JPH0656093A - Rotor blade and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To reduce structural weight of a blade because of decreasing a bending load applied to the blade during flight by providing a warp upward in a condition with no external force acting so as to eliminate necessity for limiting a wind speed at the time of starting and stopping. CONSTITUTION:A rotor blade 4 is given a warp upward as in a broken line 4a in a condition with no external force acting. A shape of this warp is formed symmetrical to a shape where the blade of no warp is warped downward by force of 1G relating to a horizontal line. That is, the blade is manufactured in a manner wherein curvature is increased in accordance with approaching a mounting part relating to a rotary shaft 6 and decreased in accordance with approaching a free end. As a result, when not rotated, the rotor blade is almost horizontally placed by its own weight as in a full line 4b. Further when applied a load by a gusty wind or the like, the blade hangs down in a condition 4c of two-dot chain line, but a hanging down amount is decreased by an upward warp amount. Since a vertical tail 3 can be moved to a two-dot chain line 3b, a total length of a fuselage can be shortened by this amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor blade used for a rotor aircraft and a method for manufacturing the rotor blade.

[0002]

The main rotor of a rotorcraft has a large diameter, which is usually determined from aerodynamic characteristics. Therefore,
The rotor blade for a rotorcraft has a thin shape and a long shape with a large aspect ratio.

Further, in order to prevent the generation of an excessive bending moment due to a flight load, the root portion of the rotor blade is usually of a hinge structure which allows movement in the flap direction, the cord direction and the pitch direction. is there. When the rotary blade is rotating, the rotary blade is pulled in the direction of the resultant force of the centrifugal force and the lift generated by the blade, and can continue to rotate in a stable state. However, when the rotorcraft is on the ground and the rotor blades are not rotating, the thin and long blades cause vertical deflection even with a slight wind. As mentioned above, since the hinge is provided at the root of the blade, the blade can freely swing in the vertical direction about the root, so that the blade interferes with the body.
Therefore, the root of the blade is usually provided with a stopper for limiting the downward movement of the blade.

Therefore, when the rotor is on the ground, the rotor is stationary, and there is no wind, the broken line 1a in FIG.
As shown by, a downward load of 1.0 G acts on the blade 1 attached so as to extend in a straight line in a substantially horizontal direction orthogonal to the rotation axis 6 of the rotary blade due to its own weight.
In that case, the blade 1 is a cantilever beam with an evenly distributed load, and the distribution of displacement and bending moment along the beam is as shown in FIG. 6 according to the teaching of material mechanics. That is, since the bending moment changes in proportion to the square of the distance from the tip of the blade, the curvature of the blade is large at the root portion and gradually decreases as it approaches the tip. Further, the bending angle of the blade root portion linearly affects the displacement amount of the blade tip.

Therefore, the rotorcraft 2 is on the ground,
When the rotor is stationary, the blade 1 is shown by the solid line 1b in FIG.
As shown by, it is in a state of being bent downward. In this state,
When an external force in the vertical direction is applied by a gust of wind or the like, the blade 1 is further deflected in the vertical direction, and in some cases, when it is deflected downward, it is in a state of being in contact with the body 2 as indicated by a chain double-dashed line 1c in FIG. .

A particular problem in the operation of the rotary wing machine is the hanging of the blade. When starting or stopping the rotor blade under strong wind, the centrifugal force acting on the rotor blade is still insufficient to hold the rotor blade horizontally, and the blade is swirled by the wind and violently moves vertically (float). Wrapping). In general, rotorcraft are designed in consideration of the operation under strong winds, but there are still often accidents where the rotor blades come into contact with a part of the fuselage.

In order to prevent such an accident, the rotor blade and the fuselage may be designed to be sufficiently separated from each other. For that purpose, a mast for supporting the rotor blade (reference numeral 7 in FIG. 5). Need to be long. However, since the length of the mast affects the load and weight applied to the entire aircraft,
It is difficult to design with sufficient distance between the wings and the fuselage while the aircraft is on the ground.

The maximum wind speed that is considered to be encountered when actually operating a rotary wing aircraft is approximately 45 knots (23 m / s).
The downward acceleration that is considered to occur in the rotor blades at this wind speed is about 3.0 G. However, in consideration of the above points, in the conventional rotary wing machine, when a downward acceleration of approximately 2.3 to 2.6 G is applied to the blades, as shown in FIG.
It is designed so that the blade and the body interfere with each other as indicated by 1c. Therefore, in the conventional rotorcraft, starting the rotor blade,
There were many cases where a wind speed limit was set at the time of stop.

