Propeller, flying object, and method of manufacturing propeller

Abstract

Provided is a propeller including a plurality of blades which extend radially outward from a central rotary shaft and which have an edge on the opposite side from the central rotary shaft. The blades have a maximum elevation angle, which is the angle at which the elevation of the blades is at a maximum, at a position in the range of 30% to 60% of the radius of a circle centered on the central rotary shaft and passing through the edge of the blades, with the point of origin being the central rotary shaft. The change in the elevation angle along the lengthwise direction of the blades is within 10 degrees per 5% of the radius. The change in the maximum cross-sectional blade thickness, which is the maximum thickness of a cross section of the blades taken in a direction orthogonal to the lengthwise direction, along the lengthwise direction is within 20% of the maximum blade thickness of the blades per 5% of the radius. The change in the chord of the blades along the lengthwise direction is within 20% of the maximum chord of the blades per 5% of the radius.

Description

[Technical Field]

[0001] The present disclosure relates to a propeller, a flying object, and a method for manufacturing a propeller. [Background technology]

[0002] There is a propeller that has multiple blades and rotates around a central axis of rotation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-131038 [Patent Document 2] Japanese Patent Application Publication No. 2019-25957 [Patent Document 3] WO2017 / 146028 publication Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of propeller, stress due to centrifugal force and bending moment acting during rotation tends to concentrate near the central axis of rotation, so it is desirable to improve the strength of the portion of the propeller near the central axis of rotation.

[0005] Therefore, the present disclosure proposes a propeller, a flying object, and a method for manufacturing a propeller that can improve the strength of the portion near the central axis of rotation. [Means for solving the problem]

[0006] A propeller according to the present disclosure has a plurality of blades that extend radially outward from the central axis of rotation with respect to the central axis of rotation and have ends opposite the central axis of rotation, and the blades have a maximum angle of elevation that is the maximum angle of elevation of the blade at a position within a range of 30% to 60% of the radius of a circle that is centered on the central axis of rotation and passes through the end of the blade, with the central axis as the starting point, and the change in the angle of elevation in the longitudinal direction of the blade is within 10 degrees per 5% of the radius, the change in the longitudinal direction of the maximum cross-sectional thickness, which is the maximum thickness of the blade in a cross section perpendicular to the longitudinal direction, is within 20% of the maximum blade thickness of the blade per 5% of the radius, and the change in the chord length of the blade in the longitudinal direction is within 20% of the maximum chord length of the blade per 5% of the radius. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a front view of a flying object according to a first embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view of a propeller according to a first embodiment. [Figure 3] FIG. 2 is a plan view of the propeller according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram for explaining the propeller according to the first embodiment, showing a cross section taken along line IV-IV in FIG. 3. [Figure 5] FIG. 3 is a diagram showing the relationship between the angle of elevation and the position of the propeller according to the first embodiment. [Figure 6] FIG. 3 is a diagram showing the relationship between blade thickness and position in the blade according to the first embodiment. [Figure 7] FIG. 3 is a diagram showing the relationship between the chord length and the position of the blade according to the first embodiment. [Figure 8] 5 is a diagram showing the relationship between thrust and elevation angle and position of a blade according to the first embodiment. FIG. [Figure 9] FIG. 10 is a perspective view of a propeller according to a comparative example. [Figure 10] FIG. 10 is a diagram showing the relationship between the elevation angle and pitch and the position of a blade according to a comparative example. [Figure 11]FIG. 10 is a diagram showing the relationship between thrust, elevation angle, and position in a blade according to a comparative example. [Figure 12] FIG. 4 is a diagram for comparing the angles of elevation of the blades according to the first embodiment and the blades according to the comparative example. [Figure 13] FIG. 10 is a diagram for comparing the thrust generated per power consumption of the blade according to the first embodiment and the blade according to the comparative example. [Figure 14] 3 is a flowchart showing a method for manufacturing a propeller according to the first embodiment. [Figure 15] FIG. 2 is a plan view of a mold used in the method for manufacturing a propeller according to the first embodiment. [Figure 16] FIG. 10 is a perspective view of a propeller propulsion system according to a second embodiment of the present disclosure. [Figure 17] FIG. 10 is a perspective view of a propeller propulsion system according to a first modified example of the second embodiment. [Figure 18] FIG. 10 is a perspective view of a propeller propulsion system according to a second modified example of the second embodiment. [Figure 19] FIG. 10 is a perspective view of a propeller propulsion system according to a third embodiment of the present disclosure, showing the propellers in a deployed state. [Figure 20] FIG. 10 is a perspective view of a propeller propulsion system according to a third embodiment, showing the propeller in a folded state. [Figure 21] FIG. 11 is a perspective view of a propeller propulsion system according to a first modified example of the third embodiment, showing the propeller in an deployed state. [Figure 22] FIG. 11 is a perspective view of a propeller propulsion system according to a first modified example of the third embodiment, showing the propeller in a folded state. [Figure 23] FIG. 11 is a perspective view of a propeller propulsion system according to a second modified example of the third embodiment, showing the propeller in an deployed state. [Figure 24] FIG. 11 is a perspective view of a propeller propulsion system according to a second modified example of the third embodiment, showing the propeller in a folded state. [Figure 25] FIG. 10 is a perspective view of a propeller propulsion system according to a fourth embodiment of the present disclosure, showing the propellers in a deployed state. [Figure 26] FIG. 10 is a perspective view of a propeller propulsion system according to a fourth embodiment, showing the propeller in a folded state. [Figure 27] FIG. 13 is a perspective view of a propeller propulsion system according to a first modified example of the fourth embodiment, showing the propeller in an unfolded state. [Figure 28] FIG. 13 is a perspective view of a propeller propulsion system according to a first modified example of the fourth embodiment, showing the propeller in a folded state. [Figure 29] FIG. 13 is a perspective view of a propeller propulsion system according to a second modified example of the fourth embodiment, showing the propeller in an deployed state. [Figure 30] FIG. 13 is a perspective view of a propeller propulsion system according to a second modified example of the fourth embodiment, showing the propeller in a folded state. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same components are designated by the same reference numerals, and redundant description will be omitted.

