 16 side, located rearward in the rotation direction R of the propeller 2, has low impact absorption performance but ensures hardness and rigidity, suppressing bending deformation of the blade 7 when the drone 1 is flying and reducing loss of lift, while the leading edge 15 and tip 14 near the tip 14, where the risk of people or structures coming into contact with the propeller 2 rotating at high speed, are the most likely to have high impact absorption performance. Impact absorption performance indicates the degree to which an impact can be absorbed when a material collides with a person or structure, and can be expressed by various numerical values, such as the physical material properties of the material used, such as the hardness and density, or the structural properties, such as the size and distribution density of the air bubbles or cells contained in the material.

[0024] FIG. 2 is a plan view of blade 7 and a schematic diagram of hardness distribution showing an example of two-dimensional distribution of material hardness when the longitudinal impact absorption performance of blade 7 according to the present invention changes continuously from hub portion 13 to tip portion 14. The blades 7 are formed so that the shock absorbing performance continuously increases from a hub portion 13 fixed to the rotating shaft 9 toward the tip portions 14 of the blades 7 . The blade 7 includes a hub portion 13 fixed to the rotary shaft 9 and a peripheral portion thereof, which are constituted by a rigid portion 10 that ensures rigidity. On the other hand, the hardness of the material is continuously reduced toward the tip portion 14 and its surrounding area, which is farther away from the hub portion 13, and the shock absorbing portion 6 has increased shock absorbing performance. Note that Fig. 2 shows an example in which about two-thirds of the longitudinal blade surface from the hub portion 13 to the tip portion 14 of the blade 7 is made up of the rigid portion 10, and the remaining tip portion 14, which is about one-third, is made up of the shock absorbing portion 6, and the ratio of the rigid portion 10 to the shock absorbing portion 6 is adjusted as appropriate.

[0025] FIG. 3 is a plan view of a blade and a schematic diagram of hardness distribution showing an example of two-dimensional distribution of material hardness when the impact absorption performance in the width direction of the blade 7 according to the present invention changes continuously from the trailing edge 16 to the leading edge 15. The blade 7 is formed so that the shock absorbing performance of the material increases continuously from the trailing edge 16 located rearward in the rotation direction R of the propeller 2 to the leading edge 15 located forward in the rotation direction R of the propeller 2. The trailing edge 16 and its vicinity of the blade 7 are made up of a rigid section 10 that ensures rigidity. On the other hand, the blade 7 is made up of a shock absorbing section 6 that has a continuously reduced hardness and rigidity toward the leading edge 15 and has increased shock absorbing performance. Note that Fig. 3 shows an example in which about two-thirds of the blade surface in the width direction from the trailing edge 16 to the leading edge 15 of the blade 7 is made up of the rigid section 10, and the remaining about one-third, the leading edge 15 and its vicinity, is made up of the shock absorbing section 6, and the ratio of the rigid section 10 to the shock absorbing section 6 is adjusted as appropriate.

[0026] The blade 7 is made of a functionally gradient material in which the composition or structure of the material is changed continuously or stepwise to control the physical properties of the material continuously or stepwise. For example, the blade 7 is made of a functionally gradient material in which the material properties such as hardness and rigidity are changed continuously or stepwise by changing the ratio or amount of compounding agents added to the material continuously or stepwise, or the material properties such as hardness and rigidity are changed continuously or stepwise by changing the ratio of the materials to be mixed. In addition, a 3D printer or the like can be used for the molding, and two or more different materials can be combined and layered to increase the impact absorption performance, such as density and hardness, of the leading edge 15 of the blade 7 and its vicinity to the tip of the blade 7, so as to absorb the impact when it comes into contact with a person or structure. It should be noted that the blade 7 can be manufactured by various methods other than those described above.

