JP3968634B2 - Twin-ducted fan-type tail rotor of rotorcraft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tail rotor of a rotary wing aircraft, and more particularly to a twin ducted fan type tail rotor.
[0002]
[Prior art]
As shown in FIG. 16, the conventional large rotor blade 31 having a total weight of 7 tons or more includes a main rotor 32 and a tail rotor 33, and the tail rotor 33 has the same format as the main rotor 32. In most cases, a propeller type composed of a plurality of exposed blades 34a, 34b, 34c, 34d is employed.
[0003]
Since this propeller-type tail rotor 33 is mounted on a thin tail boom 35, there are many problems in aeroelasticity, and a thrust drop phenomenon called a vortex ring state also occurs during a crosswind, and accidents often occur. . In addition, many fractures due to structural fatigue have been reported. However, the large-sized rotary wing aircraft 31 has not adopted anything other than the above-described conventional propeller-type tail rotor wing 33, and the above-mentioned accident or destruction is a major problem that must be solved for the rotary wing aircraft. It was one.
[0004]
On the other hand, a small rotorcraft having a total weight of 5 tons or less often uses a tail rotor 36 of a type called a ducted fan shown in FIG. 17 in addition to the propeller tail rotor described above. The tail rotor 36 includes a rotor assembly 37 and a duct 38 that covers the periphery of the rotor assembly 37. The ducted fan-type tail rotor blade 36 has an outer periphery of the rotor blade assembly 37 covered with a duct 38 as compared with a normal propeller-type tail rotor blade 33, so that maintenance personnel and crew are mistaken on the ground. Since the accident which contacts the blade | wing 39 can be prevented, it is very safe. Even in the air, accidents coming into contact with electric wires and trees can be prevented, and it is safe. Further, in terms of performance, since the blowing speed is high and it is surrounded by the duct 38, there is an excellent advantage that it does not enter a vortex ring state during a crosswind. As a prior art related to the noise reduction of the ducted fan, there is a tail rotor of a rotary wing aircraft disclosed in Japanese Patent Publication No. 2662838 (registered date: June 20, 1997).
[0005]
By the way, the reason why the ducted fan type tail rotor 36 has not been adopted in a large rotor aircraft having a total weight of 7 tons or more is because of the following problems.
[0006]
(1) Because of the large diameter, the bottom rub angle is small and the ground clearance cannot be increased.
When the conventional ducted fan type rotor blade is designed for the tail, the diameter becomes larger than the size of the fuselage, and a line L connecting the wheel contact point T to the lower end of the rear end of the tail boom 35 as shown in FIG. The angle formed by the ground G at the time of normal landing, that is, the rubbing angle α becomes small, and the cause operation called flare for decreasing the speed at the time of landing becomes impossible. This is because the size of the cabin is almost determined by the height of the person's back, and it does not differ greatly between large and small machines, whereas the size of the tail rotor 36 is proportional to the total weight of the aircraft. Because it becomes.
Further, in the conventional propeller-type tail rotor blade 33 shown in FIG. 16, the tail boom 35 is bent upward in the middle to increase the attachment position of the tail rotor blade 33 and increase the distance from the ground G. The angle α can be increased and the ground clearance can be increased. However, the ducted fan type tail rotor blade 36 is often installed on the extension of the tail rotor blade rotation shaft 40 as shown in FIG. The angle α decreases and the ground clearance decreases.
(2) The vertical tail is thick and the resistance is large.
In the ducted fan type tail rotor blade 36, the thickness of the duct 38 on the outer periphery of the rotor blade assembly 37 needs to be about 40% of the rotor blade diameter. For this reason, when the diameter of the rotary blade increases, the thickness of the duct 38, that is, the thickness of the vertical tail 41 becomes very thick, and the air resistance increases and the performance deteriorates.
(3) The weight of the airframe structure increases.
Due to the large diameter, the vertical tail 41 becomes large and the structural weight increases. That is, the ducted fan type tail rotor blade requires a duct surrounding the outer periphery of the rotor blade, but if it is large, the weight of the duct portion increases and becomes heavy.
