JP4402160B1 - Model rotorcraft rotor blade and method of manufacturing the rotor - Google Patents

Abstract

The present invention provides a rotary wing that can be applied to a model rotary wing aircraft and has realism close to that of an actual aircraft, and a method of manufacturing the rotary wing.
A cylindrical aluminum alloy tube 10 having a desired length is formed by roll forming so that a cross-section thereof becomes a blade cross-sectional shape. Thereby, the rotary wing 5a for model rotary wing aircraft can be configured in a hollow structure. For this reason, the weight of the rotary blade 5a is greatly reduced. According to such a rotary blade 5a, a weight problem and a heavy feeling peculiar to an aluminum alloy (metal peculiar) can be brought out, and a problem of weight around a metal material can be avoided. In addition, the rotor blade 5a has a single-layer structure (integrated structure) by molding the aluminum alloy tube 10, and has sufficient strength.
[Selection] Figure 3

Description

  The present invention relates to a rotor of a model rotorcraft and a method for manufacturing the rotor.

Conventionally, as a rotary wing aircraft, for example, there are a helicopter, a gyroplane, an autogyro, a gyrodyne, and the like.
In particular, as a typical model rotary wing aircraft, there is a radio control helicopter, for example.

  A radio-controlled helicopter is equipped with a drive source (for example, an engine) in the same manner as an actual (full-scale) helicopter, and flies into the air by the driving force of the drive source and its behavior is controlled. More specifically, it has a main rotor blade for levitating the airframe and a tail rotor blade for controlling the airframe to rotate in the reverse direction due to the reaction of the rotational force of the main rotor blade, and at least its main rotation Control of flight and behavior is realized by controlling the rotation of the wing and the tail rotor (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 06-091059

  As described above, the radio-controlled helicopter as a representative example of a model rotary wing aircraft has no difference in operating principle from the actual helicopter. For example, enthusiasts of radio-controlled helicopters have the same realism ( For example, a heavy feeling or a heavy feeling) is often required.

However, the radio control helicopter may be smaller in size than the actual helicopter, and the realism is inevitably inferior.
In addition, it is necessary to use a lighter material for the radio control helicopter, and a material used for an actual helicopter cannot always be used for the radio control helicopter. This point is also considered to be a cause of loss of realism in radio controlled helicopters.

  For example, as rotary blades for radio control helicopters, those made of carbon fiber, glass fiber, or wood (balsa material) are mainly used. Since such a material is lightweight and has high strength, it is suitable as a material for a rotor blade of a radio control helicopter. In addition, it is suitable not only as a material for a rotary wing of a radio control helicopter but also as a material for a wing in general model aircraft (for example, a radio control airplane).

  On the other hand, if the rotor blades of a radio control helicopter are made of materials such as carbon fiber, glass fiber, or wood (balsa wood), the realism close to that of the actual helicopter may not be exhibited. The request was not satisfied.

  The present invention has been made in view of these problems, and is intended to provide a rotor that can be applied to a model rotorcraft and has realism closer to that of an actual aircraft, and a method for manufacturing the rotor.

The rotary wing (rotary wing of a model rotary wing aircraft) according to the first invention of the present application, which has been made to achieve the above object, is a slender cylindrical aluminum alloy pipe having a desired size, which is used to feed out the aluminum alloy pipe. The aluminum alloy tube is fed by pressure from two opposite directions and roll-formed, and the aluminum alloy tube has a blade cross-sectional shape as viewed from one end in the longitudinal direction and is integral with the inside. in which the hollow structure is the roll forming so as to form. For example, in a radio controlled helicopter, the rotor blade can be used as a main rotor blade (main rotor blade) or a tail rotor blade (tail rotor blade).

  An aluminum alloy is an alloy mainly composed of aluminum. Aluminum itself is a light but soft metal. For example, it becomes a metal material (aluminum alloy) having high strength by alloying with copper, manganese, silicon, magnesium, zinc, nickel or the like. Such an aluminum alloy is lightweight, has high strength, and is a metal, so that it has a feeling of weight and heavyness peculiar to the metal, and is a preferable material for a rotor of a model rotorcraft (especially a radio control helicopter).

