WO2021085588A1

WO2021085588A1 - Propeller

Info

Publication number: WO2021085588A1
Application number: PCT/JP2020/040775
Authority: WO
Inventors: アンヴァンホ; ディンクアンググエン
Original assignee: 国立大学法人北陸先端科学技術大学院大学
Priority date: 2019-10-31
Filing date: 2020-10-30
Publication date: 2021-05-06
Also published as: JP7236171B2; JPWO2021085588A1

Abstract

A propeller (1) is equipped with: a hub (11); a blade (12) formed so as to extend outward from the hub (11); a curved section (13) which includes a flexible member for connecting the hub (11) and the blade (12); and a cord (15) which is positioned inside the curved section (13) and is stretched between the hub (11) and the blade (12). The blade (12) of the propeller (1) includes a deformable edge (14) positioned on the front side thereof in the direction of rotation (D), and said deformable edge (14) may be flexible.

Description

propeller

The present invention relates to a propeller.

An airplane propeller is a device that includes a plurality of rotary blades (blades) attached to a rotating shaft, and obtains thrust or lift by rotating these blades.
Propellers are also used in small unmanned aerial vehicles, so-called drones.

As such a propeller, Patent Document 1 describes a propeller provided with a rotary blade having a shape suitable for hovering a drone.
This propeller comprises a rotor with long chords near the axis of rotation and stability suitable for hovering.

Patent Document 2 describes a propeller made of a flexible material.
The rotating shaft and rotor blades of this propeller are made of a flexible material.

International Publication No. 2017/146028 Japanese Unexamined Patent Publication No. 2019-104369

The propeller described in Patent Document 1 includes a wing having a shape optimized for maximizing flight time and load.
The wings of this propeller are formed into an unchanging shape for maximum flight time and load. Therefore, the rigidity of the propeller described in Patent Document 1 is high, and there is a problem that the wing is permanently deformed when the propeller collides with another object.

Since the propeller blade described in Patent Document 2 has flexibility as a whole, there is a problem that when the rotation speed increases, the blade twists or vibration is generated in the entire propeller, resulting in continuous deformation. is there.

In view of the above problems, an object of the present invention is to provide a propeller that easily returns to its original shape even if it is deformed during rotation.

In order to achieve the above object, the propeller according to one aspect of the present invention is
In the center and
A blade formed so as to extend outward from the central portion,
A bent portion including a flexible member connecting the central portion and the blade, and a bent portion.
Fibers arranged inside the bent portion and stretched between the central portion and the blades, and
To be equipped.

The blade of the propeller according to the present invention includes a front edge portion located on the front side in the rotation direction.
The front edge portion may have flexibility.

According to the present invention, a propeller that easily returns to its original shape even if it is deformed during rotation is provided.

