Rotor blade with a rotary spoiler

A rotor blade is provided with rotary spoilers rotatably supported in recesses formed in a blade body, respectively, so that the upper surface of each rotary spoiler serves as a portion of the wind surface of the rotor blade. Each rotary spoiler is turned so as to protrude from the wing surface of the blade body to make the rotary spoiler exercise its function when the rotor blade is turned to an appropriate rotary angular position to control noise and vibrations by changing the lift of the rotor blade. Each rotary spoiler is driven for turning by a driving mechanism having a driving member made of a piezoelectric material, and the operation of the driving mechanism is controlled by a controller.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a rotor blade provided with rotary 
spoilers and capable of controlling to reduce noise and vibration by 
disturbing airstream around the wing surface of the rotor blade to vary a 
lift of the rotor blade. 
2. Description of the Related Art 
Referring to FIG. 7, a helicopter is controlled to fly by a mechanical 
linkage 14 of a rotor 13, including an upper swash plate 10, a lower swash 
plate 11 and a pitch link 12. Efforts have been made to meet progressively 
increasing demand for reducing vibration and noise of the helicopter 
through the research and development of techniques for actively 
controlling a pitch of the rotor 13 in a higher frequency range. 
U.S. Pat. No. 4,519,743 discloses a technique called an individual blade 
control method (IBC method) which is intended to achieve a high level 
control through not a swash plate but a hydraulic control of the 
respective rotor blade at the base end of each rotor blade. As mentioned 
in U.S. Pat. No. 5,224,826 studies have started from a rotor provided with 
a flap using a piezoelectric material, capable of efficiently working 
under the influence of a high centrifugal force, and having a better 
responsibility (responseability) beyond the limit of responsibility by the 
hydraulic control. 
If the flight of the helicopter is controlled through the swash plates and 
the pitch link, the rotor generates vibratory force which vibrates the 
airframe of the helicopter, the lift of the rotor blades is caused to vary 
periodically according to rotation angle by the relation between the 
flying direction of the helicopter and the rotary angular position of the 
rotor blades, and the combined air vibrating effect of the rotor blades is 
exerted on the airframe to produce complex vibrational environment. FIG. 8 
and 9 show a lift distribution on the rotor blade of the rotor 13 of the 
helicopter when the rotor blade is turning (rotating) in the flying 
direction of the helicopter and a lift distribution on the same rotor 
blade when the rotor blade is turning in a direction opposite to the 
flying direction thereof. 
The control of vibrations through the direct, active control of the swash 
plate and the pitch link makes the complicated mechanical linkage more 
complicated, is practically disadvantageous in respect of weight and 
reliability, is capable of controlling only lower order of vibrations, and 
is incapable of satisfactorily effectively controlling the vibration 
generated by a rotor having four or more rotor blades. 
The IBC method needs a rotating system including high-capacity hydraulic 
actuators for moving the rotor blades individually on a mast, which 
unavoidably increases the weight and makes the mast assembly complicated. 
The control operation of the IBC method which twists the whole rotor 
blades is not necessarily efficient. 
The rotor provided with a flap is able to vary an effective portion with 
respect to the direction of a span or to control the effective portion 
partially. However, the rotor provided with a flap needs electrical 
control to achieve higher response. Since a large centrifugal force acts 
on a tip portion of the rotor blade, it is difficult to dispose a heavy 
device, such as a hydraulic actuator, on the tip portion of the rotor 
blade, and it is desirable to use a smart material, such as a 
piezoelectric material. However, piezoelectric materials can be strained 
only very slightly and hence an additional mechanism for amplifying the 
strain is necessary. If a flap is combined with the trailing edge of the 
rotor blade, small and lightweight flap hinges designed to exert only a 
low frictional resistance against the movement of the flap must be used. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the foregoing problems and 
it is therefore an object of the present invention to provide a rotor 
blade provided with a rotary spoiler, capable of controlling to reduce 
noise and vibration by disturbing airstream around the wing surface 
thereof to vary lift by rotating the rotary spoiler. 
According to one aspect of the present invention, a rotor blade comprises a 
blade body having a wing surface, one or a plurality of rotary spoilers 
each having a surface forming a portion of the wing surface of the blade 
body and rotatably supported on the blade body, and rotatably driving 
means for driving the rotary spoilers. The rotary spoiler is turned to a 
rotary angular position at which the upper surface of the rotary spoiler 
protrudes from the wing surface to vary the lift of the blade body by 
disturbing airstream around the wing surface so that noise and vibration 
caused by aerodynamic force may be controlled. 
In the rotor blade of the present invention, the turning axis of the rotary 
spoiler may be inclined to a line perpendicular to a chord line of the 
blade body to make the height of a portion of the rotary spoiler 
protruding from the wing surface variable for the further effective 
control of noise and vibration caused by aerodynamic force. 
In the rotor blade of the present invention, the driving means for driving 
the rotary spoiler may comprise an ultrasonic motor. Since energy can be 
easily supplied to the ultrasonic motor through a slip ring included in a 
rotor assembly, and a wiring line connected to the ultrasonic motor, a 
mechanism including the rotary spoiler has a simple construction. 
In the rotor blade of the present invention, the blade body may be provided 
with a plurality of rotary spoilers between a middle portion of the 
longitudinal blade body and an outer end thereof, and the times for making 
the rotary spoilers protrude from the wing surface and the respective 
rotary angular positions of the plurality of rotary spoilers may be 
simultaneously or individually controlled to achieve a control of a larger 
aerodynamic force and a desired control of aerodynamic force when the 
blade body is at a desired rotary angular position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a rotor blade 1 in a first embodiment according to the 
present invention for a two-blade rotor for a helicopter has a 
longitudinal blade body, and two rotary spoilers 2 arranged at positions 
near the trailing edge of the rotor blade 1, that is, at portions of the 
blade body between a middle portion C of the longitudinal blade body and 
an outer end E thereof, in which the rotary spoilers 2 are expected to 
exercise their aerodynamic functions effectively. The rotary spoiler 2 is 
arranged longitudinally at a predetermined or optional interval. 