[0007]
[Problems to be solved by the invention]
Accordingly, the present invention aims to provide a rotorcraft having excellent performance and safety by improving a ducted fan type tail rotor so that it can be applied to a large rotorcraft having a total weight of 7 tons or more. It is.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, the twin ducted fan type tail rotor of the rotorcraft according to the present invention has two ducted fan rotors in the rear end of the tail boom and the vertical tail of the rotorcraft. Embedded in the top and bottom, a plurality of blades in the two ducted fan type rotor blades are attached to the hub at the center of rotation so that only the pitch angle can be changed,
In each ducted fan type rotor blade, the rotational driving force of the driving rotary shaft provided at the upper part of the tail boom is transmitted to the gear box of the lower rotor blade, and the rotational driving force from the gear box of the lower rotor blade is received. Is transmitted to the gear box of the upper rotor blade via the drive shaft,
Each gear box is provided at the center of rotation .
[0009]
In twin ducted fan-type tail rotor of the rotorcraft above, two ducted-fan rotor blade, rotational speed is preferably different.
[0010]
The two ducted fan type rotor blades preferably have different numbers of blades.
[0011]
Further, it is also preferable that the two ducted fan type rotor blades have different rotational speeds and different numbers of blades.
[0012]
In the twin ducted fan type tail rotor of each rotorcraft described above, it is also preferable that the control of the two ducted fan rotors is controlled by one actuator.
[0013]
It is also preferable that the control of the two ducted fan type rotor blades is independently controlled. In this case, it is more preferable that one of the two ducted fan type rotor blades does not generate thrust during forward flight and generates thrust only during hovering.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a tail rotor of a rotorcraft according to the present invention will be described with reference to the drawings. In FIG. 1, 1 is a rotorcraft and 2 is a main rotor. Two ducted fan rotors 6 and 6 ′ having the same structure are embedded in the rear end portion of the tail boom 4 and the vertical tail 5 extending to the rear of the fuselage 3 of the rotary wing aircraft 1. -Constructs a fan-type tail rotor blade. FIG. 2 is a perspective view of the twin ducted fan-type tail rotor blade as viewed from the left front. In this case, the wind is blown in the direction of the arrow. FIG. 3 is a perspective view of the tail rotor blade viewed from the right front. Reference numeral 7 in FIGS. 2 and 3 denotes a horizontal tail attached to the lower part of the rear end of the tail boom 4.
[0015]
The twin ducted fan type tail rotor blade having the above configuration has a high ground height H because the two ducted fan rotor blades 6 and 6 'have a small diameter. Therefore, it is easy to load the luggage from behind the cabin. Further, since the angle formed by the line L connecting the wheel ground contact point T to the lower end of the rear end of the tail boom 4 and the ground G at the time of normal landing, that is, the bottom rubbing angle α, is called flare for reducing the speed at the time of landing. Sufficient margin is created for the operation of the cause and the safety is increased. In addition, it takes less distance and time to land. Furthermore, since the rotor blades 6 and 6 'are covered with the duct, collision with trees, electric wires, etc. can be prevented, and safety is high.
Further, since the diameters of the rotor blades 6 and 6 'are small, the thickness of the duct may be reduced accordingly, and thus the thickness of the vertical tail 5 may be reduced. Therefore, the air resistance is low and the performance is improved. Furthermore, since the rotary blades 6 and 6 'are small, the blowing speed can be increased. For this reason, the vortex ring state is not entered, and safety is enhanced even in a flight in a strong crosswind state.