However, the specific gravity is large compared with, for example, carbon fiber, glass fiber, or wood (balsa material), and the weight is also a problem. That is, even when simply using aluminum alloy as a material of the rotor blades of the model rotorcraft, becomes in terms of weight or flying the model rotor blades aircraft becomes difficult or impossible.

In this respect, since the rotor blade according to the first invention of the present application is formed by molding an aluminum alloy tube, that is, a cylindrical material made of an aluminum alloy, it has a hollow structure (having a cavity inside). In particular, an integral hollow structure is formed . That is, since the inside of the rotor blade is hollow and configured so that metal (aluminum alloy) does not exist in that portion, the weight of the entire rotor blade can be significantly reduced. Therefore, the above weight problem can be solved.

Further, since the rotor blade according to the first invention of the present application is formed on the basis of an aluminum alloy tube, it has a seamless single layer structure (integrated structure) and sufficient strength.
Furthermore, the hollow structure and the single layer structure (integral structure) as described above are realized with a very simple structure in which an aluminum alloy tube that is originally hollow (cylindrical) is formed. For this reason, it is very advantageous also in terms of manufacturing man-hours and manufacturing costs. In other words, Ru der is possible to suppress the number of manufacturing steps and manufacturing cost. Also, for example, the length of the aluminum alloy tube, the wall thickness, cross-sectional dimensions and the like, depending on the size of the model rotorcraft for mounting the rotor blade, the length and determined as rotor blades of the model rotorcraft It may be matched with the size (area) of the blade cross section. In addition, since the standards and standards are determined for the blade cross-sectional shape, it is only necessary to conform to the standards and standards.

  As described above, the rotary wing according to the first invention of the present application is configured to be lightweight so that it can be used without any problem in a model rotary wing aircraft (for example, a radio-controlled helicopter), and can provide a heavy feeling and a heavy feeling. . For this reason, according to the first invention of the present application, in the model rotary wing aircraft, realism close to that of the actual aircraft can be obtained, and for example, it can meet the demands of lovers of radio controlled helicopters. Moreover, it can be manufactured at a lower cost.

Further, the rotary blade according to the second invention of the present application is an elongated cylindrical aluminum alloy tube having a desired dimension, the section viewed from one end in the longitudinal direction has a blade cross-sectional shape, and an integral hollow structure is formed inside. Thus , it is formed by press molding using a mold. For example, in a radio controlled helicopter, the rotor blade can be used as a main rotor blade (main rotor blade) or a tail rotor blade (tail rotor blade).

The rotor blade according to the second invention of the present application is press-molded from an aluminum alloy tube by a die, and has an integral hollow structure as in the first invention of the present application, and is greatly reduced in weight. According to the rotary wing according to the second invention of the present application, similar to the first invention of the present application, it can be used without any problem in a model rotary wing aircraft (for example, a radio-controlled helicopter), and a sense of weight and profoundness can be produced. Therefore, in the model rotary wing aircraft, realism close to that of the actual aircraft can be obtained.
Further, the rotor blades according to the first and second inventions of the present application can be formed of an aluminum alloy tube having a structure in which both ends in the longitudinal direction are closed. When forming such an aluminum alloy tube, it is considered that the internal pressure increases as the volume inside the aluminum alloy tube decreases, but this makes it possible to move from the inside of the aluminum alloy tube (the inside of the rotor blade) to the outside. Since pressure is applied toward the rotor blade, it is possible to provide resistance to unnecessary external pressure in the rotor blade. That is, even if a force that unnecessarily deforms the rotor blade is applied from the outside after the rotor blade is manufactured, it can be prevented from being easily deformed by the air pressure from the inside. Also, even if a part of the rotor blade is dented due to unnecessary external force, the air pressure from the inside acts as a restoring force, and the recessed part may return to its original normal shape. Conceivable.

Further, the present third invention is a manufacturing method of the rotor blades of the model rotorcraft, the aluminum alloy tube of the desired dimensions in elongated cylindrical, with cross section as viewed from the longitudinal one end having an airfoil cross-sectional shape In order to form an integral hollow structure inside, the rotor blade is formed by roll forming by applying pressure from two opposite directions to the aluminum alloy tube while feeding by the feeding device for feeding the aluminum alloy tube. It is characterized by.