[0009] The explanation will be given in the following order: [1. First embodiment] [1-1. Configuration of the flying object according to the first embodiment] [1-2. Propeller] [1-3. Operation] [1-4. Propeller according to comparative example] [1-5. Comparison of the propeller according to the first embodiment with the comparative example] [1-6. Manufacturing method of propeller according to the first embodiment] [1-7.Effects] [2. Second Embodiment] [2-1. Configuration of the propeller propulsion system according to the second embodiment] [2-2. Effects] [2-3. Modifications] 3. Third Embodiment [3-1. Configuration of the propeller propulsion system according to the third embodiment] [3-2. Effects] [3-3. Modifications] [4. Fourth Embodiment] [4-1. Configuration of the propeller propulsion system according to the fourth embodiment] [4-2.Effects] [4-3. Modifications]

[0010] [1. First embodiment] [1-1. Configuration of the flying object according to the first embodiment] FIG. 1 is a front view of a flying object 1 according to the first embodiment of the present disclosure.

[0011] As shown in FIG. 1, the flying object 1 has an airframe 2 and a plurality of (for example, four) propeller propulsion devices 3 supported by the airframe 2. Note that FIG. 1 shows only two of the four propeller propulsion devices 3, 3A and 3B. The flying object 1 is, for example, a drone. Note that the flying object 1 may also be a manned flying object. The number of propeller propulsion devices 3 is not limited to the above.

[0012] The propeller propulsion device 3 has a motor 4 and a propeller 5. The rotor 4a of the motor 4 and the propeller 5 rotate around a central rotation axis C. The position of the central rotation axis C differs for each propeller propulsion device 3. The central rotation axes C of the multiple propeller propulsion devices 3 are, for example, parallel to each other. Of the multiple central rotation axes C, the central rotation axes CA and CB of the propeller propulsion devices 3A and 3B are shown in FIG. 1. The rotor 4a of the motor 4 includes a motor shaft and an iron core. The motor 4 is an outer rotor. However, the motor 4 may be something other than an outer rotor. The motor 4 is an example of a drive source.

[0013] [1-2. Propeller] Fig. 2 is a perspective view of the propeller 5 according to the first preferred embodiment. Fig. 3 is a plan view of the propeller 5 according to the first preferred embodiment. Fig. 4 is an explanatory diagram for explaining the propeller 5 according to the first preferred embodiment, and is a diagram showing a cross section taken along line IV-IV in Fig. 3.

[0014] As shown in Figures 2 and 3, the propeller 5 has a plurality of blades 6A, 6B (two, for example). Hereinafter, blade 6 will be used as a general term to refer to the plurality of blades 6A, 6B. The two blades 6 extend radially outward from the central axis of rotation C with respect to the central axis of rotation C. The two blades 6 extend on opposite sides of the central axis of rotation C. The two blades 6 are formed integrally with each other and constitute a single member (solid). Note that the number of blades 6 is not limited to the above. The number of blades 6 may be three or four, or may be five or more.

[0015] Each blade 6 has a base end 6a on the rotation axis C side and a tip end 6b which is the end opposite the rotation axis C. Each blade 6 also has an upper surface 6c and a lower surface 6d opposite the upper surface 6c. The upper surface 6c and the lower surface 6d are located on opposite sides of each other in the axial direction of the rotation axis C. The upper surface 6c and the lower surface 6d extend between the base end 6a and the tip end 6b. The base ends 6a, the upper surface 6c, and the lower surface 6d of the two blades 6 are connected to each other. The upper surface 6c and the lower surface 6d are each an example of a surface.

[0016] The material of the blades 6 is, for example, a thermoplastic resin such as a carbon fiber reinforced thermoplastic resin or a polyamide resin-based material, etc. However, the material of the blades 6 is not limited to the above.

[0017] FIG. 4 shows the relationship between the angle of elevation α of the blade 6, the chord length L1, and the maximum cross-sectional blade thickness L2. As mentioned above, FIG. 4 shows a cross section taken along line IV-IV in FIG. 3. Here, line IV-IV in FIG. 3 is a line perpendicular to the longitudinal direction (direction D1) of the blade 6 and the axial direction of the central rotation axis C. The angle of elevation α is the inclination angle of the chord L, which is a line connecting the leading end 6e and the trailing end 6f of the blade 6, with respect to the rotation direction R1 (FIG. 3) of the blade 6. In other words, the angle of elevation α is the inclination angle of the chord L with respect to a plane 40 perpendicular to the central rotation axis C. The angle of elevation α is also referred to as the setting angle. The length of the chord L is the chord length L1. The maximum cross-sectional blade thickness L2 is the maximum blade thickness in the cross section of the blade 6 perpendicular to the longitudinal direction. The blade thickness is the thickness of the blade 6 in the direction perpendicular to the chord L. The maximum cross-sectional blade thickness L2 is set closer to the leading end 6e of the leading end 6e or trailing end 6f of the blade 6. As shown in FIG. 3, the propeller radius is the length of a straight line L3 connecting the central axis C of rotation and the point on the blade 6 that is farthest from the central axis C (tip 6b). That is, the propeller radius is the radius of a circle 10 that is centered on the central axis C of rotation and passes through the tip 6b of the blade 6. The propeller radial direction is the direction along the straight line L3. That is, the propeller radial direction is along the direction D1 from the central axis C toward the tip 6b. The longitudinal direction of the blade 6 also runs along the direction D1. The pitch is the distance traveled along the angle of elevation α of the cross section of the blade at a distance r from the central axis C when the propeller 5 rotates once. If the pitch is P, then P = 2πr tan(α).