[0016]
The two rotor blades 6, 6 ′ of the twin ducted fan type tail rotor blade of the above embodiment are driven by the rotational driving force from the drive rotating shaft 8 attached to the upper part of the tail boom 4 as shown in FIG. 4. It can be rotated. That is, the rotational driving force of the drive rotary shaft 8 changes the rotational direction in the gear box 9 'of the lower rotary blade 6', first rotates the lower rotary blade 6 ', and then from the gear box 9'. The upper rotor blade 6 is rotated via a drive shaft 10 that extends obliquely upward and is connected to the gear box 9 of the upper rotor blade 6. As shown in FIGS. 5 and 6 , the blades 11 and 11 'of the two upper and lower rotor blades 6 and 6' rotated by the rotational driving force of the drive rotating shaft 8 are placed in the gear boxes 9 and 9 '. Only the pitch angle is attached to the hubs 12 and 12 'at the center of rotation. The change of the pitch angle of the blades 11 and 11 'is achieved by moving the link 13 shown in FIG. 5 constituting a part thereof through a control system (not shown) by the pilot operating the pedal. The thrust of the two rotor blades 6 and 6 'is varied. An actuator (not shown) for supplementing human power and converting a control signal from the computer into an operating amount of the link 13 is mounted between the pedal and the link 13.
[0017]
The thrusts of the two upper and lower rotor blades 6, 6 'need not always be the same. Therefore, it is also one of the preferred embodiments of the present invention that the control system after the actuator is branched by the upper rotor blade 6 and the lower rotor blade 6 'and is individually controlled independently. .
[0018]
The upper rotor blade 6 is embedded in the vertical tail blade 5, but the thickness of the vertical tail blade 5 is thin as shown in FIG. 6, and its performance is lower than that of the lower rotor blade 6 ′. This is because in a ducted fan type rotor blade, the thickness of the duct needs to be about 40% of the rotor blade diameter, and the performance decreases as the thickness becomes thinner. In addition, when thrust is generated during cruising (forward flight), the pressure distribution around the vertical tail changes, and a large torsional moment is generated in the vertical tail. During cruise (forward flight), the vertical tail itself can generate lift to cancel the torque generated by the main rotor. Therefore, it is preferable that the upper rotor blade 6 does not produce thrust during cruising (forward flight). On the other hand, since the lift of the vertical tail disappears during hovering, it is necessary to balance the torque of the main rotor only with the thrust of the tail rotor. Therefore, in this case, it is preferable to perform control so that the maximum thrust is also generated in the upper rotor blade 6. Thus, it is the most preferable embodiment of the present invention to individually control the thrusts of the upper and lower ducted fan type rotor blades 6 and 6 'so as to suit the operating conditions.
[0019]
FIG. 7 is a cross-sectional view taken along the line CC of FIG. 4, and the upper and lower ducted fan rotor blades 6 and 6 'are connected by the drive shaft 10, but the reduction ratio of the gear boxes 9 and 9' is shown. By making these different, the rotational speed (rotational speed) of the upper and lower rotary blades 6 and 6 'can be made different. By doing so, it is possible to expect an effect that the frequency pattern of the noise generated from the tail rotor changes so that it cannot be heard loudly by human ears. This can also be achieved by making the number of blades 11, 11 'of the upper and lower rotor blades 6, 6' different. Of course, if the rotational speeds of the upper and lower rotor blades 6 and 6 'are made different and the number of blades 11 and 11' are made different, the effect is further improved.
[0020]
The upper and lower ducted fan rotor blades 6 and 6 'have the same configuration. FIG. 8 shows the assembled state and FIG. 9 shows the disassembled state. Each of the blades 11 is attached to a double flange portion on a hub metal fitting 16 attached to an output shaft 22 extending from the gear box by two bearings 17 so as to be rotatable around the pitch shaft 18. The pitch angle of the blades 11 can be changed by moving the pitch horn 19. The pitch horn 19 is coupled to a stud 21 attached to a spider 20 of a control system, and the spider 20 is coupled to a distal end portion of a push rod 23 that is disposed coaxially with the output shaft 22. The push rod 23 is coupled to the link 13 shown in FIG. Because of this configuration, the control steering amount automatically controlled by the pilot and the computer is converted from the link 13 to the pitch angle change amount of the blades 11, and the thrust of the rotor blades is changed.