According to such a manufacturing method, it is possible to manufacture a rotor blade according to the present Application onset bright as described above by easy single process. Therefore, it is possible to reduce the number of manufacturing steps and manufacturing costs.

In addition, the manufacturing method according to the fourth invention of the present application is an elongated cylindrical aluminum alloy tube having a desired dimension, a cross section viewed from one end in the longitudinal direction has a blade cross section, and an integral hollow structure is formed inside. as that is a production method characterized by by press molding makes with the rotary blade by a die.

According to such a manufacturing method, it is possible to manufacture a rotor blade according to the present Application onset bright as described above by easy single process. Therefore, it is possible to reduce the number of manufacturing steps and manufacturing costs.
In the manufacturing method according to the third and fourth inventions of the present application, the rotor blade can be formed using an aluminum alloy tube having a structure in which both ends in the longitudinal direction are closed as the aluminum alloy tube. According to this, it is possible to obtain the above-described effect that the rotor blade can be resistant to unnecessary external pressure.

It is an external view of the radio controlled helicopter 1 of this embodiment. It is drawing which represents the external appearance and side cross section of the main rotor blade 5a of this embodiment. It is drawing showing the manufacturing method (roll forming) of the main rotor blade 5a of this embodiment. It is drawing showing the weight characteristic of the main rotor blade 5a in this embodiment. It is drawing showing the manufacturing method (press work) of the main rotor blade 5a of this embodiment. It is drawing showing the other manufacturing method of the main rotor blade 5a.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is an external view showing an example of a radio control helicopter as a representative example of a model rotary wing aircraft to which the present invention is applied. In FIG. 1, the left side of the page is the front, the right side of the page is the back, the upper side of the page is the upper side, and the lower side of the page is the lower side.

A radio-controlled helicopter 1 shown in FIG. 1 is mainly composed of an airframe 2, a leg 3, a tail pipe 4, a main rotor 5, a tail rotor 6, and a tail 7.
Although not shown, an engine that generates driving force, a control device that performs various controls, and the like are mounted below the front portion of the body 2.

The leg 3 is provided below the airframe 2 and supports the airframe 2 at the time of grounding (at the time of landing).
The main rotor 5 includes an output shaft 8 that extends substantially vertically upward and rotates by driving the engine, and a pair of main rotor blades (hereinafter also referred to as main rotor blades) 5a and 5a. The main rotor blades 5a and 5a are attached to the output shaft 8, and rotate with the rotation of the output shaft 8 to generate lift.

  The tail rotor 6 is provided on the rear end side of the tail pipe 4 and includes a rotary shaft 9 extending in the front and back direction on the paper surface and a pair of tail rotor blades (hereinafter also referred to as tail rotor blades) 6a and 6a. Yes. The tail rotor blades 6a, 6a are attached so as to be rotatable about a rotation shaft 9. The tail rotor 6 rotates in synchronization with the rotation of the main rotor 5, and has a function of canceling torque (yawing) generated with the rotation of the main rotor 5 and stabilizing the behavior of the machine body 2.

The tail 7 is provided for improving maneuverability, for example.
FIG. 2 is a drawing showing an appearance and a side section of the main rotor blade 5a of the present invention. FIG. 2A shows the appearance of the main rotor blade 5a, and FIG. 2B shows a side cross section of the main rotor blade 5a. In addition, the side cross section of FIG.2 (b) is a X arrow directional view in Fig.2 (a). In other words, it is a cross-sectional view of the main rotor blade 5a as viewed from one end in the longitudinal direction. In FIG. 2A, A indicates the blade length, and B indicates the blade width.

As shown in FIG. 2B, the main rotor blade 5a has a blade cross-sectional shape. Since the blade cross-sectional shape is well known, detailed description thereof is omitted here.
In particular, the main rotor blade 5a in the present embodiment is made of an aluminum alloy, and is configured to have a cavity inside as shown in FIG. 2 (b). That is, it has a hollow structure.

Next, a method for manufacturing the main rotor blade 5a in this embodiment will be described with reference to FIG. In FIG. 3, the upper side of the page is the upper side, and the lower side of the page is the lower side.
The main rotor blade 5a of this embodiment is manufactured based on a cylindrical aluminum alloy tube 10.

