Rotor blade

Abstract

The present invention addresses the problem of providing a rotor blade that can be suitably applied as a rotor blade for UAM aircraft and has excellent impact resistance and maintainability. The gist of the present invention is a rotor blade that has at least a blade body part formed in an airfoil shape, and a member (leading edge protective member) that is detachably attached to the blade body part and forms a part of the leading edge of the rotor blade. The leading edge protective member is attachable to and detachable from the blade body part.

Description

rotor blades

[0001] The present invention relates to a rotor, and more particularly to a rotor with a leading edge protection member that can be suitably used for UAM (Urban Air Mobility) aircraft (so-called "flying cars").

[0002] Development of UAM aircraft is underway with the aim of easing traffic congestion in urban areas and securing transportation means to remote islands, etc., and one of the challenges in this process is how to design rotors for UAM aircraft.

[0003] Conventional rotorcraft for general aviation vehicles come in two types: a high-performance type with aircraft certification for Cessna aircraft, and a non-certified / low-cost type for drones. However, UAM aircraft are a relatively new field, and rotorcraft for UAM aircraft are considered unsuitable for either type due to cost and reliability considerations. However, since UAM aircraft fly over urban areas, if a rotor is damaged by a flying object such as a bird, making operation difficult, there is a risk of severe damage to the pilot and the ground. When actually designing, it is considered important to improve maintainability in addition to the impact resistance of the leading edge, which is most likely to be hit by a flying object.

[0004] Examining conventionally known rotor blades, for example, those disclosed in Patent Documents 1 and 2 can be cited. Patent Document 1 discloses a rotor blade for an unmanned aerial vehicle having a core containing a foamed material impregnated with a thermosetting resin inside a skin made of carbon fiber impregnated with a thermosetting resin. Patent Document 2 discloses a composite wing made of reinforced fiber and resin, in which a foaming agent is disposed between the suction side and ventral side of the wing, and the foaming agent is heated and expanded to form a suction side laminate, a ventral side laminate, and an internal foaming agent. Patent Document 3 discloses a structure in which a protective sheet made of a rubber layer is fixed with an adhesive to the leading edge of a wind turbine blade for impact resistance, tracking resistance, and ozone resistance. Patent Document 4 discloses a structure in which a metal such as nickel or titanium is adhesively bonded to the leading edge of a helicopter blade for wear resistance.

[0005] Patent No. 6971840 Patent No. 6789887 International Publication No. 2012 / 102294 JP 10-502594

[0006] The rotors for UAM aircraft disclosed in Patent Documents 1 and 2 do not disclose a structure for protecting the leading edge. Patent Documents 3 and 4 disclose structures for protecting the leading edge, but because they are for wind turbine or helicopter blades, they are fundamentally different in size, use, overall shape, and structure from rotors for UAM aircraft, making them difficult to apply to rotors for UAM aircraft. Furthermore, because the leading edge and protective layer are adhesively bonded, removal is time-consuming, posing maintenance challenges.

[0007] An object of the present invention is to provide a rotor that is particularly suitable for use in a rotor for a UAM aircraft and that has excellent impact resistance and maintainability.

[0008] To solve these problems, the present invention employs any of the following solutions: [1] A rotor having at least a blade body molded in the shape of a blade and a member (leading edge protection member) detachably attached to the blade body and forming part of the leading edge of the rotor. [2] The rotor described in [1] above, in which the blade body is composed of a skin, a plate-like member made of a fiber-reinforced composite material that forms the outer surface of the blade, and a shear web that supports the skin. [3] The rotor described in [1] or [2] above, in which the detachable mechanism is either or both of a screw mechanism and a fitting mechanism. [4] The rotor described in [3] above, in which the blade body side of the fitting mechanism is composed of a metal member attached to the blade body, and the metal member is embedded in the blade body to a depth of 5 mm or more. [5] The rotor described in [3] above, in which the blade body side of the fitting mechanism is composed of a fiber-reinforced resin member containing discontinuous fibers and a thermoplastic resin. [6] The rotor according to [4], wherein the metal member on the blade main body side of the fitting mechanism has a function of adjusting the center of gravity. [7] The rotor according to any one of [1] to [6], wherein the blade main body is offset by the thickness of the leading edge protection member at the location where the leading edge protection member is attached. [8] The rotor according to [7], wherein the offsetting position is within a range of 30% from the leading edge of the leading edge toward the trailing edge (where the distance from the leading edge of the leading edge to the rearmost edge of the trailing edge is taken as 100%) when viewed in any cross section perpendicular to the longitudinal direction of the rotor. [9] The rotor according to any one of [1] to [8], wherein the leading edge protection member is made of either or both of a fiber-reinforced composite material and a metal.