[0021]
The details of the gear box 9 ′ of the lower rotary blade 6 ′ will be described with reference to FIG. 10. The input rotational force from the main gear box is transmitted to the lower gear box 9 ′ via the drive rotary shaft 8. The transmitted rotational force is transmitted to the 'rotor blades 6 of the downwardly changing substantially its 1/2 90-degree direction by' the gear box 9, converts the direction and the remaining diagonally upward, the driving rotary shaft 8 ' Is transmitted to the upper rotor blade 6 via. In the figure, 25 is a temperature sensor. Normally, a gear box of a rotary wing aircraft transmits a large horsepower for its size, but is adjusted very precisely so as to reduce a transmission horsepower loss of gears and bearings. However, the transmission horsepower loss cannot be reduced to zero, and eventually all is converted into heat energy, so if the heat is not exhausted efficiently, it will be burned out quickly. In the conventional rotary wing aircraft shown in FIG. 16, a cooling device is attached to the intermediate gear box 42 of the tail rotor 33. However, in the case of the present invention, since the position of the intermediate gear box 42 is the lower rotor blade 6 ', sufficient cooling air is obtained by the wind generated by the rotor blade 6'. No special cooling device is required.
[0022]
11 is a cross-sectional view taken along the line DD in FIG. The rotational force transmitted from the drive rotary shaft 8 is transmitted from the spiral bevel gear 26 of the input pinion to the drive gear 27 of the lower rotary blade 6 'to rotate the rotary blade 6'. Furthermore spiral bevel gear 26 meshes with the drive gear 28 of the upper rotary blade 6, to rotate the rotor blade 6 a rotational force transmitted to the upper rotor blade 6. In the case of the intermediate gear box 42 of the tail rotor 33 of the conventional rotor aircraft shown in FIG. 16, the spiral gear bevel gear 26 of the input pinion directly meshes with the drive gear 28 of the rotor 6 above. In the present invention, the drive gear 27 of the lower rotor blade 6 'is merely added, and the increase in weight is slight. Moreover, since the cooling device is no longer necessary as described above, there are factors that reduce the weight, and the overall weight increase is slight. Further, since the upper rotor blade 6 consumes about 50% of horsepower, the upper gear box 9 becomes smaller. Therefore, the gearbox is totally lightweight.
[0023]
【The invention's effect】
As can be seen from the above description, according to the twin ducted fan type tail rotor of the rotorcraft of the present invention, the overall characteristics, performance, rotor system design, drive system design, airframe structure design, equipment design In terms of safety, manufacturing cost, operation cost, etc., the following effects can be obtained.
1) All-machine characteristics (1) The twin ducted fan type tail rotor blade has a small diameter and a large rubbing angle. Therefore, a sufficient margin is created for the operation for causing the landing, and the safety is improved. In addition, it takes less distance and time to land.
(2) Since the twin ducted fan type tail rotor blade has a small diameter and a high ground clearance, it is easy to load cargo from behind the cabin.
(3) Since the rotor blades are covered with ducts, collisions with trees, electric wires, etc. can be prevented, and safety is high.
(4) If one large-diameter rotor blade is divided into two, the total rotor blade area is designed to be the same, so the diameter of each rotor blade is 1 / √2. On the other hand, since the weight is proportional to the cube of the diameter, if there are two rotor blades having a diameter of 1 / √2, the total weight is 1 / √2, and the weight can be reduced.
2) Performance aspect (1) Since the diameter of the tail rotor blade is small, the duct thickness may be thin and the thickness of the vertical tail blade may be thin. Therefore, the air resistance is low and the performance is improved.
(2) Since it is a small rotor blade, the blowing speed can be increased. Therefore, the vortex ring state is not entered, and the stability is high even in a strong crosswind state.
(3) Noise can be reduced by combining two ducted fan tail rotor blades. For example, the noise can be heard as a chord by slightly changing the rotational speeds of the two tail rotor blades. Such tuning sounds to the human ear as if it is noisy. Such an effect is further improved by changing the number of blades of the tail rotor blades up and down or changing the mounting angle. Of course, if the number of rotations of the two tail rotor blades is changed and the number of blades is changed, the effect is further improved.