[0018] FIG. 5 is a diagram showing the relationship between the angle of elevation α and position of the blade 6 according to the first embodiment. FIG. 6 is a diagram showing the relationship between the maximum cross-sectional blade thickness L2 and position of the blade 6 according to the first embodiment. FIG. 7 is a diagram showing the relationship between the chord length L1 and position of the blade 6 according to the first embodiment. FIG. 8 is a diagram showing the relationship between the thrust and the angle of elevation α and position of the blade 6 according to the first embodiment. The position on the horizontal axis (radial position / propeller radius) in FIGS. 5 to 8 is represented by (the distance from the rotation center axis C to the radial (longitudinal) position of the blade 6) / (the distance from the rotation center axis C to the tip 6b of the blade 6). The position (radial position / propeller radius) is also referred to as the propeller blade section.

[0019] 3 and 5, blade 6 has a maximum elevation angle α, which is the maximum elevation angle of blade 6, at position P1, which is in the range of 30% to 60% of the radius of circle 10 that is centered on rotation axis C and passes through tip 6b of blade 6, i.e., the propeller radius, with rotation axis C as the starting point. The maximum elevation angle may be, for example, 40% to 50% of the propeller radius. Note that hereinafter, unless otherwise specified, the radius refers to the radius of circle 10, i.e., the propeller radius.

[0020] Furthermore, as shown in Fig. 5, the change in the elevation angle α in the longitudinal direction of the blade 6 is within 10 degrees per 5% of the radius. In Fig. 5, the range indicated by the arrow indicates that the change in the elevation angle α in the longitudinal direction of the blade 6 is within 10 degrees per 5% of the radius, but over the entire longitudinal area of the blade 6, the change in the elevation angle α in the longitudinal direction of the blade 6 is within 10 degrees per 5% of the radius.

[0021] 6, the change in the maximum cross-sectional thickness L2 of the blade 6 in the longitudinal direction of the blade 6 is within 20% of the maximum thickness of the blade 6 per 5% of the radius. The maximum thickness of the blade is, in other words, the largest thickness among the maximum cross-sectional thicknesses L2 of the blade 6, and is the maximum thickness of the entire blade 6. In FIG. 6, the range indicated by the arrows indicates that the change in the maximum cross-sectional thickness L2 of the blade 6 in the longitudinal direction of the blade 6 is within 20% of the maximum thickness of the blade 6 per 5% of the radius, and over the entire longitudinal region of the blade 6, the change in the maximum cross-sectional thickness L2 of the blade 6 in the longitudinal direction is within 20% of the maximum thickness of the blade 6 per 5% of the radius.

[0022] 7, the change in the chord length L1 of the blade 6 in the longitudinal direction of the blade 6 is within 20% of the maximum chord length L1 of the blade 6 per 5% of the radius. The maximum chord length L1 of the blade 6 is, in other words, the maximum chord length of the entire blade 6. In FIG. 7, the range indicated by the arrows indicates that the change in the chord length L1 of the blade 6 in the longitudinal direction of the blade 6 is within 20% of the maximum chord length L1 of the blade 6 per 5% of the radius, but over the entire longitudinal direction of the blade 6, the change in the chord length L1 of the blade 6 in the longitudinal direction of the blade 6 is within 20% of the maximum chord length L1 of the blade 6 per 5% of the radius.

[0023] As shown in Figures 3 and 5, the upper surface 6c and the lower surface 6d each have flat areas 6ca and 6cb that are perpendicular to the axial direction of the rotation axis C within 10% of the radius starting from the rotation axis C.

[0024] [1-4. Operation] In the flying object 1 configured as described above, thrust is generated by the rotation of the propeller 5 driven by the motor 4. Here, Fig. 8 is a diagram showing the relationship between the thrust and the elevation angle α and the position of the blade 6 according to the first embodiment. When the propeller 5 rotates, thrust as shown in Fig. 8 is generated according to the radial position, which is the radial position (longitudinal position) of the blade 6.

[0025] [1-5. Propeller according to comparative example] Fig. 9 is a perspective view of a propeller 105 according to a comparative example. Fig. 10 is a diagram showing the relationship between the elevation angle α and pitch and position of a blade 106 according to a comparative example. Fig. 11 is a diagram showing the relationship between the thrust, elevation angle α and position of a blade 106 according to a comparative example.

[0026] As shown in FIG. 9, the propeller 105 of the comparative example has two blades 106A and 106B. Hereinafter, the term "blade 106" will be used to collectively refer to the multiple blades 106A and 106B. The two blades 106 extend radially outward from the rotation axis 100C. The two blades 106 extend on opposite sides of the rotation axis 100C. The two blades 106 are integrally formed with each other to form a single member (solid). Furthermore, the blade 6 of the propeller 105 of the comparative example has the elevation angle and pitch shown in FIG. 10. Furthermore, FIG. 11 shows the thrust distribution of the blade 106 of the comparative example. In the comparative example, approximately 85% of the thrust is generated radially outward from the rotation axis 100C, starting from 40% of the propeller radius. Here, the larger the angle of elevation of a fixed wing, the greater the thrust generated, but the propeller 105, which is a rotating wing, moves slower in the direction of rotation the closer it is to the central axis of rotation. Since the thrust generated by the propeller 105 is proportional to the square of the moving speed, not much thrust is generated near the root of the propeller 105 (the part including the base end) despite the large angle of elevation.