[10] The rotor according to any one of [1] to [8], wherein the leading edge protection member is configured to have a pre-penetration velocity V measured in accordance with ASTM D8101. ５０

[10] The rotor according to any one of [1] to [9], characterized in that the leading edge protection member is made of a material having a velocity of 120 m / s or more.

[11] The rotor according to any one of [1] to

[10] , characterized in that the leading edge protection member includes a portion made of a fiber-reinforced composite material and a portion made of a metal, and has a portion where the metal is exposed on the outer surface side and a portion where the fiber-reinforced composite material is exposed on the blade main body side.

[12] The rotor according to

[11] , characterized in that the area where the metal is exposed on the outer surface side of the leading edge protection member is smaller than the area of ​​the surface on the outer surface side of the leading edge protection member.

[13] The rotor according to any one of [1] to

[12] , characterized in that the leading edge protection member is attached at a position where the ratio (r / R) is 0.4 or more, where r is the distance from the blade root to the end of the leading edge protection member and R is the blade length.

[14] The rotor according to any one of [3] to

[13] , characterized in that, when the length of the leading edge protection member in the blade span direction is 100%, the length engaged by the engaging mechanism is 20% or more and 90% or less.

[0009] The rotor of the present invention can be suitably applied to rotors for UAM aircraft, and can provide rotors that are excellent in impact resistance and maintainability.

[0010] Fig. 2 is a schematic top view of a rotor according to an embodiment of the present invention. Fig. 3 is an example of a cross-sectional view taken along line A-A' in Fig. 1. Fig. 4 is another example of a cross-sectional view taken along line A-A' in Fig. 1. Fig. 5 is another example of a cross-sectional view taken along line A-A' in Fig. 1. Fig. 6 is an example of an arrangement of a leading edge protection member. Fig. 7 is a diagram illustrating the arrangement of a shear web. Fig. 8 is a diagram illustrating the arrangement of a shear web. Fig. 9 is a cross-sectional view illustrating an example of a leading edge protection member.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention should not be construed as being limited to these examples.

[0012] The rotor of the present invention has at least a blade body formed in the shape of a blade and a member (hereinafter referred to as a "leading edge protection member") that is detachably attached to the blade body and forms part of the leading edge of the rotor. That is, the leading edge protection member is detachably attached to the blade body and forms part of the leading edge of the rotor. The detachable mechanism is preferably either or both of a screw mechanism and a fitting mechanism.

[0013] The leading edge protection member may be a single member or multiple members. That is, multiple members can be attached to the leading edge of the wing to protect the leading edge. Furthermore, when attaching multiple members to the leading edge of the wing, each member can be independently equipped with a detachable mechanism. For example, when n members (n is an integer of 2 or greater) are used, n-1 members can be attached using a fitting mechanism, while the remaining member can be attached using a screw mechanism. This configuration allows for a strong attachment with little play.

[0014] The mating mechanism is composed of a male and female member that fit together. In the present invention, it is preferable that the blade body be the male member and the leading edge protection member be the female member. The female portion can be easily fabricated by providing a groove in the blade body or the leading edge protection member, or by embedding a metal member with a mating groove in the blade body or the leading edge protection member. The male portion can be provided during molding of the blade body or the leading edge protection member, but it is preferable to embed a mating male member in the blade body or the leading edge protection member (see mating member 5 in Figure 2). It is preferable that the mating portion between the male and female members be discontinuous in the longitudinal direction of the leading edge. Furthermore, when the length of the leading edge protection member in the blade span direction is taken as 100%, the total length of the mating portion is preferably 20% to 90%. The lower limit is more preferably 25% or more, and even more preferably 30% or more. If the gap is less than 20%, there is a concern that the leading edge protection member will not be firmly fixed to the wing body. On the other hand, the upper limit is more preferably 85% or less, and even more preferably 80% or less. If the gap exceeds 90%, it may be difficult to position the leading edge protection member along the shape of the wing body. Note that the portion of the groove (female mold) that is not involved in the fitting can be used as a guide groove.