(4) As for the effect on performance by using two ducted fan-type tail rotor blades side by side as in the present invention, it is confirmed that there is no problem by analysis using numerical fluid dynamics and a wind tunnel test using a model rotor. I have confirmed. FIG. 12 is an example of an analysis model used for analysis by computational fluid dynamics. FIGS. 13A and 13B show the results of analysis using the analysis model of FIG. 12. The thrust and required power of the ducted fan alone and the thrust and required power of one ducted fan when the twin ducted type is used. The comparison with is shown. As can be seen from FIGS. 13A and 13B, the twin ducted type has no effect on the performance. In addition, the ducted fan cannot avoid energy loss due to the rotation of the air blown out of the duct due to the influence of the rotating blades, but this energy loss is also due to the twin ducted type by analysis using computational fluid dynamics. It has been confirmed that there is no influence (FIG. 14). As shown in FIG. 14, since the thrust does not change even if the rotation direction of the two fans is changed to the same direction and the opposite direction, it can be seen that the air blown out from each fan does not interfere with each other. Further, FIG. 15 shows the result of a wind tunnel test simulating the tail rotor blade of the present invention. From FIG. 15, even in the case of the twin ducted type as in the present invention, the driving torque required to obtain the same thrust is equal as compared with the case of one conventional ducted fan, and two ducted fan type tails are obtained. It can be seen that there is no performance degradation due to aerodynamic interference of the rotor blades.
3) Design of rotor system (1) Mounting two ducted fan type tail rotor blades for small helicopters that have been used in the past has little development risk. New technologies acquired through the development of small aircraft can also be adopted immediately. Therefore, by sharing the technology of the small machine and the large machine, the development cost and period can be greatly reduced. Even in aircraft, iterative design is an excellent way to reach sophisticated designs. As a result, it is possible to provide a tail rotor with low cost, light weight, high safety, and high performance.
(2) as compared with the conventional propeller type tail rotor, ducted fan-type tail rotor, the high stiffness, fatigue-empty elasticity problem is small. Therefore, safety is high, light weight and high reliability.
4) Design of drive system (1) Conventional propeller-type tail rotor blades are often attached to the upper end of a vertical tail blade in order to increase the mounting position. For this reason, it was necessary to install an intermediate gear box and bend the tail rotor blade drive shaft. In the twin ducted fan type tail rotor blade of the present invention, the lower tail rotor blade is installed at a position corresponding to the intermediate gear box, so it can also be used as this intermediate gear box, and can be used as a conventional propeller tail rotor blade. There is almost no weight increase in comparison.
(2) In the conventional propeller-type tail rotor blade, a cooling device is required for the intermediate gear box. However, in the twin ducted fan type of the present invention, the tail rotor blade itself cools the gear box, so that the cooler Is unnecessary. For this reason, there is little horsepower consumption and it is advantageous on performance. In addition, the structure is simple and easy to maintain.
(3) In the conventional propeller type tail rotor blade, the gear box must transmit 100% horsepower, but in the case of the twin ducted fan tail rotor blade of the present invention, the upper gear box is A horsepower of 50% is sufficient. Therefore, the gear box can be reduced in weight.
5) Airframe structure design In the twin ducted fan type tail rotor of the present invention, the tail boom does not have the aeroelastic requirement as in the case of a conventional propeller tail rotor, and the design is easy. Moreover, since the conventional vertical tail design for a small aircraft can be followed, the design efficiency is good and the weight can be reduced.
6) Equipment design Cost can be reduced by sharing the control of two upper and lower ducted fan type tail rotor blades.
7) Safety By individually controlling the control of the two upper and lower ducted fan type tail rotor blades, it is possible to improve the safety at the time of failure in flight or at the time of being hit by military use.
8) Manufacturing cost Cost can be reduced by producing a large number of rotor blades of the same size.
9) Operational costs Adopting ducted fan type tail rotor blades with few moving parts makes maintenance easier and reduces operational costs.
[Brief description of the drawings]
FIG. 1 is a side view showing a rotary wing aircraft equipped with a twin ducted fan type tail rotor of the present invention.
FIG. 2 is a perspective view of the twin ducted fan type tail rotor blade of the present invention as viewed from the left front.