  FIG. 3 shows a side cross-section of the aluminum alloy tube 10, and the aluminum alloy tube 10 has the same length as the blade length A (see FIG. 2) in the front and back direction of the paper surface. Further, the diameter and thickness of the aluminum alloy tube 10 are determined in accordance with, for example, the blade width B (see FIG. 2).

  And in the manufacturing method which concerns on this embodiment, the aluminum alloy pipe 10 as shown in FIG. 3 is shape | molded by roll forming so that a cross section may become a blade cross-sectional shape. More specifically, while feeding the aluminum alloy tube 10 by a feeding device (not shown), pressure is applied to the aluminum alloy tube 10 from above and below and the magnitude of the pressure is adjusted. As a result, the aluminum alloy tube 10 is crushed in the vertical direction and formed into an airfoil. Such forming may be completed by a single feeding operation for the aluminum alloy tube 10 or may be completed through a plurality of feeding operations. In the latter case, that is, the aluminum alloy tube 10 may be gradually formed into an airfoil by a plurality of forming steps.

FIG. 4 is a diagram showing the weight characteristics of the main rotor blade 5a according to this embodiment.
Here, five types of main rotor blades made from different materials were prepared as samples (1) to (5), and their weights were compared. Samples (1) and (2) are examples to which the present invention is applied (hereinafter also referred to as invention application examples 1 and 2, respectively), and samples (3) to (5) are comparative examples (hereinafter, respectively). Comparative examples 1, 2 and 3 are also described). The main rotor blades of Samples (1) to (5) were unified so that the blade length A was 570 mm and the blade width B was 50 mm. In addition, the blade cross-sectional shape was unified.

The main rotor blade of Invention Application Example 1 (Sample (1)) was prepared using an aluminum alloy tube 10 having a wall thickness t of 0.8 mm, and the weight was 130 g.
The main rotor blade of Invention Application Example 2 (Sample (2)) was prepared using an aluminum alloy tube 10 having a wall thickness t of 1.0 mm, and its weight was 160 g.

  The main rotor blade of Comparative Example 1 (Sample (3)) uses a solid aluminum alloy material. That is, it is the same as the invention application examples 1 and 2 in that an aluminum alloy is used, but it is configured not to have a hollow structure. In such a main rotor blade of Comparative Example 1, the weight was 400 g.

  The main rotor blade of Comparative Example 2 (sample (4)) is made of a carbon fiber that has been mainly used as a material for a rotor blade (main rotor blade) of a radio control helicopter. In such a main rotor blade of Comparative Example 2, the weight was 120 g.

  The main rotor blade of Comparative Example 3 (sample (5)) is made of wood (balsa material), which is the mainstream as the material of the rotor blade (main rotor blade) of the radio control helicopter. The main rotor blade of Comparative Example 3 is entirely covered with a film as a covering material. In such a main rotor blade of Comparative Example 3, the weight was 140 g.

  As can be seen from FIG. 4, if the main rotor blade 5a is constructed using a solid aluminum alloy material (refer to the sample (3)), it can be seen that there is a problem in terms of weight. That is, if an aluminum alloy is simply adopted as the material of the main rotor blade 5a, the weight becomes too large, and the flight of the radio control helicopter 1 becomes difficult or impossible.

  In this respect, in the present embodiment, the main rotor blade 5a is formed to have a hollow structure by molding the cylindrical aluminum alloy tube 10, and as shown in the invention application examples 1 and 2 in FIG. The overall weight can be greatly reduced. As a result, main rotor blades made of carbon fibers, for example, as shown in Comparative Example 2 (Sample (4)), and wood (balsa as shown in Comparative Example 3 (Sample (5)), which have been mainstream from the past. Compared with the main rotor blade made of a material, the weight is about the same. For this reason, it is sufficiently applicable as the main rotor blade 5a of the radio control helicopter 1, for example. Of course, the present invention can also be applied to the tail rotor blade 6a of the radio control helicopter 1. In addition, since the aluminum alloy tube 10 is manufactured by molding, it has a seamless single layer structure (integrated structure) and sufficient strength.

  According to the main rotor blade 5a of the present embodiment, realism (heavy feeling and profound feeling) peculiar to an aluminum alloy can be obtained, and in the radio control helicopter 1, realism close to that of a real helicopter can be obtained. Will be able to. For this reason, the radio control helicopter 1 can satisfy the demands of the enthusiast of the radio control helicopter who requires realism close to that of the actual machine.