[0015] When a fitting mechanism is employed, in the present invention, it is preferable that the blade body portion is a male member and that a metallic male member is embedded in the blade body. The metallic member is preferably embedded in the blade body to a depth of 5 mm or more, with the embedding depth t (see FIG. 2) being more preferably 6 mm or more, and even more preferably 7 mm or more. An embedding depth of 5 mm or more can further increase the stability of fixing the leading edge protection member against blade rotation. On the other hand, the upper limit of the embedding depth is preferably 20 mm or less, more preferably 18 mm or less, and even more preferably 15 mm or less. If it exceeds 20 mm, the weight of the rotor blade increases, which may result in a decrease in fuel efficiency.

[0016] On the other hand, from the viewpoint of impact resistance and moldability, it is preferable in the present invention that the blade main body is a male component, and that the male component is made of a fiber-reinforced composite material containing discontinuous fibers, i.e., discontinuous reinforcing fibers, and a thermoplastic resin, and is embedded in the blade main body. The reinforcing fibers and resin will be described later.

[0017] In the present invention, when a metal member is used in the screw mechanism or fitting mechanism, it can be used to adjust the natural frequency or center of gravity of the impeller. Because metal has a high specific gravity, it can be used to align the center of gravity of the impeller (note that this impeller means a rotor shaft with multiple impellers attached; the same applies throughout this paragraph) with the rotor shaft, or to adjust the natural frequency of the impeller to prevent resonance from occurring during rotation. Whether the metal member is used for this purpose can be determined by the change in natural frequency when the metal member is replaced with another material (e.g., a fiber-reinforced composite material) based on the alignment of the rotor shaft with the rotor shaft.

[0018] Figure 1 shows one embodiment of the rotor of the present invention used as a propeller blade. Figure 1 shows a top view of the rotor 1, with the tip 2a on the side farther from the center of rotation and the base 2b on the side closer to the center of rotation. Note that it is common for multiple blades to be provided from the center of rotation.

[0019] The present invention will be described with reference to the A-A' cross section of the rotor 1 (i.e., a cross section perpendicular to the longitudinal direction of the rotor 1) and examples shown in Figures 2 to 4. The example shown in Figure 2 comprises a wing body and a leading edge protection member 4, each of which is made up of an upper skin 3a forming the upper surface of the wing, a lower skin 3b forming the lower surface of the wing, and a foam core 6 supporting these. The wing body and the leading edge protection member are detachably fitted together by a fitting member 5. The fitting member 5 is fixed to the wing body, and its protruding portion fits into a groove provided in the leading edge protection member 4. The groove provided in the leading edge protection member extends along the wing edge, allowing the leading edge protection member to be attached to the leading edge by sliding it along the wing edge of the wing body. Furthermore, a portion of the groove in the leading protection member may be wider to accommodate the protruding portion of the fitting member. This eliminates the need to provide a groove over the entire portion corresponding to the wing edge. The fitting member may be continuous along the blade edge, but it is sufficient to have it on only part of the blade edge as long as it can secure the leading edge protection member. The fitting member 5 allows the leading edge protection member 4 to be easily fitted in and removed for maintenance. The interior of the rotor may be hollow, but may contain a core material such as a shear web 7 or foam core 6. From the perspective of achieving both lightweight and rigidity, a structure with a shear web 7 as shown in Figure 3 is preferable.

[0020] The screw fastening mechanism is comprised of a screw hole and a screw, the screw hole being provided in the leading edge protection member and the wing main body, and the screw threads into the screw hole provided in at least the wing main body. The screw hole preferably passes through the leading edge protection member, but can be filled in after the screw is threaded. The screw is preferably made of metal, and the screw hole can be provided by embedding a metal member having a threaded hole in it to increase the threading strength.

[0021] The example shown in Figure 4 has a wing body and leading edge protection member 4, which are made up of an upper skin 3a that forms the upper surface of the wing, a lower skin 3b that forms the lower surface of the wing, and a foam core 6 that supports them. The wing body and leading protection member are detachably fitted and screwed together using fitting members 5 and screws 9. Screwing with screws 9 securely fastens the leading edge protection member 4 to the wing body. When fastening with screws, holes for the screws 9 are provided in the leading edge protection member 4, and preferably enough space is provided to embed the screw heads. Holes for the screws 9 are also provided in the wing body. The locations and number of screws can be determined as long as the fastening is secure.