[0027] The present invention is not limited to the embodiments shown in FIGS. 2 and 3, and various configurations can be applied. For example, although not shown, the blade 7 may be formed from a functionally gradient material whose impact absorption performance continuously increases in the longitudinal direction from the hub portion 13 fixed to the rotating shaft 9 toward the tip portion 14 of the blade 7, and in the width direction from the rear edge portion 16 to the leading edge portion 15 of the blade 7, and from the hub portion 13 toward the corner of the tip of the blade 7 where the leading edge portion 15 and the tip portion 14 intersect.

[0028] 4 is a plan view of a blade 7 according to the present invention, showing an example of two-dimensional distribution of hardness when the impact absorption performance of the blade 7 changes stepwise in the longitudinal direction from the hub portion 13 to the tip portion 14 and from the trailing edge portion 16 to the leading edge portion 15. The blade 7 has a porous structure in which a part of the blade 7 from the leading edge portion 15 to the tip portion 14 and its vicinity have cavities like large and small bubbles dispersed inside the material, and the example of the distribution of bubbles is shown when the blade 7 is viewed in plan. The blade 7 is a blade 7 of a propeller 2 for a drone 1 fixed to a rotating shaft 9 that rotates by receiving rotational power from an electric motor 5, and forms a gradient functional structure in which the impact absorption performance changes continuously or stepwise in the direction of the spread of the wing surface of the blade 7 depending on the structural characteristics of the material. The structural characteristics of a material refer to the structural features and performance of a porous structure formed into a foamed or porous shape. A functionally graded structure, in which the shock absorption performance changes according to the structural characteristics of the material, is a structure in which the shock absorption performance of the porous structure changes continuously or stepwise in the size, shape, arrangement, etc. of the bubbles.

[0029] Specifically, the blade 7 has a gradient functional structure in which the density and diameter of the air bubbles increase in the longitudinal direction from the hub portion 13 fixed to the rotating shaft 9 to the tip portion 14 of the blade 7, and in the width direction from the trailing edge portion 16 to the leading edge portion 15 of the blade 7, thereby forming a gradient functional structure in which the shock absorption performance increases in stages. The distribution density of bubbles means the total volume of bubbles per unit volume of the structure. The blade 7 includes a hub portion 13, a trailing edge portion 16, and the vicinity thereof, which are constituted by a solid, hard rigid portion 10 that ensures rigidity. Meanwhile, the tip portion 14, the front edge portion 15 and their vicinity are constituted by a low-resilience shock absorbing portion 6 in which the density and diameter of the air bubbles are increased to reduce hardness and increase shock absorbing performance. Between the rigid portion 10 and the shock absorbing portion 6, an intermediate portion 8 is provided, in which the density and diameter of the air bubbles are smaller than those of the shock absorbing portion 6 and which has a hardness between that of the rigid portion 10 and the shock absorbing portion 6.

[0030] In this embodiment, the hardness of the blade 7 is divided into three sections: the rigid section 10, the intermediate section 8, and the shock absorbing section 6. However, the present invention is not limited to this embodiment, and the blade 7 may be divided into two sections, the rigid section 10 and the shock absorbing section 6, without the intermediate section 8, or may have a more finely divided distribution. The cells of the functionally gradient structure can have various structures, such as open cells, a plurality of closed cells, or a mixture of open cells and closed cells. Regarding the bubbles of the functionally gradient structure, various structures can be appropriately adopted, such as a structure in which both the density and the diameter are changed stepwise or continuously, or a structure in which either the density or the diameter is changed stepwise or continuously.

[0031] FIG. 5 is a cross-sectional view taken along line II in FIG. 4, showing a cross-sectional view of a blade 7 of a propeller 2, illustrating an example of a two-dimensional distribution of hardness when the density and diameter of bubbles in a cross section perpendicular to the longitudinal direction of the blade 7 change stepwise from the trailing edge 16 to the leading edge 15. The blade 7 has a plurality of bubbles, the density and diameter of which increase from the trailing edge 16 to the leading edge 15, forming a functionally gradient structure. The blade 7 is configured with a solid rigid portion 10 that ensures rigidity at the trailing edge portion 16 and in the vicinity of the trailing edge portion 16 . On the other hand, the front edge portion 15 and the vicinity of the front edge portion 15 are constituted by a shock absorbing portion 6 in which the density and diameter of the air bubbles are increased to enhance the shock absorbing performance. Between the rigid portion 10 and the shock absorbing portion 6, an intermediate portion 8 is provided, in which the density and diameter of the bubbles are smaller than those of the shock absorbing portion 6 and which has a hardness between that of the rigid portion 10 and the shock absorbing portion 6.