It is a perspective view of the propeller which concerns on 1st Embodiment. It is a top view of the propeller shown in FIG. 1A. It is a front view of the propeller shown in FIG. 1A. It is a side view of the propeller shown in FIG. 1A. It is a flowchart which shows the flow of the manufacturing method of the propeller shown in FIG. 1A. It is a perspective view of the propeller which concerns on a comparative example. It is a graph which shows the measurement result of the experiment which compared the propeller shown in FIG. 1A and the propeller shown in FIG. 3A. It is a figure which shows the image before and after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 1A comes into contact with an obstacle. It is a figure which shows the image before and after the propeller shown in FIG. 3A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 3A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 3A comes into contact with an obstacle. It is another figure which shows the image before and after the propeller shown in FIG. 3A comes into contact with an obstacle. It is a figure which shows the image immediately after the propeller shown in FIG. 1A came into contact with an obstacle. It is another figure which shows the image immediately after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image immediately after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image immediately after the propeller shown in FIG. 1A comes into contact with an obstacle. It is another figure which shows the image immediately after the propeller shown in FIG. 1A comes into contact with an obstacle. It is a top view of the propeller which concerns on another comparative example. It is a top view of the propeller which concerns on another comparative example. It is a top view of the propeller which concerns on another comparative example. FIG. 7B is a diagram showing an image immediately after the propeller shown in FIG. 7B comes into contact with an obstacle. It is a figure which shows the image immediately after the propeller shown in FIG. 7C came into contact with an obstacle. It is a figure which shows the image immediately after the propeller shown in FIG. 7A came into contact with an obstacle. It is a graph which shows the measurement result of another experiment which compares propellers shown in FIG. 7A to FIG. 7C. It is a top view of the propeller which concerns on another comparative example. It is a top view of the propeller which concerns on another comparative example. It is a top view of the propeller which concerns on another comparative example. It is a graph which shows the simulation result which compares propellers shown in FIGS. 9A to 9C. It is a perspective view of the propeller which concerns on another comparative example. It is a figure which shows the position of the tip of the wing part of the propeller shown in FIG. 7B. It is a figure which shows the position of the tip of the wing part of the propeller shown in FIG. 10A. It is another figure which shows the position of the tip of the wing part of the propeller shown in FIG. 7B. It is another figure which shows the position of the tip of the wing part of the propeller shown in FIG. 10A. It is a graph which shows the measurement result of another experiment which compares the propeller shown in FIG. 7B and the propeller shown in FIG. 10A. It is a graph which compares the lift measured by an experiment with the predicted lift. It is another graph which compares the lift measured by an experiment with the predicted lift. It is a figure which shows another image immediately after the propeller shown in FIG. 1A comes into contact with an obstacle. It is a figure which shows another image immediately after the propeller shown in FIG. 3A comes into contact with an obstacle. It is a graph which shows the measurement result of another experiment which compares the propeller shown in FIG. 1A and the propeller shown in FIG. 3A. It is a top view of the propeller which concerns on 2nd Embodiment.

The

propellers

1 and 21 according to the embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment)
The propeller 1 according to the first embodiment of the present invention is, for example, a two-blade propeller attached to a drone.

As shown in FIG. 1A, the propeller 1 bends a hub 11 which is a central portion capable of rotating, a wing portion 12 including a pair of blades extending outward from the hub 11, and the hub 11 and the wing portion 12. A flexion portion 13 that is possibly connected, a deformable edge 14 provided at the edge of the wing portion 12, and a plurality of fibrous tendons 15 that are embedded in the flexion portion 13 and connect the hub 11 and the wing portion 12 To be equipped.

Hereinafter, the extending direction of the wing portion 12 shown in FIG. 1A will be described as the + Y direction, the direction in which lift is generated will be described as the + Z direction, and the directions perpendicular to the Y and Z directions will be described as the + X direction.

As shown in FIGS. 1A and 1B, the hub 11 is arranged at the center of the propeller 1. The hub 11 is a central portion that connects the rotation axis of the propeller 1 with other members of the propeller 1. At the center of the hub 11, a hole H for connecting to the rotation shaft of the motor M (not shown) is threaded in the Z direction. The hub 11 includes an annulus R and a transition portion T formed so as to continuously and smoothly project radially outward from the annulus R. At one end of the transition portion T, the hub 11 is connected to the bent portion 13. The hub 11 contains a rigid plastic material having high rigidity, for example, ABS resin or PLA (polylactic acid) resin.

Like the hub 11, the wing portion 12 contains a highly rigid hard plastic material.
The blade portion 12 is formed in a shape that functions as a rotary blade (blade) of the propeller 1 integrally with the deformable edge 14 described later.
The specific shape of the propeller 1 may be calculated theoretically or by simulation, and is not limited to the shapes shown in FIGS. 1A to 1D.

The bent portion 13 contains a material having higher flexibility than the hub 11 and the wing portion 12, for example, silicone rubber. Further, the rigidity of the bent portion 13 is lower than the rigidity of the hub 11 and the wing portion 12. The bent portion 13 is arranged between the hub 11 and the wing portion 12, and is formed in a continuously changing shape that smoothly connects the transition portion T located on the outside of the hub 11 and the inside of the wing portion 12. Has been done. By bending the bent portion 13, the wing portion 12 can be displaced in the vertical direction and the rotational direction.