[0027] While propellers for small- to medium-sized unmanned aircraft, such as the comparative example propeller 105, are sometimes made of carbon fiber, they are often made of resin-molded components based on cost-effective materials such as plastic or nylon. The stresses caused by centrifugal force and bending moment acting on the propeller during rotation are concentrated near the propeller's central axis of rotation. Therefore, strengthening the rigidity of the blade root (base end) is desirable. Conventional propellers, however, have aerofoil shapes with large angles of attack to generate thrust near the root. Generally, it is difficult to increase rigidity in a shape designed for aerodynamic efficiency, which limits the propeller's upper limit for rotational speed. Therefore, when greater thrust is required, the only options are to either increase the propeller diameter to achieve high power output even at low rotation speeds, or to change the propeller material itself to a more rigid one.

[0028] [1-6. Comparison of the propeller according to the first embodiment with a comparative example] Fig. 12 is a diagram for comparing the angle of elevation of the blade 6 according to the first embodiment and the blade 106 according to the comparative example. Fig. 13 is a diagram for comparing the thrust generated per power consumption of the blade 6 according to the first embodiment and the blade 106 according to the comparative example.

[0029] As shown in FIG. 12 , the blade 6 of this embodiment and the blade 106 of the comparative example have different angles of elevation. As can be seen from FIG. 12 , the maximum angle of elevation of the blade 6 of this embodiment is located radially outward from the rotation center axis C relative to the maximum angle of elevation of the blade 106 of the comparative example. The angle of elevation of the blade 6 gradually decreases from the position P1 of the maximum angle of elevation toward the rotation center axis C. At this time, the maximum cross-sectional blade thickness L2 of the blade 6 gradually increases from the position P1 of the maximum angle of elevation toward the rotation center axis C. This shape was adopted because the cross-sectional shape of the portion of the blade 6 closer to the rotation center axis C than the maximum angle of elevation does not necessarily need to be a blade shape that takes aerodynamic efficiency into consideration. Therefore, a shape that prioritizes strengthening bending resistance is used to avoid discontinuous shapes that are prone to stress concentration. On the other hand, the blade 106 of the comparative example has a portion where the cross section perpendicular to the longitudinal direction changes abruptly in the longitudinal direction, and stress is likely to concentrate there. In contrast, the blade 106 of this embodiment has the above-described shape, so the cross section does not change abruptly in the longitudinal direction. That is, the blade 6 of this embodiment has a shape that is continuous in the longitudinal direction. While the blades of a typical propeller are designed so that the angle of elevation increases from the tip to the base end of the blade to maintain a constant pitch, the blade 6 of this embodiment achieves the above-described shape by intentionally not maintaining a constant pitch. This shape of the blade 6 can suppress stress concentration in the blade 6. Furthermore, as shown in FIG. 13 , the blade 6 of this embodiment and the blade 106 of the comparative example generate substantially the same thrust per unit of power consumption overall. That is, the blade 6 of this embodiment suppresses a decrease in the thrust generation efficiency of the entire propeller 5, while improving the rigidity and therefore strength of the root portion (the portion including the base end 6 a) that receives the most load. Furthermore, this shape of the blade 106 improves transfer accuracy in the injection molding process described next.

[0030] Furthermore, when an axial force is applied to the tip 6b of the blade 6 of this embodiment, the amount of deflection of the tip 6b is 20% less than that of the blade 106 of the comparative example. Specifically, the rigidity and therefore the strength of the blade 6 of this embodiment are increased by more than 20% compared to the blade 106 of the comparative example. Furthermore, the resonant frequency of the blade 6 of this embodiment is 20% higher than that of the blade 106 of the comparative example. This allows the blade 6 to rotate at a higher speed than the blade 106 of the comparative example. This makes it easier to move the resonant frequency outside the operating rotational speed range of the propeller 5. Note that even if the resonant mode of a conventional propeller such as the propeller 104 of the comparative example can be moved outside the operating rotational speed range of the propeller, internal stresses due to bending and torsional moments still concentrate at the root of the blade. Therefore, it is desirable to increase the rigidity and strength of the root portion of the propeller.

[0031] [1-7. Manufacturing method of propeller according to the first embodiment] Fig. 14 is a flowchart showing a method for manufacturing the propeller 5 according to the first embodiment. Fig. 15 is a plan view of a mold 50 used in the method for manufacturing the propeller 5 according to the first embodiment.

[0032] As shown in FIG. 14, an injection process is performed by an injection molding machine (S1). The injection molding machine has a mold 50 shown in FIG. 15. The mold 50 is used to form the propeller 5 (blades 6). The mold 50 has a lower mold 51 and an upper mold 52 that is placed on top of the lower mold 51. A cavity 53 is provided between the lower mold 51 and the upper mold 52. The upper mold 52 also has a gate 54 that communicates with the cavity 53. The gate communicates with the center of the cavity 53. In other words, the gate 54 faces the center of the propeller 5 to be formed. The injection molding machine injects molten material from the gate 54 into the cavity 53 of the mold 50, filling the cavity 53 with the material. At this time, the material flows from the center of the cavity 53 toward the edges. Because the cavity 53 conforms to the shape of the propeller 5 to be manufactured, the material has good fluidity, suppressing backflow of the material within the cavity 53. Here, for example, in the case of a conventional mold for manufacturing the comparative example propeller 105, the cavity has a complex shape, resulting in low fluidity. To suppress backflow of the material and fill the entire cavity with the material using a conventional mold, it is necessary to raise the mold temperature before injecting the material. However, this increases the material's shrinkage rate after cooling, resulting in poor transferability. Furthermore, propellers manufactured using conventional molds also have high internal residual stress, necessitating an annealing process. However, this also deforms the propeller from its designed shape, further degrading transferability. In contrast, the mold 50 of this embodiment has good fluidity and good transferability, reducing or eliminating the need to increase the mold 50 temperature or perform an annealing process. The material is a thermoplastic resin, such as the carbon fiber-reinforced thermoplastic resin or polyamide resin-based material described above.