[0022] The leading edge protection member used in the present invention is preferably a fiber-reinforced composite material composed of reinforcing fibers and resin, a metal, or a combination thereof. From the viewpoints of durability and processability, aluminum, aluminum alloy, iron, magnesium, magnesium alloy, titanium, titanium alloy, zinc, or a zinc alloy is preferred. Among these, a preferred metal is one that includes a fiber-reinforced composite material portion and a metal portion, as illustrated in FIG. 9 , with the metal portion exposed on the outer surface and the fiber-reinforced composite material portion exposed on the blade body. Furthermore, more preferably, when the total area of ​​the outer surface is S (the area within the range indicated by a in FIG. 9 ) and the area of ​​the exposed metal portion is Sm, the relationship S > Sm is satisfied. In other words, the area of ​​exposed metal on the outer surface of the leading edge protection member is smaller than the area of ​​the surface adjacent to the outer surface. Adjusting the area of ​​exposed metal on the outer surface of the leading edge protection member facilitates adjustment of the natural frequency and center of gravity of the rotor blade of the present invention. However, in this case, it is desirable that metal be present in the portion corresponding to the forefront edge of the leading edge protection member. The upper limit of the ratio of Sm to S is preferably 0.90 or less, more preferably 0.85 or less, and even more preferably 0.80 or less. If it exceeds 0.9, the range in which the metal weight can be adjusted is small, and it may be difficult to achieve the desired natural frequency and center of gravity position of the rotor blade. On the other hand, the lower limit of the ratio of Sm to S is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. If it is less than 0.30, the exposed area of ​​the metal is small, and it may be difficult to achieve the desired effect of the metal.

[0023] As shown in Figure 9, by making the size of the leading edge protection member the same as the area where the leading edge protection member is attached on the blade body, the outer surface of the blade body and the outer surface of the leading edge protection member can be made into a continuous flat surface, which reduces the effort required for repair work to smooth the surface.

[0024] The leading edge protection member used in the present invention has a pre-penetration velocity V measured in accordance with ASTM D8101.５０ Preferably, the material has a velocity of 120 m / sec or more, more preferably 150 m / sec or more, and even more preferably 180 m / sec or more. There is no particular upper limit, but a velocity of about 300 m / sec is sufficient to provide protection. The material thickness during measurement is 2.5 mm ± 0.1 mm, and in the case of a laminated fiber-reinforced composite material, the lamination structure has the same orientation angle of the reinforcing fibers as the protective member. The velocity before penetration V ５０ If the wind speed is less than 120 m / sec, the impact resistance is poor, and the impact resistance performance of the leading edge protection member is not exhibited in the event of a bird strike, which may result in damage to the rotor blades.

[0025] Furthermore, when the leading edge protection member used in the present invention is made of a fiber-reinforced composite material, the difference in orientation of the reinforcing fibers of adjacent fiber-reinforced composite materials in the thickness direction is preferably within 45°, more preferably within 40°, and even more preferably within 30°. If the difference in orientation of the reinforcing fibers exceeds 45°, the desired impact resistance cannot be obtained, and there is a risk of breakage due to a bird strike. The reinforcing fibers and resins that are components of the fiber-reinforced composite material will be described later.

[0026] Furthermore, in the rotor of the present invention, when the distance from the blade root to the end of the leading edge protection member is r and the blade length of the rotor (the length from the center of rotation to the blade tip) is R, the mounting position of the leading edge protection member constituting the rotor of the present invention is preferably in a range where the ratio (r / R) is 0.4 or greater, more preferably 0.5 or greater, and even more preferably 0.6 or greater (see FIG. 5 ; the center of rotation is not shown). It goes without saying that r and R are in the same unit (e.g., centimeters). The upper limit is preferably 0.8 or less. If the ratio is less than 0.4, the weight and size of the leading edge protection member will increase, but the rotational speed and kinetic energy of the blade when a certain rotational force is applied will be small, which may result in insufficient effectiveness of the protective layer.

[0027] The blade length of the rotor of the present invention is preferably 2 m or less, more preferably 1.7 m or less, and even more preferably 1.5 m or less. If it exceeds 2 m, productivity may be poor and costs may increase. On the other hand, the lower limit of the blade length is preferably 0.5 m or more, more preferably 0.6 m or more, and even more preferably 0.7 m or more. If it is less than 0.5 m, it may lead to costs increasing in obtaining the required lift.