As shown in FIGS. 1B and 1C, the deformable edge 14 is a front edge portion provided on the edge of the wing portion 12 in the rotation direction D. The rotation direction D is counterclockwise in the propeller 1.
The deformable edge 14, like the bent portion 13, contains a material that is more flexible than the hub 11 and the wing portion 12, such as silicone rubber. The rigidity of the deformable edge 14 is lower than the rigidity of the hub 11 and the wing portion 12.
The wing portion 12 is an example of the rear wing portion in the claim, and the deformable edge 14 is an example of the front edge portion in the claim.

The tendon 15 is a thread-like member containing a flexible and high-strength fiber material, for example, nylon fiber. As shown by the broken line in FIGS. 1A to 1C, a plurality of tendons 15 are stretched between the hub 11 and the wing portion 12, and the periphery thereof is covered with the flexion portion 13. The rigidity of the tendon 15 is lower than the rigidity of the flexion portion 13, and the flexibility of the tendon 15 is higher than the flexibility of the flexion portion 13.

As described above, in the propeller 1, the hub 11 and the wing portion 12 have low flexibility, while the bent portion 13 has high flexibility and the tendon 15 having high strength connects the wing portion 12 to the hub 11. There is. Therefore, when the propeller 1 receives an external force, the wing portion 12 and the deformable edge 14 are displaced by the external force, but when the external force disappears, the wing portion 12 and the deformable edge 14 are quickly returned to their original positions. Further, since the propeller 1 contains only a partially flexible material, twisting and vibration due to rotation are reduced as compared with the case where the propeller 1 is entirely composed of the flexible material.

Next, a method of manufacturing the propeller 1 will be described with reference to FIG.
First, the shape of the propeller 1 is designed (step S1). Specifically, for example, using numerical calculation software, a simulator, CAD (Computer Aided Design) software, etc., each component of the propeller 1, that is, a hub 11, a wing portion 12, a bending portion 13, a deformable edge 14, and the like can be used. Design the shape.

Using the design data generated in step S1 and the 3D printer, 3D printing of the hard parts, that is, the hub 11 and the wing portion 12 is performed (step S2).
It should be noted that a hard part may be formed by molding using a mold as in the method in the molding step described later without using a 3D printer.

The hard part and the tendon 15 are adhered to form a frame which is the skeleton of the propeller 1 (step S3). Specifically, since small holes are formed on the surfaces of the hub 11 and the wing portion 12 facing each other, the tendon 15 coated with the adhesive is inserted into these small holes and fixed. For adhesion, an adhesive suitable for both the hard part and the tendon 15 is used.

The frame formed in step S3 is placed on the mold and positioned (step S4). The mold used in this step is formed in advance by a method such as 3D printing from the data of the space occupied by the hub 11, the wing portion 12, the bending portion 13, and the deformable edge 14 generated in the design step.

Perform molding (step S5). For example, a mixture of the main material and the curing agent is poured into a mold and gently held until it hardens.

Separate the molded product from the mold (step S6). In this step, excess parts, so-called burrs, are removed from the molded product.

Fine adjustment is performed by applying an adhesive to the mutually contacting portions of the hub 11, the wing portion 12, the bent portion 13, and the deformable edge 14 (step S7). As a result, the hard part and the soft part of the propeller 1 are more firmly connected.
Propeller 1 is completed through the above steps.

The experiment for investigating the characteristics of the propeller 1 manufactured by the configuration and the manufacturing method described so far will be described.

(First experiment)
An experiment was conducted to measure the lift generated by the propeller 1 when the rotation speed of the propeller 1 was changed.
In order to accurately measure the lift generated by the propeller 1, the lift of the propeller 1 was measured as a tensile force using a digital force gauge.
Further, as shown in FIG. 3A, a conventional propeller 101 having the same shape as the propeller 1 and made of only a hard material was used as a comparative example.