Further, the main rotor blade 5a of the present embodiment has a very simple configuration in which an aluminum alloy tube 10 that is originally hollow (cylindrical) is formed. Therefore, the number of manufacturing steps and the manufacturing cost can be reduced. In addition, since it has a hollow structure, the amount of material used can be reduced, which can contribute to CO ₂ reduction, which has been a problem in recent years.
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 5, the second embodiment is the same as the first embodiment in that the main rotor blade 5a is manufactured by processing the aluminum alloy tube 10, but the main rotor blade 5a is formed by press working. It differs from the first embodiment using roll forming in that it is manufactured.

  That is, in the second embodiment, the aluminum alloy pipe 10 having a desired size is plastically processed by a mold to obtain the main rotor blade 5a. By manufacturing the main rotor blade 5a by plastic processing based on the aluminum alloy tube 10, the main rotor blade 5a having a hollow structure and a single layer structure (integrated structure) is manufactured as in the case of the first embodiment. Can do.

Compared with the roll forming of the first embodiment, the press working of the second embodiment can produce the main rotor blade 5a in a shorter time due to the press working characteristics. Become.
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, as shown in FIG. 6, an aluminum alloy plate 11 is formed to manufacture the main rotor blade 5a.
FIG. 6 shows a side cross-section of the aluminum alloy plate 11, and the aluminum alloy plate 11 has the same length as the blade length A (see FIG. 2) in the front and back direction of the drawing. The width dimension of the aluminum alloy plate 11 is determined in accordance with the blade width B (see FIG. 2) and the outer length of the blade cross section.

  Then, an aluminum alloy plate 11 as shown in FIG. 6 is formed into a blade cross-sectional shape by roll forming. And after shape | molding to a wing | blade cross-sectional shape, the long sides 11a of the aluminum alloy board 11 adhere | attach by press work.

  According to the third embodiment, the main rotor blade 5a having a hollow structure can be manufactured as in the first embodiment. Therefore, it is possible to provide the main rotor blade 5a that is lightweight so as to be applicable to the radio-controlled helicopter 1 and that has a realism (a feeling of weight and a feeling of heavyness) peculiar to an aluminum alloy (a characteristic of metal).

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various form can be taken within the technical scope of this invention.
For example, in the above-described embodiment, the case of the rotor blades (main rotor blade 5a and tail rotor blade 6a) of the radio control helicopter 1 has been described, but the present invention can be applied to all model rotor blade aircraft. For example, the present invention can be applied to a rotating blade in a gyroplane, an autogyro, a gyrodyne, or the like.

  Moreover, although the said embodiment demonstrated the example in which the main rotor blade 5a was manufactured based on the cylindrical aluminum alloy pipe 10, the aluminum alloy pipe 10 is not restricted to a cylindrical thing. For example, the main rotor blade 5a may be manufactured from an aluminum alloy tube having a square and cylindrical cross section. In some cases, the main rotor blade 5a may be manufactured from an aluminum alloy tube having a triangular and cylindrical cross section. In addition, for example, the cross section may be trapezoidal, or any material that can be usually obtained can be used.

  In the above embodiment, an example in which the main rotor blade 5a is manufactured has been described. However, the tail rotor blade 6a has a blade cross-sectional shape in the same manner, and can be applied to the manufacture of the tail rotor blade 6a. .

Moreover, you may make it heat-process in the main rotor blade 5a of the said embodiment. For example, the strength can be further improved by the heat treatment.
The main rotor blade 5a of the above embodiment may be plated. For example, corrosion resistance can be improved by plating. Moreover, a smoother and more glossy finished surface can be obtained, and added value can be added. Further, since the finished surface can be made smooth, it is possible to prevent the air flow around the blade during rotation from being disturbed, and the original function as the rotating blade can be enhanced.

  In addition, in the main rotor blade 5a of the above-described embodiment, it is needless to say that a process such as polishing the surface, coating, or coating the surface with a film may be added.