[0028] The rotor blade of the present invention preferably has a blade body made of a fiber-reinforced composite material, and is preferably composed of skins, which are plate-like members made of fiber-reinforced composite material that form the outer surface of the blade, and a shear web that supports the skins. The skins preferably consist of an upper skin that forms the upper surface of the blade and a lower skin that forms the lower surface of the blade, and the skins and shear webs are preferably made of fiber-reinforced composite material reinforced with continuous reinforcing fibers. The reinforcing fibers and resins that are components of fiber-reinforced composite materials will be described later.

[0029] To achieve the aerodynamic performance of the rotor blade of the present invention, it is important that the boundary between the outer surface of the leading edge protection element and the outer surface of the blade body is smooth. Therefore, the blade body is preferably offset by the thickness of the leading edge protection element at the location where the leading edge protection element is attached (i.e., the outer surface of the blade body is set back toward the center of gravity of the blade by the thickness of the leading edge protection element at the location where the leading edge protection element is attached; see symbol d in Figure 2). The offsetting position is preferably within a 30% range from the leading edge of the leading edge toward the trailing edge when viewed in any cross section perpendicular to the longitudinal direction of the rotor blade (where the distance from the leading edge of leading edge 6 to the rearmost edge of trailing edge 7 is taken as 100%).

[0030] The rotor of the present invention preferably has a hollow portion in the space between the upper and lower skins. The hollow portion (see reference numerals 8a and 8b in FIG. 3 ) formed therein reduces the overall rotor weight compared to a rotor containing a foaming agent or foam. This reduces the rotational drive power (e.g., the drive motor size), thereby promoting energy conservation and reducing the manufacturing cost of the aircraft. Furthermore, because the rotor is constructed of a composite material made of resin and reinforcing fibers, sufficient strength and rigidity can be ensured even when the blade thickness (wall thickness) is kept small. This is particularly true when carbon fiber is used as the reinforcing fiber. The volume of the hollow portion is preferably 50% or more of the total volume of the rotor. However, in order to ensure sufficient mechanical properties, the volume of the hollow portion is preferably 80% or less of the total volume of the rotor. Furthermore, there are no particular limitations on the thickness of the upper and / or lower skin as long as the necessary strength and rigidity are obtained, but from the viewpoint of weight reduction, the upper limit is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. If it exceeds 10 mm, it may lead to an increase in weight and cost. On the other hand, the lower limit of the thickness of the upper and / or lower skin is preferably 0.5 mm or more, more preferably 0.7 mm or more, and even more preferably 1 mm or more. If it is less than 0.5 mm, there is a possibility that resistance to impact may be insufficient.

[0031] When the blade length (length from the center of rotation to the blade tip) of the rotor of the present invention is R, the hollow ratio in the range from a position corresponding to 20% of the blade length from the blade root to a position corresponding to 80% of the blade length is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. If it is less than 50%, there is a concern that the weight reduction effect achieved by the hollow structure will be reduced.

[0032] When the blade body is composed of a skin and a shear web, the shear web preferably has a plate-like shape. In the case of a plate-like shape, there are no particular limitations on its shape in top view. It may be linear or curved, but it is preferable for it to have a bent portion. The top view refers to the direction from the upper skin to the lower skin, as shown in Figures 6, 7, and 8. Figures 7 and 8 show examples of shear web arrangements different from those shown in Figure 6. The shear web 7 in Figure 7 has a zigzag shape with bent portions, while the shear web 7 in Figure 8 has a wave-like shape with curved bent portions. The shape of the shear web in top view can be designed to any shape depending on the required rigidity and strength of the rotor blade.

[0033] In the rotor of the present invention, the maximum internal dimension of the hollow portion in the thickness direction of the orthogonal cross section at any point in the range from the blade root to a position corresponding to 80% of the blade length is preferably 2 mm or more. Rotors for UAM aircraft often have a blade length L of 1 m or less, and a maximum of 2 m is considered sufficient. Therefore, the desired weight reduction can be achieved by setting the maximum internal dimension of the hollow portion in the thickness direction of the orthogonal cross section at any point in the range from the blade root to a position corresponding to 80% of the blade length within that blade length to 2 mm or more. It is preferable that there are many portions in the orthogonal cross section where the maximum internal dimension of the hollow portion in the thickness direction of the blade is 2 mm or more, and it is preferable that this is satisfied in orthogonal cross sections at 50% or more of the length in the blade length direction, where the length is 100%.