In the following experiment to rotate the propeller, the propeller was connected to the rotation shaft of the motor M, and the rotation speed of the motor M could be set arbitrarily by changing the current supplied to the motor M. In the following experiment, since the propeller is directly connected to the motor M, the rotation speed of the propeller is equal to the rotation speed of the motor M.

FIG. 3B shows the relationship of lift (N) with respect to the rotational speed (rpm) of the motor M.
As shown in FIG. 3B, when the rotation speed is increased, the lift generated by the propeller 1 is linearly increased as in the lift generated by the conventional propeller 101.
Further, when compared at the same rotation speed, the lift obtained by using the propeller 1 is about 22.6% smaller than the lift obtained by using the conventional propeller 101. However, by increasing the rotation speed, it was obtained that the lift force of the propeller 1 can be obtained to the same level as that of the conventional propeller 101.

From this experiment, the following can be understood.
The lift produced by the flexible propeller 1 is smaller than the lift produced by the conventional propeller 101 having the same shape. However, by increasing the rotation speed, the flexible propeller 1 can generate lift equivalent to that of the conventional propeller 101. Therefore, even if the conventional propeller 101 is replaced with the flexible propeller 1, it is considered that the flight of the drone will not be hindered.

(Second experiment)
An experiment was conducted to examine the presence or absence of damage to the obstacle when the rotor was brought into contact with the obstacle, and the degree of damage to the propeller 1 and the conventional propeller 101.
As an obstacle, a polypropylene ribbon having a width of 3 mm and a thickness of 0.2 mm was used. The ribbon was stretched in the Z direction, and the propeller 1 or the propeller 101 was arranged so that the tip of the propeller 1 or the propeller 101 collided with the vicinity of the center of the ribbon. Further, the rotation speed of the propeller 1 was set to 3200 rpm, and the rotation speed of the propeller 101 was set to 2800 rpm. These rotation speeds are the maximum speeds of the

propellers

1 and 101, and as can be understood from the results of the first experiment, they are all set as conditions for generating a lift of about 1.3 N.

4A-4D and 5A-5D are high-speed camera images taken before and after the moment when the propeller 1 and the propeller 101 touch the ribbon, respectively. 4A to 4D and 5A to 5D are all arranged in the order in which time has passed.

At the time of FIGS. 4A and 5A, neither propeller 1 nor propeller 101 is in contact with the ribbon yet.
At the time points of FIGS. 4B and 5B, the propeller 1 and the propeller 101 were in contact with the ribbon, respectively.
At the time points of FIGS. 4C and 5C, the wing portion 12 of the propeller 1 was bent, but the shape of the ribbon did not change. Further, at this point, the rotary blade of the propeller 101 is not bent, but the shape of the ribbon is changed so as to be bent.
From FIGS. 4D and 5D, it is understood that the wing portion 12 of the propeller 1 is not bent and the shape of the ribbon is not changed, and that the rotor blade of the propeller 101 is not bent but the ribbon is completely broken. Ribbon.

From this experiment, at a high rotational speed that produces the same lift, contact of the propeller 1 with an obstacle does not cause damage to the propeller 1 itself or the contacted object, but the propeller 101 may damage the contacted object. Is understood.

(Third experiment)
An experiment was conducted to investigate the deformation of the propeller 1 when the propeller 1 was brought into contact with an obstacle.
As an obstacle, a model of a human finger with a nylon fiber core embedded was used. Further, the rotation speed of the propeller 1 was set to 3200 rpm.

FIGS. 6A to 6E are high-speed camera images taken after the propeller 1 comes into contact with an obstacle, respectively. 6A to 6E are arranged in the order in which time has passed.