[0033] If the material of the propeller 5 is a carbon fiber reinforced thermoplastic resin or a polyamide resin-based material, the strength can be improved, but friction with the mold 50 tends to increase. For this reason, in the case of a conventional mold for manufacturing the propeller 105 of the comparative example, for example, the durability of the mold deteriorates, resulting in increased manufacturing costs. In contrast, the mold 50 of the present embodiment has good material fluidity, making it easier to reduce friction between the material and the mold 50 compared to conventional molds. This improves mold durability, resulting in reduced manufacturing costs.

[0034] 14, a worker, a removal device, or other such worker separates lower mold 51 and upper mold 52 and removes the solidified material from mold 50 (S2). Next, a worker, a processing device, or other such worker removes the portion of the solidified material other than propeller 5, for example, the portion formed by gate 54. In this manner, propeller 5 is manufactured.

[0035] [1-8.Effects] As described above, the propeller 5 of this embodiment has a plurality of blades 6. The blades 6 extend radially outward relative to the central axis of rotation C. The blades 6 have tips 6b (ends) on the opposite side from the central axis of rotation. The blades 6 have a maximum elevation angle α at a position within a range of 30% to 60% of the radius of a circle 10 that is centered on the central axis of rotation C and passes through the tips 6b of the blades 6, with the central axis of rotation C as the starting point. The change in the elevation angle α in the longitudinal direction of the blades 6 is within 10 degrees per 5% of the radius. The change in the longitudinal direction of the maximum cross-sectional thickness L2, which is the maximum thickness of the blades 6 in a cross section perpendicular to the longitudinal direction of the blades 6, is within 20% of the maximum blade thickness of the blades 6 per 5% of the radius. The change in the longitudinal chord length L1 of the blades 6 is within 20% of the maximum chord length L1 of the blades 6 per 5% of the radius.

[0036] This configuration improves the strength of the portion of the propeller 5 near the central axis C of rotation. If the strength is insufficient, the propeller will vibrate during rotation, which can increase wind noise. In contrast, the propeller 5 of this embodiment has a relatively high strength, which can suppress vibrations in the propeller 5 and reduce wind noise. Furthermore, the relatively high strength of the propeller 5 makes it easy to increase the resonant frequency of the propeller 5, which makes it easy to increase the rotational speed of the propeller 5 while suppressing resonance. Furthermore, this can improve transfer accuracy when the propeller 5 is injection molded.

[0037] In this embodiment, the number of blades 6 is any one of two to four, and a plurality of blades 6 are integrally formed with one another to form one member.

[0038] With this configuration, the number of parts of the propeller 5 can be easily reduced.

[0039] In addition, in this embodiment, the blade 6 has a maximum chord length L1 either within 10% of the radius on the rotation axis C side or within 10% of the radius on the opposite side of the rotation axis C from the position of the maximum elevation angle on the blade 6.

[0040] With this configuration, the strength of the portion in the vicinity of the central axis of rotation C of the propeller 5 can be further improved.

[0041] In this embodiment, the blade 6 has an upper surface 6c and a lower surface 6d (surfaces) located on opposite sides of the axial direction of the rotation center axis C. The upper surface 6c and the lower surface 6d each have flat areas 6ca, 6cb that are perpendicular to the axial direction of the rotation center axis C within 10% of the radius from the rotation center axis C.

[0042] With this configuration, the strength of the portion in the vicinity of the central axis of rotation C of the propeller 5 can be further improved.

[0043] In this embodiment, the material of the blades 6 is a thermoplastic resin. As an example, the thermoplastic resin is a carbon fiber reinforced thermoplastic resin. As another example, the thermoplastic resin is a polyamide resin-based material.

[0044] According to this configuration, the blades 6 can be manufactured by injection molding.

[0045] Furthermore, the flying object 1 of this embodiment has a propeller 5 and a motor 4 (drive source) that drives the propeller 5.

[0046] With this configuration, it is possible to obtain a flying object 1 with improved strength in the portion near the central axis of rotation C of the propeller 5.

[0047] In addition, the manufacturing method of the propeller 5 of this embodiment includes an injection process of injecting molten material into a mold 50 for forming the blades 6 of the propeller 5, and a removal process of removing the solidified material from the mold 50.

[0048] According to this configuration, a propeller 5 having improved strength in the portion near the central axis of rotation C can be manufactured.

[0049] [2. Second Embodiment] [2-1. Configuration of the propeller propulsion system according to the second embodiment] FIG. 16 is a perspective view of a propeller propulsion system 203 according to the second embodiment of the present disclosure.

[0050] As shown in Figure 16, a propeller propulsion system 203 of this embodiment has a motor 204 and a propeller 205 instead of the motor 4 and the propeller 5. The propeller 205 is directly fixed to the motor 204 by a fastener 210 such as a screw. The motor 204 differs from the motor 4 in that the rotor 204a is provided with two female threads (not shown) to which the fastener 210 is fastened, but other parts are the same as the motor 4. Specifically, the rotor 204a has a cylindrical portion 204b and a mounting wall 204c that covers an opening at one end of the cylindrical portion 204b, and the mounting wall 204c is provided with female threads.

[0051] Propeller 205 has two blades 206A and 206B. Hereinafter, blade 206 will be used as a general term for blades 206A and 206B. Blade 206 differs from blade 6 in that it is provided with a through-hole (not shown) into which fastener 210 is inserted, but other parts are the same as blade 6. Propeller 205, like propeller 5, is manufactured by injection molding.

[0052] [2-3. Effects] As described above, in this embodiment, the blades 6 are fixed to the motor 204 by the fasteners 210 such as screws, so that the blades 6 can be easily replaced.

[0053] [2-4. Modifications] Fig. 17 is a perspective view of a propeller propulsion system 303 according to a first modified example of the second embodiment. As shown in Fig. 17, the propeller propulsion system 303 has a motor 304 and a propeller 305 instead of the motor 204 and the propeller 205. The propeller 305 is directly fixed to the motor 304 by a fastener 210 such as a screw. The motor 304 differs from the motor 204 in that a mounting wall 304c of the rotor 304a is provided with three female threads (not shown) to which the fasteners 210 are fastened, but other parts are the same as the motor 204.