[0034] It is also preferable that the hollow portion be provided with one or more shear webs extending in the blade span direction. In this case, two or more regions separated by the shear webs can be seen in a cross section perpendicular to the blade span direction. The example shown in Figure 3 has a shear web 7 extending in the blade span direction. Two regions 8a, 8b can be seen in the cross section. The provision of such a shear web 7 makes it possible to increase the overall strength and rigidity of the rotor blade. The number of shear webs extending in the blade span direction can be determined depending on the required rigidity and strength of the rotor blade, but one is preferred from the standpoints of formability and cost.

[0035] Furthermore, when viewed as a rectangle with the smallest circumscribing area in a projection obtained by irradiating a parallel beam perpendicular to the rotation plane of the rotor, the shear web preferably extends over 70% or more of the long side in the long side direction (spanwise direction) from the viewpoint of enhancing the rotor rigidity. Furthermore, in the short side direction (spanwise direction), the shear web preferably extends over 30% or more of the short side of the rectangle with the smallest circumscribing area in the projection. In this case, when there are multiple shear webs, the proportion of the shear web in the long side direction is determined based on a perspective view of all the shear webs.

[0036] The materials used for the rotor blade of the present invention and the method for producing the rotor blade will be described below with examples.

[0037] <Reinforcing Fibers> The fibers used in the fiber-reinforced composite material constituting the rotor blade of the present invention are not limited as long as they have a reinforcing effect, but it is preferable to use carbon fibers, glass fibers, aramid fibers, and metal fibers. Of these, it is preferable to use carbon fibers. The carbon fibers are not particularly limited, but for example, polyacrylonitrile (PAN)-based, pitch-based, and rayon-based carbon fibers are preferably used from the viewpoint of improving mechanical properties and reducing weight, and these may be used alone or in combination of two or more types. Of these, PAN-based carbon fibers are more preferable from the viewpoint of the balance between strength and elastic modulus of the resulting rotor blade.

[0038] The single fiber diameter of the reinforcing fiber is preferably 0.5 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more. The single fiber diameter of the reinforcing fiber is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The strand strength of the reinforcing fiber is preferably 3.0 GPa or more, more preferably 4.0 GPa or more, and even more preferably 4.5 GPa or more. The strand modulus of elasticity of the reinforcing fiber is preferably 200 GPa or more, more preferably 220 GPa or more, and even more preferably 240 GPa or more. If the strand strength or modulus of elasticity of the reinforcing fiber is within this range, the mechanical properties of the rotor can be improved.

[0039] The reinforcing fibers may be continuous (long fibers) or discontinuous (short fibers), and may be in the form of a woven or knitted fabric, such as an orthogonal biaxial woven fabric, a multiaxial woven fabric such as a non-crimp fabric or a braided substrate, or a multiaxial knitted structure.

[0040] <Matrix Resin> The resin used in the fiber-reinforced composite material constituting the rotor blade of the present invention serves as a matrix material encapsulating the reinforcing fibers. The matrix resin is not particularly limited, and thermoplastic or thermosetting resins can be used. Examples include thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, and cyanate resin; thermoplastic resins such as polyamide, polyacetal, polyacrylate, polysulfone, ABS, polyester, acrylic, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene, polypropylene, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer, PVC, and fluorine-based resins such as polytetrafluoroethylene; and silicone. Copolymers or modified products of these polymers can also be used. Multiple types of resins can also be used.

[0041] <Method for Manufacturing Rotor> The manufacturing process for the rotor of the present invention will be described using an example in which the skin is supported by a foam core. This manufacturing process includes (1) a skin molding process, (2) a foam core molding process, (3) a leading edge protection member molding process, (4) a skin and foam core joining process, and (5) a leading edge protection member attachment process to the blade body. Note that these processes can be performed in a single process (e.g., the skin molding and the skin and foam core joining are performed simultaneously), but for convenience they will be described separately. Each process will be described below using a specific example.

[0042] (1) Skin Molding Process Molding using a sheet-like fiber-reinforced composite material is simple. In particular, thermosetting prepreg or thermoplastic prepreg, known as an intermediate substrate in which reinforcing fibers are pre-impregnated with resin, can be preferably used as the sheet-like fiber-reinforced composite material. It is also possible to use a resin-free woven fabric, braiding substrate, NCF (non-crimp fabric), or the like, and impregnate the material with resin during the molding process. Examples of molding methods that can be used include autoclave molding, press molding, transfer molding, AFP (auto fiber placement), and stamping molding.

[0043] During molding, a mold imitating the upper surface of the wing and a mold imitating the lower surface of the wing are used to obtain an upper skin imitating the upper surface of the wing and a lower skin imitating the lower surface of the wing.