The images shown in FIGS. 6A and 6B are an image immediately after one of the wing portions 12 of the propeller 1 comes into contact with an obstacle, and an image immediately after the other comes into contact with an obstacle. From these images, it is understood that when the wing portion 12 comes into contact with an obstacle, the propeller 1 bends significantly at the bent portion 13.
The image shown in FIG. 6C is an image in the process of pulling out an obstacle upward while rotating the propeller 1. From this image, it is understood that the wing portion 12 twists downward to avoid obstacles.
The images shown in FIGS. 6D and 6E are images immediately after the obstacle is removed. From these images, it is understood that when the obstacle is removed, the shapes of the wing portion 12 and the bent portion 13 are restored.
Since the time elapsed from the acquisition of the image shown in FIG. 6A to the acquisition of the image shown in FIG. 6E is about 0.4 seconds, the propeller 1 collides with an obstacle and is deformed. The time required to return to the original shape is also about 0.4 seconds.

From this experiment, according to the propeller 1, when it comes into contact with the fingers of a human hand, the bent portion 13 bends, twists, and returns to an obstacle in a relatively short time of less than 1 second. It is understood that the impact force due to contact with is absorbed.

(Fourth experiment)
An experiment was conducted in which the shape of the bent portion 13 was changed and the time required for the propeller 1 to return to the original shape after colliding with an obstacle and the magnitude of the lift generated by the propeller 1 were examined.
As shown in FIGS. 7A, 7B, and 7C, the

propellers

201, 301, and 401 according to the comparative example have the same outer shape as the bent portion 13.
The flexed portions 213 to 413 of the propellers 201 to 401 are provided with six tendons 15 each. The diameters of the bent portions 213 to 413 are all 0.62 mm. The lengths of the bent portions 213 to 413 are different from each other, the length of the bent portion 213 is L1 = 6 mm, the length of the bent portion 313 is L2 = 12 mm, and the length of the bent portion 413 is L3 = 18 mm.

The length of the bent portion 13 of the propeller 1 shown in FIG. 1A is L2 = 12 mm.
The bent portions 213 to 413 include a flexible material like the bent portion 13, but are molded using a material that is harder than the bent portion 13.

8A, 8B, and 8C show changes in shape immediately after the

propellers

301, 401, and 201 collide with a resin prism imitating a human finger, respectively. For example, "Frame n" represents an image at the moment of collision, and "Frame n + 1" represents an image one frame after the moment of collision. The temporal intervals between adjacent frames are equal, about 1 millisecond.
For ease of understanding, only representative frames are shown in FIGS. 8A-8C.

As shown in FIG. 8A, when the length of the bent portion 313 is L2 = 12 mm, the propeller 301 returns to the original position after a time corresponding to Frame n + 234, that is, 0.244 seconds after the collision. It returned to its shape.
On the other hand, as shown in FIG. 8B, when the length of the bent portion 413 is L3 = 18 mm, the propeller 401 takes a time corresponding to Frame n + 328 until it returns to the original shape. That is, it took 0.342 seconds from the collision.
Further, as shown in FIG. 8C, when the length of the bent portion 213 was L1 = 6 mm, the propeller 201 was irreversibly damaged by the collision and did not return to its original shape.

From this result, if the bent portions 213 to 413 are shortened, the time required to return to the original shape after colliding with the obstacle can be shortened, and if the bent portions 213 to 413 are shortened too much, the obstacles can be shortened. It is understood that it becomes vulnerable to. In particular, it is understood that the propeller 301 provided with the bent portion 313 having a length L2 = 12 mm can quickly absorb the impact force received from the obstacle.

FIG. 8D measures the lift generated by the propellers 201 to 401 by changing the rotation speed of the motor M.
At almost all motor M speeds,

propellers

201, 301, and 401 produced the largest lift in that order.

From this result, it is understood that the shorter the bent portion 213 to 413 or the higher the rotation speed of the motor, the larger the lift of the propellers 201 to 401 is generated.

It is understood that it is desirable that the length of the bent portion 13 of the propeller 1 is L2 = 12 mm or more from the viewpoint of achieving both a large lift and resistance to obstacles.

(Fifth experiment)
For a propeller not provided with the deformable edge 14, a simulation experiment was conducted to investigate the lift generated when the length of the bent portion 13 was changed.