However, providing such a limitation is
It is not desirable in operation.

An example of a mechanism for solving the above-mentioned problem of the drooping of blades of a rotary wing aircraft is disclosed in Japanese Patent Laid-Open No. 61-247.
It is disclosed in Japanese Patent Publication No. 596. The mechanism tries to prevent the flapping of the blade by restraining the above-mentioned flapping hinge part when the rotational speed of the rotary blade is low. Although various other mechanisms have been proposed,
Generally, the structure is complicated, and since it includes the part that comes into contact with the blade when it starts and stops rotating, it often has difficulty in durability. There's a problem. Recently, a rotary blade root structure using a flexible girder made of a composite material instead of a hinge has been developed, but in such a structure, it is difficult to provide the above-mentioned flapping prevention mechanism.

On the other hand, during flight, centrifugal force and lift force due to rotation act on the rotor blades, but the resultant force acts on the inside of the blades to bend the blades upward. Therefore, it is necessary to increase the structural strength of the blade to withstand it, and there is a problem that the structural weight increases correspondingly.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional rotor blades of a rotorcraft, and is provided with a wind speed limitation at the start and stop of the rotor, and a flapping of a complicated structure. It is possible to operate safely with respect to the acceleration corresponding to the wind speed that is usually encountered without providing a prevention mechanism, and it is added to the blade by the combined force of the centrifugal force acting on the rotor blade during flight and the lift. An object of the present invention is to provide a rotor blade capable of reducing a bending load and a manufacturing method thereof.

[0013]

The rotary wing blade of the rotary wing aircraft of the present invention for solving the above-mentioned problems is characterized by having a warp upward in a state where no external force is applied.

As described above, the method of manufacturing a rotary blade having an upward warp includes a method of forming a blade by molding a composite material, and a method of forming a blade by giving a warp to the blade, and a blade. There is a method of changing the coefficient of thermal expansion of the upper structural material and the lower structural material.

[0015]

As described above, since the blades are manufactured so as to have an upward warp in a state where no external force is applied to the blades of the rotor blade, when the blades are attached to the rotor blade aircraft, the aircraft is on the ground, When the blade tries to bend downward due to its own weight or due to an external force such as a gust of wind, the gap between the blade and the body increases as much as the blade is bent upward.

Therefore, by adopting the rotor blade of the present invention to the conventional rotorcraft, it is possible to operate the acceleration corresponding to the wind velocity that is usually encountered without any limitation on the wind velocity. Become.

Further, by bending the rotor blades and giving them a warp upward, it is possible to reduce the bending load due to the combined force of the centrifugal force and the lift force acting on the rotor blades during flight. Only can reduce the structural weight of the vane.

When the blade is manufactured by molding the composite with a mold, the blade can be molded with the mold warped upward and the blade can be curved upward. .

When the molding die is not warped and the coefficients of thermal expansion of the members arranged on the upper surface side and the lower surface side of the blade are changed, the molding time and the room temperature are changed. A warp can be obtained at room temperature due to a temperature change.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a rotorcraft equipped with rotor blades according to the present invention. Rotor blade 4
Is warped upward as indicated by a broken line 4a in the figure in the state where no external force acts. As shown in detail in FIG. 2, the shape of this warp is symmetrical with respect to the shape in which the blade having no warp described above is deformed so as to warp downward by the force of 1 G and which is symmetrical with respect to the horizontal line. . That is, the rotating shaft 6
It is manufactured so that the closer it is to the mounting portion 5 with respect to it, the larger the curvature, and the closer it is to the free end, the smaller the curvature.

Since the effect on the deformation of the blade tip becomes larger toward the root side, it is possible to obtain a sufficient effect only by giving an upward warp only to a portion inside the center. As described above, when the horizontal blade imparts the same amount of upward warp as the amount that the horizontal blade hangs down by the force of 1 G, when the aircraft is on the ground and is stationary and the rotor blade is not rotating, the rotor blade blade Is its own weight, as shown by the solid line 4b in FIGS.
It becomes a substantially horizontal straight line orthogonal to the rotation axis 6.