[0044] Here, the prepreg is composed of reinforcing fibers and a matrix resin. The volume content of the reinforcing fibers contained in the prepreg is preferably 40% or more as a lower limit, more preferably 45% or more, and even more preferably 50% or more. If it is below 40%, there is a possibility that the desired mechanical properties will not be obtained when the molded product is formed. Furthermore, the upper limit of the volume content is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. If it exceeds 80%, voids may be included, which may impair the mechanical properties.

[0045] The lower limit of the weight of the reinforcing fibers contained in the prepreg is 50 g / m ２ More than 100 g / m ２ More preferably, 150 g / m or more ２ More preferably, it is 50 g / m or more. ２ If the weight is less than 1000 g / m, voids where no reinforcing fibers are present may occur within the surface of the prepreg, which may become the starting point of destruction. ２ Preferably, 600 g / m or less ２ More preferably, 400 g / m or less ２ More preferably, it is 1000 g / m ２If the thickness exceeds this value, heat may not be transferred uniformly to the inside during molding, and the desired quality may not be obtained. The basis weight of the reinforcing fiber is measured by cutting out a 10 cm square area from the reinforcing fiber sheet, measuring its mass, and dividing it by the area. The measurement is performed 10 times on different parts of the reinforcing fiber sheet, and the average value is the basis weight of the reinforcing fiber.

[0046] When attaching the leading edge protection member by fitting, the protruding portion is molded as part of the skin, or a separate protruding portion is prepared and fixed to the wing body. When attaching by screw, mounting holes are provided in the wing body.

[0047] (2) Foam Core Molding Process Although a wood core, for example, can be used as the foam core, in order to make the FRP molded product lightweight, a core material made of a resin foam is desirable. The foam material is not particularly limited, and polyimide, polyurethane, polystyrene, polyolefin, acrylic, etc. can be used. However, a foam with an apparent density of 0.025 g / cm is preferred because it is easy to handle, has good physical properties, and is cost-effective, and has strength that is not crushed by the pressure of the matrix resin. 3 The rigid polyurethane foams described above are most preferably used.

[0048] The shape of the core material can be obtained by cutting or carving it out from a block, or by injecting a mixed and stirred foaming material concentrate into an injection foaming mold made to the desired shape and allowing it to foam inside the mold. When using core materials with complex shapes, the latter method allows for efficient production.

[0049] (3) Molding Process of Leading Edge Protective Member Because the leading edge protective member has a complex shape, from the viewpoint of moldability, it is preferable to manufacture it using a discontinuous fiber-reinforced material such as a sheet-like prepreg in which reinforcing fibers are contained in a thermosetting resin and incised (such prepreg is called an "incised prepreg"), or long fiber pellets or short fiber pellets in which reinforcing fibers are contained in a thermoplastic resin. The fiber length of the discontinuous fiber is preferably 50 mm or less, more preferably 20 mm or less, and even more preferably 5 mm or less. If it exceeds 50 mm, resin-rich portions with a low probability of fiber presence may occur, which may result in molding defects. On the other hand, the lower limit of the fiber length of the discontinuous fiber is preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more. If it is less than 0.1 mm, the reinforcing effect of the discontinuous fiber is small and it may become a starting point for fracture.

[0050] The incised prepreg preferably has incisions regularly distributed throughout its surface, and the reinforcing fibers contained in the prepreg are cut at the locations of the incisions. Such regularly distributed incisions can be formed, for example, by the method described in Japanese Patent No. 5272418.

[0051] Incised prepreg tends to open and shift at the incisions, improving the extensibility of the prepreg in the reinforcing fiber direction. Furthermore, the incision insertion points open during flow during compression molding, separating the reinforcing fiber bundles, increasing flexibility and fluidity of the prepreg. From the viewpoint of fluidity, it is preferable to make the incisions throughout the entire thickness of the prepreg.

[0052] When single fiber pellets or long fiber pellets are used, they can be molded using a molding method such as injection molding.

[0053] (4) Step of joining the skin and foam core: The skin layer formed in step (1) is joined to the foam core formed in step (2). The joining method is not particularly limited, but welding or adhesion can be applied. A foamable adhesive is particularly preferred, as the adhesive will foam and harden due to the heat during molding, allowing for a gap-free joining.