[0054] Propeller 305 has three blades 306A, 306B, and 306C and connecting portion 307. Hereinafter, blade 306 will be used as a general term for blades 306A, 306B, and 306C. The three blades 306 differ from blade 206 in that base ends 6a are connected to each other by connecting portion 307, but are otherwise similar to blade 206. Propeller 305 is manufactured by injection molding, similar to propeller 5.

[0055] Fig. 18 is a perspective view of a propeller propulsion system 403 according to a second modification of the second embodiment. As shown in Fig. 18, the propeller propulsion system 403 has a motor 404 and a propeller 405 instead of the motor 204 and the propeller 205. The propeller 405 is directly fixed to the motor 404 by a fastener 210 such as a screw. The motor 404 differs from the motor 204 in that a mounting wall 404c of the rotor 404a is provided with four female threads (not shown) to which the fasteners 210 are fastened, but other parts are the same as the motor 204.

[0056] Propeller 405 has four blades 406A, 406B, and 406C and a connecting portion 407. Hereinafter, blade 406 will be used as a general term for blades 406A, 406B, and 406C. The four blades 406 differ from blade 206 in that base ends 6a are connected to each other by connecting portion 407, but are otherwise similar to blade 206. Propeller 405 is manufactured by injection molding, similar to propeller 5.

[0057] Since the number of blades 306, 406 of propellers 305, 405 in each of the above comparative examples is greater than the number of blades 206 of propeller 205, propellers 305, 405 can obtain higher output at lower rotation speeds than propeller 205. On the other hand, the number of blades 206 of propeller 205 is less than the number of blades 306, 406 of propellers 305, 405, so propeller 205 has higher thrust generation efficiency than propellers 305, 405.

[0058] 3. Third Embodiment [3-1. Configuration of the propeller propulsion system according to the third embodiment] Fig. 19 is a perspective view of a propeller propulsion system 503 according to a third embodiment of the present disclosure, with a propeller 505 in an unfolded state. Fig. 20 is a perspective view of a propeller propulsion system 503 according to the third embodiment, with a propeller 505 in a folded state.

[0059] As shown in Fig. 19, a propeller propulsion system 503 of this embodiment has a motor 504 and a propeller 505 instead of the motor 4 and the propeller 5. Blades 506A and 506B of the propeller 505 are directly fixed to the motor 504 by fasteners 210 such as screws. The motor 504 differs from the motor 4 in that the rotor 504a is provided with two female threads (not shown) to which the fasteners 210 are fastened, but other parts are the same as the motor 4. Specifically, the rotor 504a has a cylindrical portion 204b and a mounting wall 504c that covers an opening at one end of the cylindrical portion 204b, and the mounting wall 504c is provided with female threads.

[0060] Propeller 505 has two blades 506A and 506B. Hereinafter, blade 506 will be used as a general term for blades 506A and 506B. The two blades 506 are formed separately from each other and are connected to each other by mounting wall 504c serving as a connecting member, and differ from blade 6 in that they are provided with a through-hole (not shown) into which coupling device 210 is inserted, but are otherwise similar to blade 6. Each blade 506 is manufactured by injection molding, similar to propeller 5. Mounting wall 504c is also referred to as a mounting portion.

[0061] The blades 506 are provided rotatably around the connector 210 between an operating position (FIG. 19) where they generate thrust when the propeller 505 rotates, and a folded position (FIG. 20).

[0062] [3-3. Effects] As described above, in this embodiment, the blades 6 are provided rotatably between the operating position (FIG. 19) and the folded position (FIG. 20), so that the propeller 505 can be put into the folded state (FIG. 20).

[0063] [3-4. Modifications] Fig. 21 is a perspective view of a propeller propulsion system 603 according to a first modified example of the third embodiment, with the propeller 605 in an unfolded state. Fig. 22 is a perspective view of a propeller propulsion system 603 according to a first modified example of the third embodiment, with the propeller 605 in a folded state.

[0064] 21, the propeller propulsion system 603 has a motor 604 and a propeller 605 instead of the motor 504 and the propeller 505. The motor 604 differs from the motor 504 in that a mounting wall 604c of the rotor 604a is provided with three female screw portions (not shown) to which the coupling 210 is coupled, but other parts are the same as the motor 504.

[0065] Propeller 605 differs from propeller 505 in that it has three blades 606A, 606B, and 606C, but is otherwise similar to propeller 505. Hereinafter, blade 606 will be used as a general term for blades 606A, 606B, and 606C. Blade 606 is provided rotatably around connector 210 between an operating position (FIG. 21) where thrust is generated when propeller 605 rotates, and a folded position (FIG. 22). Each blade 606 is manufactured by injection molding, similar to propeller 5.

[0066] Fig. 23 is a perspective view of a propeller propulsion system 703 according to a second modified example of the third embodiment, showing a state in which the propeller 705 is unfolded. Fig. 24 is a perspective view of a propeller propulsion system 703 according to a second modified example of the third embodiment, showing a state in which the propeller 705 is folded.

[0067] 23, propeller propulsion system 703 has a motor 704 and a propeller 705 instead of motor 504 and propeller 505. Motor 704 differs from motor 504 in that a mounting wall 704c of rotor 704a is provided with four female screw portions (not shown) to which coupling device 210 is coupled, but other parts are the same as motor 504.

[0068] Propeller 705 differs from propeller 505 in that it has four blades 706A, 706B, 706C, and 706D, but is otherwise similar to propeller 505. Hereinafter, blade 706 will be used as a general term for blades 706A, 706B, 706C, and 706D. Blade 706 is provided rotatably around connector 210 between an operating position (FIG. 23) where thrust is generated when propeller 705 rotates and a folded position (FIG. 24). Each blade 706 is manufactured by injection molding, similar to propeller 5.