When a load is further applied by a gust of wind,
1 hangs down to a state 4c indicated by a chain double-dashed line in FIG. 1. In this state, a drooping amount is given in advance as compared with the conventional drooping state 1c in a gust of the rotor blade described in FIG. It becomes smaller by the amount of upward warp, and can maintain a state of being separated from the airframe 2 during a gust of a wind speed that is normally encountered.

In a rotary wing aircraft of the type in which there is only one main rotor as shown in FIG. 1 and an auxiliary rotor 8 for canceling the torque of the main rotor is provided at the tail, the vertical tail 3 is rearward. It is usual to make the shape inclined. this is,
It was decided to make the total length of the aircraft as short as possible and to secure a clearance with the main rotor.

As described above, since the front edge of the vertical stabilizer 3 is largely inclined, when the free ends of the rotor blades 4 are less drooping, the vertical stabilizer 3, which was conventionally located at the position indicated by the solid line 3a, is rotated. 3b indicated by a two-dot chain line in FIG. 1 approaching the wing
Can be moved to the position. As a result, the overall length of the airframe 2 can be shortened, the weight of the entire aircraft can be reduced, and the propulsion power can be reduced. Note that the amount of upward warp of the blade does not necessarily have to be equal to the amount of sag by the force of 1G.

The rotor blade having an upward warp according to the present invention can be applied to a metal rotor blade regardless of the material of the blade, but a molding die which has recently been put into practical use is used. It can be more easily applied to composite vanes that are molded. Since a blade made of a composite material is manufactured by molding with a molding die, if a predetermined warp is given to the molding die and molding is performed with the molding die, a blade having the required warp can be obtained.

As a method of imparting a required warp to the forming die, a method of processing the forming die into a shape with a required warp at the time of cutting is first conceivable. If it becomes necessary to change the amount of warp, the mold must be rebuilt from scratch.
Therefore, it is possible to process the forming die at a low cost without giving a warp, and to easily adjust the amount of warp as needed, thereby producing a blade with warp as much as necessary. The possible methods are described below.

FIG. 3 shows an example of an apparatus for carrying out the manufacturing method of the present invention. The mold for molding the blade with the composite material is the lower mold 11 having the molding surface 16 of the blade.
And a thin upper mold 15 that elastically deforms along with the lower mold 11. The molding surface 16 of the lower mold 11 is processed into the shape of a blade when there is no warp. The lower die 11 is pin-supported to the frame 13 having sufficient rigidity by the ear metal parts 12 at both ends, and is supported at a plurality of places between the ends (three places on each side in the example of the figure), from the center to both sides. By screwing the screw parts on both sides of the turnbuckle, which are screwed in the opposite direction, into the screw holes formed in the upper surface of the frame 13 and the lower surface of the lower mold 11, the upper surface of the frame 13 and the lower surface of the lower mold 11 are screwed. The distance between each position and can be adjusted.

The upper mold 15 is processed to be as thin as possible, positioned on the lower mold, and then elastically deformed along with the lower mold by pressure applied when the composite material is cured.

When the mold is to be warped upward as required by using this apparatus, the distance between the lower surface of the lower mold 11 and the upper surface of the frame 13 becomes smaller at the central portion than at both ends, and the lower surface of the lower mold 11 is reduced. By adjusting the tightening amount of each turnbuckle 14 so that the shape of is a required warp shape with respect to the straight line contacting the lower surface of the lower mold 11 at the position corresponding to the base end of the blade, the lower mold has a required shape. Elastically deforms into a warped shape. Therefore, if the blade is molded in this state, the blade is manufactured with the required warp applied upward. When the amount of warp is to be changed, the amount of warp can be easily and arbitrarily changed by changing the tightening amount of each turnbuckle.

Next, using a mold having a predetermined blade-shaped molding surface with no warp, without giving a warp to the mold,
Another manufacturing method of the present invention for manufacturing a blade that is warped upward by a required amount will be described.

The mold for molding the blade is composed of a lower mold and an upper mold as described with reference to FIG. 3, but a turnbuckle for imparting a warp to the lower mold is not provided,
Molding is always performed without warping.

The blade manufacturing method of the present invention will be described with reference to FIG.