[0054] (5) Step of Attaching the Leading Edge Protective Member to the Wing Body: The leading edge protective member formed in step (3) is attached to the wing body (the joint of the skin and foam core) formed in step (4). The attachment method can be selected from a detachable method using screws or a mating mechanism. When using screws, holes for the screws are provided in the leading edge protective member, leaving sufficient space for the screw heads to fit. Also, holes for the screws are provided in the wing body. Preferably, the screws are attached at three locations: the base end, the tip end, and an intermediate location between them. When using mating attachment, a mating member is fixed to the wing body, and the protrusion of the mating member is mated with a groove provided in the leading edge protective member. The groove provided in the leading edge protective member may have a wider portion to accommodate the protrusion of the mating member. The groove extends along the wing edge, and the leading edge protective member is attached by sliding it along the wing body. After attachment, the leading edge protection member is preferably fastened with screws at two locations, one on the base side and one on the tip side, in order to fix it in place.

[0055] In the embodiment in which the skins are supported by shear webs, the shear webs are prepared in the same manner as the skins, and in step (4) above, the shear webs are joined to the inner surface of the skins.

[0056] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment in any way, and any modifications are possible within the scope of satisfying the requirements defined in the present invention.

[0057] A rotor having a leading edge protection member according to the present invention is particularly suitable as a rotor for a UAM aircraft.

[0058] REFERENCE SIGNS LIST 1 Rotor 2a Tip of rotor 2b Root of rotor 3a Upper skin 3b Lower skin 4 Leading edge protection member 5 Fitting member 6 Foam core 7 Shear web 8a, 8b Hollow portion 9 Screw 10 Portion made of metal 11 Portion made of fiber reinforced composite material t Embedded depth d Offset length

Claims

1. A rotor having at least a blade body portion molded into the shape of a blade, and a member that is removably attached to the blade body portion and forms part of the leading edge of the rotor blade (hereinafter such a member will be referred to as the "leading edge protection member").

2. A rotor as described in claim 1, wherein the blade body is composed of a skin, which is a plate-like member made of fiber-reinforced composite material that forms the outer surface of the blade, and a shear web that supports the skin.

3. A rotor as claimed in claim 1 or 2, wherein the mechanism for enabling attachment and detachment is either or both of a screw fastening mechanism and a fitting mechanism.

4. The impeller as set forth in claim 3, characterized in that the blade body side of the fitting mechanism is composed of a metal member attached to the blade body, and the metal member is embedded in the blade body to a depth of 5 mm or more.

5. A rotor as set forth in claim 3, wherein the blade body side of the fitting mechanism is constructed from a fiber-reinforced resin member containing discontinuous fibers and thermoplastic resin.

6. The rotor according to claim 4, wherein the metallic member of the fitting mechanism on the blade body side has a function of adjusting the center of gravity.

7. The rotor blade according to claim 3, wherein the blade body is offset at the location where the leading edge protection member is attached by the thickness of the leading edge protection member to be attached.

8. A rotor as claimed in claim 7, characterized in that the position where the offset processing is performed is within a range of 30% from the foremost edge of the leading edge towards the trailing edge when viewed in any cross section perpendicular to the longitudinal direction of the rotor (however, the distance from the foremost edge of the leading edge to the rearmost edge of the trailing edge is taken as 100%).

9. A rotor blade as claimed in claim 1 or 2, characterized in that the leading edge protection member is made of either or both of a fibre reinforced composite material and a metal.

10. The leading edge protection member has a pre-penetration velocity V measured in accordance with ASTM D8101. ５０ 3. The rotor according to claim 1, made of a material having a wind speed of 120 m / s or more.

11. A rotor as described in claim 9, characterized in that the leading edge protection member includes a portion made of fiber-reinforced composite material and a portion made of metal, has a portion where the metal is exposed on the outer surface side, and has a portion where the fiber-reinforced composite material is exposed on the blade body side.

12. A rotor as claimed in claim 11, characterized in that the area of ​​exposed metal on the outer surface side of the leading edge protection member is smaller than the area of ​​the surface on the outer surface side of the leading edge protection member.

13. A rotor as claimed in claim 1 or 2, characterized in that, when the distance from the blade root to the end of the leading edge protection member is r and the blade length of the rotor is R, the leading edge protection member is attached at a position where the ratio (r / R) is 0.4 or more.

14. A rotor as described in claim 3, wherein, when the length of the leading edge protection member in the blade span direction is 100%, the length engaged by the engaging mechanism is 20% or more and 90% or less.

Images