[0069] According to the above-described blades 506, 606, 706, the number of blades 506, 606, 706 can be changed by changing the mounting walls 504c, 604c, 704c without changing the shape of the blades 506, 606, 706.

[0070] [4. Fourth Embodiment] [4-1. Configuration of the propeller propulsion system according to the fourth embodiment] Fig. 25 is a perspective view of a propeller propulsion system 803 according to a third embodiment of the present disclosure, with a propeller 805 in an unfolded state. Fig. 26 is a perspective view of a propeller propulsion system 803 according to the third embodiment, with a propeller 805 in a folded state.

[0071] As shown in Figure 25, a propeller propulsion system 803 of this embodiment has a motor 204 and a propeller 805 instead of the motor 4 and the propeller 5. The propeller propulsion system 803 also has a hub 808 that connects blades 506A, 506B of the propeller 805 to the motor 204. The hub 808 extends linearly in a direction perpendicular to the central axis of rotation C, and supports the blades 506 at both ends. The hub 808 is included in the propeller 805. The hub 808 is an example of a connecting member.

[0072] The propeller 805 has two blades 506A and 506B as described in the third embodiment (FIG. 19). The blades 506 are coupled to the motor 204 via the hub 808 by a coupling 210, with the base end 6a of each blade fitted into a recess 808a of the hub 808. The blades 506 are rotatable around the coupling 210 between an operating position (FIG. 25) where they generate thrust when the propeller 805 rotates, and a folded position (FIG. 26).

[0073] [4-3. Effects] As described above, in this embodiment, the blades 6 are provided rotatably between the operating position (FIG. 19) and the folded position (FIG. 25), so that the propeller 805 can be put into the folded state (FIG. 26).

[0074] [4-4. Modifications] Fig. 27 is a perspective view of a propeller propulsion system 903 according to a first modified example of the fourth embodiment of the present disclosure, with the propeller 905 in an unfolded state. Fig. 28 is a perspective view of a propeller propulsion system 903 according to a first modified example of the fourth embodiment, with the propeller 905 in a folded state.

[0075] As shown in FIG. 27, the propeller propulsion system 903 has a motor 304 and a propeller 905 instead of the motor 204 and the propeller 805 .

[0076] Propeller 905 differs from propeller 805 described in the first modified example of the third embodiment (FIG. 21) in that it has three blades 606A, 606B, and 606C and a hub 908, but other parts are similar to propeller 805. Hub 908 has three arm portions 908b extending radially from central axis of rotation C, and supports blades 606 at the tip of each arm portion 908b. Blades 606 are provided rotatably around coupling 210 between an operating position (FIG. 27) where they generate thrust when propeller 905 rotates and a folded position (FIG. 28).

[0077] Fig. 29 is a perspective view of a propeller propulsion system 1003 according to a second modified example of the fourth embodiment, with the propeller 1005 in an unfolded state. Fig. 30 is a perspective view of a propeller propulsion system 1003 according to a second modified example of the fourth embodiment, with the propeller 1005 in a folded state.

[0078] As shown in FIG. 29, the propeller propulsion system 1003 has a motor 404 and a propeller 1005 instead of the motor 804 and the propeller 805 .

[0079] Propeller 1005 differs from propeller 805 in that it has four blades 706A, 706B, 706C, and 706D and a hub 1008, but other parts are similar to propeller 805. Hub 1008 has four arms 1008b extending radially from a central axis of rotation C, and supports blades 706 at the tip of each arm 1008b. Blades 706 are rotatable about coupling 210 between an operating position (FIG. 29) that generates thrust when propeller 1005 rotates and a folded position (FIG. 30).

[0080] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0081] The present technology can also be configured as follows. (1) a plurality of blades extending radially outward from the rotation center axis and having ends opposite to the rotation center axis; the blade has a maximum elevation angle that is the maximum elevation angle of the blade at a position within a range of 30% to 60% of the radius of a circle that is centered on the central axis of rotation and passes through the end of the blade, with the central axis of rotation as the starting point, The change in the elevation angle in the longitudinal direction of the blade is within 10 degrees per 5% of the radius, A change in the longitudinal direction of a maximum cross-sectional thickness, which is the maximum thickness in a cross section of the blade perpendicular to the longitudinal direction, is within 20% of the maximum thickness of the blade per 5% of the radius, The change in the chord length of the blade in the longitudinal direction is within 20% of the maximum chord length of the blade per 5% of the radius. propeller. (2) The plurality of sheets is any one of 2 to 4 sheets, The propeller according to (1), wherein the plurality of blades are integrally formed to form a single member. (3) The plurality of sheets is any one of 2 to 4 sheets, The propeller according to (1), wherein the plurality of blades are formed separately from one another and connected to one another by a connecting member. (4) A propeller according to any one of (1) to (3), wherein the blade has a maximum chord length within 10% of the radius on the side of the rotation axis relative to the position of the maximum angle of elevation on the blade, or within 10% of the radius on the side opposite the rotation axis. (5) the blade has two surfaces positioned opposite to each other in the axial direction of the central rotation shaft, A propeller described in any one of (1) to (4), wherein the two surfaces each have a flat area perpendicular to the axial direction of the rotation center axis within 10% of the radius starting from the rotation center axis. (6) The propeller according to any one of (1) to (5), wherein the material of the blades is a thermoplastic resin. (7) The propeller according to (6), wherein the thermoplastic resin is a carbon fiber reinforced thermoplastic resin. (8) The propeller according to (6), wherein the thermoplastic resin is a polyamide resin-based material. (9) A propeller according to any one of (1) to (8), a drive source that drives the propeller; A flying object having: (10) an injection step of injecting a molten material into a mold for forming the propeller blades, the propeller blades having a plurality of blades extending radially outward from the central axis of rotation with an end opposite to the central axis of rotation, the blades having a maximum angle of elevation at a position within a range of 30% to 60% of the radius of a circle centered on the central axis of rotation and passing through the end of the blade, the angle of elevation of the blade in the longitudinal direction being within 10 degrees per 5% of the radius, the maximum cross-sectional thickness of the blade, which is the maximum thickness of the blade in a cross section perpendicular to the longitudinal direction, being within 20% of the maximum blade thickness of the blade per 5% of the radius, and the chord length of the blade being within 20% of the maximum chord length of the blade per 5% of the radius; a removal step of removing the solidified material from the mold; A method for manufacturing a propeller, comprising: (11) The plurality of sheets is any one of 2 to 4 sheets, The method for manufacturing a propeller according to (10), wherein the plurality of blades are integrally formed to form a single member. (12) The plurality of sheets is any one of 2 to 4 sheets, The method for manufacturing a propeller according to (10), wherein the plurality of blades are formed separately from one another and connected to one another by a connecting member. (13) The method for manufacturing a propeller according to any one of (10) to (12), wherein the blade has a maximum chord length within 10% of the radius on the side of the rotation axis relative to the position of the maximum angle of elevation on the blade, or within 10% of the radius on the side opposite to the rotation axis. (14) the blade has two surfaces positioned opposite to each other in the axial direction of the central rotation shaft, A method for manufacturing a propeller according to any one of (10) to (13), wherein the two surfaces each have a flat area perpendicular to the axial direction of the central axis of rotation within 10% of the radius starting from the central axis of rotation. (15) The method for manufacturing a propeller according to any one of (10) to (14), wherein the material of the blades is a thermoplastic resin. (16) The method for manufacturing a propeller according to (15), wherein the thermoplastic resin is a carbon fiber reinforced thermoplastic resin. (17) The method for manufacturing a propeller according to (15), wherein the thermoplastic resin is a polyamide resin-based material. [Explanation of symbols]