  In the first and second embodiments, it is also conceivable to use the aluminum alloy tube 10 in which both ends in the longitudinal direction are closed (the inside is sealed). In this case, a minute air hole is provided on the side surface of the aluminum alloy tube 10 so that the air inside the aluminum alloy tube 10 escapes to the outside during processing, and the aluminum alloy tube 10 is connected to the main rotor blade 5a. You may make it process into a shape. In this way, it is possible to prevent the internal air pressure from rising excessively, to facilitate processing, and to prevent the main rotor blade 5a from being deformed by excessive air pressure from the inside. it can. However, there can be a merit when the internal air pressure increases. This point will be described later.

  Further, there is a method of suppressing the increase in air pressure inside the aluminum alloy tube 10 only during the processing by processing the aluminum alloy tube 10 at a low temperature without providing an air hole on the side surface of the aluminum alloy tube 10. Conceivable. According to such a method, an excessive increase in the internal air pressure during processing is suppressed, and processing becomes easy. In addition, when it is set at room temperature after processing, it is considered that the internal air pressure increases as the temperature increases from low temperature to room temperature.

The following points can be considered as the merit of using the aluminum alloy tube 10 whose inside is hermetically sealed.
Specifically, when the aluminum alloy tube 10 is plastic processed into the shape of the main rotor blade 5a, the internal pressure may be increased due to a decrease in the internal volume. Since pressure is applied toward the outside, the main rotor blade 5a can be resistant to unnecessary external pressure. That is, even if a force that unnecessarily deforms the main rotor blade 5a is applied from the outside after the main rotor blade 5a is manufactured, the main rotor blade 5a can be prevented from being easily deformed by the air pressure from the inside. . Even if a part of the main rotor blade 5a is dented due to unnecessary external force, the air pressure from the inside acts as a restoring force, and the dented part returns to the original normal shape. It is also possible. Even in this case, the main rotor blade 5a may be subjected to heat treatment or plating treatment. Moreover, you may add processes, such as grind | polishing the surface, coating, or coat | covering the surface with a film.

  Further, in the above embodiment, after the main rotor blade 5a is manufactured, a process of increasing the air pressure of the hollow portion while closing the both ends in the longitudinal direction of the main rotor blade 5a to make the hollow portion a sealed structure. May be added.

DESCRIPTION OF SYMBOLS 1 ... Radio control helicopter, 2 ... Airframe, 3 ... Leg part, 4 ... Tail pipe, 5 ... Main rotor, 5a ... Main rotor blade, 6 ... Tail rotor, 6a ... Tail rotor blade, 7 ... Tail, 8 ... Output shaft, 9 ... Rotating shaft, 10 ... Aluminum alloy tube, 11 ... Aluminum alloy plate.

Claims (6)

A model rotorcraft rotor wing,
An aluminum alloy pipe having an elongated cylindrical shape and having a desired size is fed by a feeding device for feeding the aluminum alloy pipe and is subjected to roll forming by applying pressure from two opposite directions. but rotor blades, characterized in that one which is the roll forming as integral hollow structure is formed inside with cross section seen from one longitudinal end has a blade cross-sectional shape. A model rotorcraft rotor wing,
Aluminum alloy tube of the desired dimensions in an elongated cylindrical shape, so that the cross section as viewed from the longitudinal one end integral hollow structure therein and having an airfoil cross-sectional shape is formed, formed by press-molding by a die A rotating wing characterized by being a thing. The rotor blade according to claim 1 or 2,
A rotary blade characterized by being formed from the aluminum alloy tube having a structure in which both ends in the longitudinal direction are closed. A method for manufacturing a rotor of a model rotor wing,
An elongated cylindrical aluminum alloy tube having a desired dimension is sent out so that a cross section viewed from one end in the longitudinal direction has a blade cross section and an integral hollow structure is formed inside . A manufacturing method characterized in that the rotor blade is formed by roll forming which is fed by a feeding device and applies pressure from two opposite directions to the aluminum alloy tube . A method for manufacturing a rotor of a model rotor wing,
The aluminum alloy tube of the desired dimensions in elongated cylindrical, as in cross section seen from the longitudinal end integral hollow structure therein and having an airfoil cross-sectional shape is formed, the by press molding by a die A manufacturing method characterized by forming a rotary blade. It is a manufacturing method of Claim 4 or Claim 5,
The manufacturing method, wherein the rotary blade is formed using an aluminum alloy tube having a structure in which both ends in the longitudinal direction are closed as the aluminum alloy tube.

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