As shown in FIGS. 9A, 9B, and 9C, the lengths of the bent portions 513 to 713 of the

propellers

501, 601, and 701 according to the comparative example are L1 = 6 mm, L2 = 12 mm, and L3 = 18 mm, respectively.
Compared to propellers 201-401, propellers 501-701 differ in that they do not have a deformable edge 14.

As shown in FIG. 9D, in the relatively high range of the rotation speed of the motor M from 2000 rpm to 3500 rpm, the simulation result that the magnitude of the lift hardly depends on the lengths L1 to L3 of the bent portions 513 to 713 can be obtained. It was.

As a result, when the rotation speed of the motor M is high, the centrifugal force acting on the propellers 501 to 701 becomes large, and the entire propellers 501 to 701 are supported by the tendon 15 regardless of the shape of the bent portion 513 to 713. It is considered that this is because the shape is stable.

From FIGS. 8D and 9D, when comparing those having the same bent portion lengths L1, L2, and L3, the propellers 501 to 701 are compared with the propellers 201 to 401 at the rotation speeds of almost all the motors M. It is also understood that it produces a large lift.

(Sixth experiment)
An experiment was conducted to compare the case where the propeller 1 has the tendon 15 and the case where the propeller 1 does not have the tendon 15.
As shown in FIG. 10A, the bent portion 813 of the propeller 801 according to the comparative example does not include a tendon.
The bent portion 813 is arranged so as to overlap the hub 11 and the wing portion 12, and the bent portion 813 and the hub 11 and the bent portion 813 and the wing portion 12 are joined to each other.
As shown in the enlarged view of the S portion, the pin 816 is driven in the direction indicated by the arrow in each of the portion of the bent portion 813 that overlaps with the hub 11 and the portion that overlaps with the wing portion 12.

As shown in FIG. 7B, the propeller 301 according to the comparative example is formed in the same shape as the propeller 801. The propeller 301 includes a tendon 15 at the flexion portion 313 as well as the flexion portion 13.

As shown in FIG. 10B, the tip of the wing portion 12 of the propeller 301 is a scale of a ruler arranged parallel to the rotation axis and points to 43.5 mm.
As shown in FIG. 10C, the tip of the wing portion 12 of the propeller 801 is a scale of a ruler arranged parallel to the rotation axis and points to 35.5 mm.

In the stationary state in which the

propellers

301 and 801 are not rotated, the tip of the wing portion 12 of the propeller 801 is 8.0 mm lower than that of the propeller 301.

It is considered that this is because the propeller 801 is more affected by the weight of the wing portion 12 because it does not have the tendon 15.
Therefore, it is understood that the tendon 15 contributes to improving the rigidity of the propeller 1.

11A and 11B are measurements of the magnitude of the force required to deform the tips of the blades 12 of the

propellers

801 and 301 until they reach the same position in a stationary state.

As shown in FIG. 11A, the tip of the wing portion 12 of the propeller 301 was a scale of a ruler arranged parallel to the rotation axis and pointed to 67.0 mm. The magnitude of the force required to push down the tip of the wing portion 12 of the propeller 301 to the reference position by 23.0 mm was 0.120 N.
As shown in FIG. 11B, the tip of the wing portion 12 of the propeller 801 was a scale of a ruler arranged parallel to the rotation axis and pointed to 58.5 mm. The magnitude of the force required to push down the tip of the wing portion 12 of the propeller 801 to the reference position by 16.5 mm was 0.039 N.

From this experiment, the magnitude of the force required to deform the propeller 301 with the tendon 15 to the reference position is about 3 the magnitude of the force required to deform the propeller 801 without the tendon to the same reference position. It is understood to be double.
Therefore, it is understood that the tendon 15 contributes to improving the rigidity of the propeller 1. Further, it is presumed that the material of the bent portion 13, the material and diameter of the tendon 15, the number of tendons 15, and the like affect the rigidity of the propeller 1.