[0082] 1...Flying object 4,204,304,404,504,604,704...Motor (drive source) 5,205,305,405,505,605,705,805,905,1005,…Propeller 6,206,306,406,506,606,706...Feathers 6b…Tip (end) 808, 908, 1008...Hub (connecting member) C: Rotation axis L1…Chord length L2…Maximum cross-sectional blade thickness S1…Injection process S2…Removal process α…elevation angle

Claims

1. a plurality of blades extending radially outward from the rotation center axis and having ends opposite to the rotation center axis; the blade has a maximum elevation angle that is the maximum elevation angle of the blade at a position in a range of 30% to 60% of the radius of a circle that is centered on the central axis of rotation and passes through the end of the blade, with the central axis of rotation as the starting point, The change in the angle of elevation in the longitudinal direction of the blade is within 10 degrees per 5% of the radius, a change in the longitudinal direction of a maximum cross-sectional thickness, which is the maximum thickness in a cross section of the blade perpendicular to the longitudinal direction, is within 20% of the maximum thickness of the blade per 5% of the radius; a change in the chord length of the blade in the longitudinal direction is within 20% of the maximum chord length of the blade per 5% of the radius; propeller.

2. The plurality of sheets is any one of two to four sheets, 2. The propeller according to claim 1, wherein the plurality of blades are integrally formed with one another to form a single member.

3. The plurality of sheets is any one of two to four sheets, 2. The propeller according to claim 1, wherein the plurality of blades are formed separately from one another and connected to one another by a connecting member.

4. 2. The propeller of claim 1, wherein the blade has a maximum chord length within 10% of the radius on the side of the rotation axis relative to the position of the maximum angle of attack on the blade, or within 10% of the radius on the side of the rotation axis opposite the position of the radius on the blade.

5. The plurality of sheets is any one of two to four sheets, 5. The propeller according to claim 4, wherein the plurality of blades are integrally formed to form a single member.

6. The plurality of sheets is any one of two to four sheets, 5. The propeller according to claim 4, wherein the plurality of blades are formed separately from one another and connected to one another by a connecting member.

7. the blade has two surfaces positioned opposite to each other in the axial direction of the central rotation shaft, 5. The propeller according to claim 4, wherein each of the two surfaces has a flat area perpendicular to the axial direction of the central rotation axis within 10% of the radius from the central rotation axis.

8. The plurality of sheets is any one of two to four sheets, 8. The propeller according to claim 7, wherein the plurality of blades are integrally formed with one another to form a single member.

9. The plurality of sheets is any one of two to four sheets, 8. The propeller according to claim 7, wherein the plurality of blades are formed separately from one another and connected to one another by a connecting member.

10. 10. The propeller of claim 1, wherein the blade material is a thermoplastic resin.

11. 11. The propeller of claim 10, wherein the thermoplastic resin is a carbon fiber reinforced thermoplastic resin.

12. 11. The propeller of claim 10, wherein the thermoplastic resin is a polyamide resin-based material.

13. The propeller of claim 1; a drive source that drives the propeller; A flying object having:

14. an injection step of injecting a molten material into a mold for forming the blades of a propeller having a plurality of blades extending radially outward from a central axis of rotation with respect to the central axis of rotation and having an end opposite to the central axis of rotation, the blades having a maximum angle of elevation at a position within a range of 30% to 60% of the radius of a circle centered on the central axis of rotation and passing through the end of the blade, the angle of elevation in the longitudinal direction of the blade varying within 10 degrees per 5% of the radius, the maximum cross-sectional thickness, which is the maximum thickness of the blade in a cross section perpendicular to the longitudinal direction, varying within 20% of the maximum blade thickness of the blade per 5% of the radius, and the chord length of the blade varying within 20% of the maximum chord length of the blade per 5% of the radius; a removal step of removing the solidified material from the mold; A method for manufacturing a propeller, comprising:

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