FIG. 3 is a perspective view of the twin ducted fan type tail rotor blade of the present invention as seen from the right front side.
FIG. 4 is a structural view of the twin ducted fan type tail rotor blade of the present invention as seen from the left front.
FIG. 5 is a cross-sectional view taken along line AA in FIG. 4;
6 is a cross-sectional view taken along line BB in FIG.
7 is a cross-sectional view taken along the line CC of FIG.
FIG. 8 is a partially broken front view showing an assembled state of a ducted fan type rotor blade.
FIG. 9 is a perspective view showing an exploded state of a ducted fan type rotor blade.
FIG. 10 is a side view showing details of a gear box of a lower rotor in the twin ducted fan type tail rotor of the present invention.
11 is a cross-sectional view taken along the line DD of FIG.
FIG. 12 shows an example of an analysis model used for analysis by numerical fluid dynamics regarding the influence on performance by using ducted fans side by side.
FIGS. 13A and 13B are analysis results using the analysis model of FIG. 12, and the thrust and required power of the ducted fan alone, the thrust of one ducted fan when the twin ducted fan type is used, and This shows a comparison with the required power.
FIG. 14 shows that there is no change in thrust even if the rotation direction of two twin ducted fans is changed to the opposite direction.
FIG. 15 is a comparison of the results of a wind tunnel test simulating the twin ducted fan type tail rotor blade of the present invention with the case of one conventional ducted fan.
FIG. 16 is a side view showing a conventional large rotorcraft having a propeller-type tail rotor with a total weight of 7 tons or more.
FIG. 17 is a perspective view of a conventional small rotor blade having a ducted fan type tail rotor blade with a capacity of 5 tons or less, as viewed from the upper left front.
FIG. 18 is a side view of a large rotary wing aircraft with a ducted fan tail rotor designed for a large rotary wing aircraft.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotary wing aircraft 2 Main rotor 3 Airframe 4 Tail boom 5 Vertical tail 6,6 'Ducted fan type rotor 7 Horizontal tail 8 Drive rotary shaft 9, 9' Gear box 10 Drive shaft 11, 11 'Blade 12, 12 ′ Hub 13 Link 14 Slit 15 Output shaft 16 Hub fitting 17 Bearing 18 Pitch shaft 19 Pitch horn 20 Spider 21 Stud 22 Output shaft 23 Push rod 25 Temperature sensor 26 Spiral bevel gear 27, 28 Drive gear

Claims (7)

Two ducted fan rotors are embedded vertically in the rear end and vertical tail of the tail boom of a rotary wing aircraft, and the plurality of blades in the two ducted fan rotors are connected to the center of rotation. It is attached to the hub so that only the pitch angle can be changed,
In each ducted fan type rotor blade, the rotational driving force of the driving rotary shaft provided at the upper part of the tail boom is transmitted to the gear box of the lower rotor blade, and the rotational driving force from the gear box of the lower rotor blade is received. Is transmitted to the gear box of the upper rotor blade via the drive shaft,
A twin ducted fan type tail rotor of a rotary wing aircraft , wherein each gear box is provided at the center of rotation. The twin ducted fan tail rotor of a rotary wing aircraft according to claim 1 , wherein the number of rotations of the two ducted fan rotors is different. The twin ducted fan tail rotor of a rotorcraft according to claim 1 or 2, wherein the number of blades of the two ducted fan rotors is different. The twin ducted fan type tail rotor of a rotary wing aircraft according to claim 1 , wherein the number of rotations of the two ducted fan rotors is different and the number of blades is different. The twin ducted fan of a rotary wing aircraft according to any one of claims 1 to 4 , wherein control of two ducted fan type rotor blades is controlled by one actuator. Mold tail rotor. The twin ducted fan of a rotary wing aircraft according to any one of claims 1 to 4 , wherein control of the two ducted fan type rotor blades is controlled independently of each other. Mold tail rotor. 7. The rotorcraft according to claim 6 , wherein one rotor blade of the two ducted fan rotor blades does not generate thrust during forward flight but generates thrust only during hovering. Twin ducted fan type tail rotor.

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