In this example, the upper surface side structural member 22 arranged on the upper surface 21 of the blade and the lower surface side structural member 23 arranged on the lower surface side.
The blade is warped upward by utilizing the difference in coefficient of thermal expansion between the blade and the blade. For example, the upper surface side structure 22 is made of a material (for example, a glass fiber composite material or a metal material) having a coefficient of thermal expansion slightly higher than the average coefficient of thermal expansion of the structural material of the entire blade,
On the contrary, the lower surface side structural member 23 is made of a material (for example, carbon fiber composite material) having a coefficient of thermal expansion slightly smaller than the average coefficient of thermal expansion. Needless to say, either one of the upper and lower structural members can be omitted if sufficient deformation can be obtained.

The blade made of the composite material, in which the coefficient of thermal expansion of the material of which the upper surface is the lower surface is adjusted in this way, is molded and hardened by applying heat and pressure in the molding die. The high-strength composite material used for the blade generally cures at a high temperature of 120 ° C. or higher, but at this high temperature, the resin of the material flows so as to match the mold and reacts to cure. After that, the blades shrink according to the coefficient of thermal expansion during the cooling stage, but the material with the higher coefficient of thermal expansion shrinks more and tries to shrink the whole, and conversely, the material with the lower coefficient of thermal expansion shrinks the entire material. Try to hold down. As a result, as in this example, the coefficient of thermal expansion of the upper structural member 22 is
If it is larger than that of the lower surface side structural member 23, the blade will warp upward. Therefore, by appropriately adjusting the thermal expansion coefficients of the upper and lower structural members, it is possible to give the blade a desired amount of upward warp.

[0036]

As described above, it is necessary to set the wind speed limit at the time of starting and stopping the rotor blade of the rotor aircraft by the rotor blade according to claim 1, and to provide a flapping prevention mechanism having a complicated structure. Since it will be eliminated, the safety and operation of the aircraft can be secured and the reliability of the structure can be improved.
Since the hanging down of the rotor blades from the horizontal position is reduced, the vertical tail can be brought closer to the center of rotation of the rotor blade, which contributes to downsizing and weight reduction of the airframe. Further, since the bending load applied to the blade during flight is reduced, the structural weight of the blade can be reduced, which also contributes to weight reduction of the blade.

According to the rotary blade structure method described in claims 2 and 3, the forming surface of the forming die can be cut without considering the warp, the forming die manufacturing cost is reduced, and simple adjustment is possible. It is possible to give the required warp to the blades.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an example of a rotary wing aircraft equipped with rotary wing blades according to the present invention and a hanging state of the blades.

FIG. 2 is an explanatory diagram showing in detail states of the blade when there is no load and when the blade is hanging down by its own weight.

FIG. 3 is a perspective view showing an example of a molding die for manufacturing the rotary blade of the present invention with a composite material.

FIG. 4 is an explanatory view illustrating another example of a molding method when the rotary blade of the present invention is manufactured from a composite material.

FIG. 5 is an explanatory diagram illustrating an example of a conventional rotary wing aircraft equipped with rotary wing blades and a hanging state of the blades.

FIG. 6 is an explanatory view showing in detail a drooping state and a bending moment distribution when the blade is unloaded and drooping due to its own weight.

[Explanation of symbols]

 2 Rotor vane body 3 Vertical tail 4 Rotor blade 4a Blade position without load 4b Blade position when 1G load is applied 4c Blade position when load is further applied by gust 5 Rotor blade Mounting part 6 Rotational shaft 11 Lower mold for molding 12 Ear metal part 13 Frame structure 14 Turnbuckle 15 Upper mold 16 Mold molding surface 22 Upper surface side structural material 23 Lower surface side structural material

Claims (3)

[Claims] 1. A rotary wing blade of a rotary wing aircraft, which has a warp upward in a state in which an external force is not applied. 2. The method for manufacturing a rotor blade according to claim 1, wherein the rotor blade is manufactured by molding a composite material with a molding die, and the molding die is provided with a warp to be imparted to the blade. A method for manufacturing a rotary blade, wherein the molding die is fixedly supported by a mold, and the molding die is molded in that state. 3. The method for manufacturing a rotor blade according to claim 1, wherein the rotor blade is manufactured by molding a composite material with a molding die, and a coefficient of thermal expansion of a member arranged on an upper surface side of the blade. Is higher than the coefficient of thermal expansion of the member arranged on the lower surface side, is cured and molded at a temperature higher than room temperature in a mold formed in a shape without warping, and is cooled to room temperature to form the upper surface side member. A method for manufacturing a rotor blade, wherein a required warp is given to the blade by a difference in coefficient of thermal expansion of a lower surface side member.