Next, as shown in FIG. 11C, it was obtained that the propeller 801 generated a smaller lift than the propeller 301 in the rotating state.
Further, it was obtained that the difference in the magnitude of the lift generated by the propeller 801 and the propeller 301 increases as the rotation speed of the motor M increases.
Further, at a rotation speed of the motor M exceeding 2000 rpm, the flexion portion 813 of the propeller 801 without the tendon 15 is damaged, so that the measurement itself cannot be performed.
It is considered that these results were obtained because the propeller 801 without the tendon 15 is more strongly affected by the centrifugal force as the rotation speed of the motor M increases as compared with the propeller 301 with the tendon 15. Be done.
Therefore, it is understood that the tendon 15 maintains the shape of the entire propeller 1 at a high rotation speed and contributes to improving the lift of the propeller 1.

11D and 11E compare the magnitude of lift generated by the

propellers

801 and 301 with the simulation.
In the simulation, it was expected that the lift will increase as the rotation speed of the motor M increases. The experimental results are almost in line with the simulation, and as the rotation speed of the motor M increases, the lift generated by the

propellers

801 and 301 also increases.

From this experiment, it was shown that the magnitude of lift generated by propeller 1 was as expected by simulation.

(7th experiment)
An experiment was conducted to investigate the difference in impact force when the drone was flown and the propeller 1 and the conventional propeller 101 were brought into contact with an obstacle.

As shown in FIGS. 12A and 12B, a hard obstacle RO is connected to the tip of the force sensor FS, and

propellers

1 and 101 are attached to the drone DR. The

propellers

1 and 101 were rotated to fly the drone DR and collide with the collision area CA of the obstacle RO, and the impact force applied to the obstacle by the

propellers

1 and 101 was read through the force sensor FS.

As shown in FIG. 12C, both

propellers

1 and 101 applied the maximum impact force to the hard obstacle RO about 3 ms after the moment of collision. The maximum impact force given to the hard obstacle RO by the propeller 1 was about 10 N, and the maximum impact force given to the hard obstacle RO by the propeller 101 was about 67 N.
Further, at almost all the time, the magnitude of the impact force applied to the hard obstacle RO by the propeller 1 did not exceed the magnitude of the impact force applied to the hard obstacle RO by the propeller 101.

From this experiment, it is understood that according to the propeller 1, even if the drone actually flying collides with an obstacle, it is less likely to give an impact force than the conventional propeller 101.

(Second Embodiment)
Propeller 1 has been described as having two blades, but the number of blades is not limited to this.
As shown in FIG. 13, the propeller 21 according to the second embodiment of the present invention has two pairs of four blades in total. The shape of each of these four blades is the same as the blades of the propeller 1, that is, the blade portion 12, the bending portion 13, and the deformable edge 14. Unlike the propeller 1, the four blades are arranged at 90 ° intervals about the rotation axis.
According to the propeller 21, since the area of the blades is larger, vibration during flight can be reduced as compared with the propeller 1 having two blades.

The present invention enables various embodiments and modifications without departing from the broad spirit and scope of the present invention. Moreover, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is indicated not by the embodiment but by the claims. Then, various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of the present invention.

This application is based on Japanese Patent Application No. 2019-198143 filed on October 31, 2019. The specification, claims, and the entire drawing of Japanese Patent Application No. 2019-198143 are incorporated herein by reference.

1, 21, 101, 201, 301, 401, 501, 601, 701, 801 Propeller 11 Hub 12

Wing

13, 213, 313, 413, 513, 613, 713, 813 Flex 14 Deformable Edge 15 Tendon 816 Pin M motor D rotation direction H hole R ring T transition part CA collision area DR drone FS force sensor RO hard obstacle

Claims

In the center and
A blade formed so as to extend outward from the central portion,
A bent portion including a flexible member connecting the central portion and the blade, and a bent portion.
A fiber disposed inside the bent portion and stretched between the central portion and the blade.
propeller.
The blade includes a front edge located on the front side in the direction of rotation.
The front edge is flexible.
The propeller according to claim 1.