[0032] Methods for producing cellular materials include incorporating gas bubbles into the material through chemical reactions using compounding agents added to the material, or through mechanical mixing of the material. In addition, by using a 3D printer or the like, it is possible to continuously or gradually change the foaming state inside the material from a solid and dense material state, thereby forming a blade 7 that changes continuously or gradually from a rigid section 10 that is hard and has sufficient rigidity to a shock absorbing section 6 that is soft and has low rigidity.

[0033] The present invention is not limited to the embodiment shown in Fig. 5, and various configurations can be applied. For example, although not shown, the blade 7 may have a functionally gradient structure in which the density and / or diameter of the air bubbles and the impact absorbing performance increase stepwise only in the longitudinal direction from the hub portion 13 fixed to the rotating shaft 9 toward the tip portion 14 of the blade 7. Also, the blade 7 may have a functionally gradient structure in which the density and / or diameter of the air bubbles and the impact absorbing performance increase stepwise only in the width direction from the rear edge portion 16 toward the leading edge portion 15 of the blade 7.

[0034] In the case where the material of the blade 7 has a large number of air bubbles open on the surface thereof, the surface of the blade 7 may be covered with a smooth film to reduce air resistance.

[0035] As described above, according to this embodiment, when the drone 1 is flying and a person or structure comes into contact with the propeller 2 rotating at high speed, the leading edge 15 near the tip 14 of the propeller 2 blade 7 where the person or structure comes into contact and the tip 14 are configured with high impact absorption performance, thereby reducing personal injury and damage to property, and further, the rigidity of the hub portion 13, the trailing edge 16 and their surrounding areas is ensured, thereby ensuring the lift required during flight. [Industrial Applicability]

[0036] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made to the configuration without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0037] 1. Drone 2 Propellers 3. Casing 4. Battery 5. Electric motor 6. Shock absorbing section 7 Blade 8. Middle Section 9 Rotation Axis 10 Rigid body part 11 Connecting arm 12 Insert hole 13 Hub section 14 Tip 15 Leading edge 16 Trailing edge R Propeller 2 rotation direction

Claims

1. A drone propeller blade that is fixed to a rotating shaft that rotates by receiving the rotational power of an electric motor, the blade having a shock absorbing performance that changes continuously or stepwise over the width direction of the blade's wing surface, The blade is formed with a functionally gradient structure in which the distribution density and / or diameter of bubbles or cells are changed continuously or stepwise, and the impact absorption performance is controlled according to the distribution density and / or diameter, by using a foaming material; The impact absorption performance increases continuously or stepwise in a width direction from a trailing edge portion located rearward in a rotation direction of the propeller to a leading edge portion located forward in the rotation direction, The trailing edge and its vicinity are made of a solid rigid portion that ensures rigidity and suppresses bending deformation of the blade during drone flight to reduce loss of lift, The front edge portion and its vicinity are constituted by a low-resilience shock absorbing portion in which the density and diameter of the bubbles are increased to reduce rigidity and increase shock absorbing performance when a person or structure comes into contact with the front edge portion and the vicinity thereof; A blade having an intermediate portion between the rigid portion and the shock absorbing portion, the intermediate portion having a smaller bubble density and diameter than the shock absorbing portion and having a hardness between that of the rigid portion and the shock absorbing portion.

2. In the longitudinal direction from the hub portion fixed to the rotating shaft toward the tip portion of the blade, the impact absorption performance increases continuously or stepwise, The hub portion and its vicinity are constituted by the rigid portion, The blade according to claim 1 , wherein the tip portion and its vicinity are constituted by the shock absorbing portion.

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