Referring to FIG. 3, each of the rotary spoilers 2 is supported for 
rotation in an upper recess 4, which is formed in a mounting portion 3 of 
the blade body of the rotor blade 1 opening in the wing surface 1a of the 
rotor blade 1. The rotary spoiler 2 is a disk having a substantially 
triangular cross section and an upper surface 2a smoothly merging into the 
wing surface 1a of the rotor blade 1. When the rotary spoiler 2 is at a 
rotary angular position shown in FIG. 3, the upper surface 2a of the 
rotary spoiler 2 serves as a portion of the wing surface 1a. In this 
embodiment, a chord length of the rotor blade 1 is 400 mm and the diameter 
of the rotary spoilers 2 is about 40 mm. The mounting portion 3 of the 
blade body of the rotor blade 1 has a lower recess 5 corresponding to the 
upper recess 4. An ultrasonic motor 6 is disposed in the lower recess 5, 
the output shaft 7 of the ultrasonic motor 6 is extended through a wall 3a 
between the upper recess 4 and the lower recess 5 into the upper recess 4 
and is connected to the rotary spoiler 2 disposed in the upper recess 4. 
The ultrasonic motor 6 is disposed so that the turning axis of the output 
shaft 7 thereof is inclined to the wing surface 1a and substantially 
perpendicular to the chord line of the rotor blade 1. The ultrasonic motor 
6 has a driving member made of a piezoelectric material. The ultrasonic 
motor 6 has satisfactory response characteristics (responseability) and is 
capable of properly functioning under a high centrifugal force. The 
ultrasonic motor 6 is connected to a controller 9. 
Each rotary spoiler 2 is moved between a rotary angular position where the 
rotary spoiler 2 is in a concealed state shown in FIG. 3 and a rotary 
angular position where the rotary spoiler 2 is in a protruded state shown 
in FIG. 4. When the rotary spoiler 2 is in the concealed state shown in 
FIG. 3, the upper surface 2a of the rotary spoiler 2 merges smoothly into 
the wing surface 1 a of the rotor blade 1 and forms a portion of the wing 
surface 1a, so that the wing surface 1a of the rotor blade 1 has a normal 
shape. When the rotary spoiler 2 is in the protruded state shown in FIG. 
4, the upper surface 2a of the rotary spoiler 2 protrudes from the wing 
surface 1a of the rotor blade 1 to exercise its function as a spoiler for 
disturbing airstreams around the wing surface 1a. When airstreams around 
the wing surface 1a, i.e., the lifting surface, are thus disturbed by the 
rotary spoiler 2, the disturbance of the airstreams affect the lift of the 
rotor blade 1 directly, so that an aerodynamic force generated by the 
rotor blade 1 is controlled. The aerodynamic force generated by the rotor 
blade 1 can be controlled by the ultrasonic motors 6 to rotate the 
plurality of rotary spoilers 2 continuously or stepwise, and 
simultaneously or in different phases according to the rotary angular 
position of the rotary blade 1. 
When controlling the two-blade rotor at a frequency twice the rotating 
speed of the two-blade rotor, a method of controlling the aerodynamic 
force generated by the rotor blade 1 drives the two rotary spoiler 2 for 
continuous rotation at a rotating speed equal to the rotating speed of the 
two-blade rotor with a phase difference of 180.degree. between the rotary 
angular positions of the rotary spoilers according to the rotary angular 
position of the rotor blade 1. One of the two rotary spoilers 2 is set in 
the protruded state when the rotor blade 1 is on the front side with 
respect to the flying direction of the helicopter, and the other rotary 
spoiler 2 is set in the protruded state when the rotor blade 1 is on the 
back side with respect to the flying direction of the helicopter as shown 
in FIG. 6. Thus, each of the two rotary spoilers 2 is set once in the 
protruded state for every one turn of the rotor blade 1 and hence the 
rotor blade 1 can be controlled at a frequency twice the rotating speed of 
the two-blade rotor. The respective positions of the rotary spoilers 2 on 
the blade body of the rotor blade 1 and the mode of rotation of the rotary 
spoilers 2 are determined on the basis of the previously determined 
vibration mode of the rotor blade 1 at the frequency of a vibration in 
question. More specifically, the rotary spoilers 2 are disposed in a 
portion of the blade body corresponding to the loop of the vibration mode 
of the blade body of the rotor blade 1, and the controller 9 actuate each 
ultrasonic motor 6 for driving each rotary spoiler 2 so that the rotary 
spoiler 2 is protruded to its highest position at a rotary angular 
position of the rotor blade 1 where a magnitude of the vibration mode 
increases to a maximum. 
If the rotor blade 1 is employed in a four-blade rotor and the four-blade 
rotor is controlled at a frequency four times the rotating speed of the 
four-blade rotor, the phases of rotation of the four rotary spoilers 2 are 
differentiated at a phase difference of 90.degree. to protrude each of the 
four rotary spoilers 2 once for every one turn of the rotor blade 1. The 
respective positions of the rotary spoilers 2 on the blade body of the 
rotor blade 1 and the mode of rotation of the rotary spoilers 2 are 
determined by the same method as that applied to the two-blade rotor. 
It is known that the most offensive noise generated by the helicopter is 
sounds (noises) which are generated when the rotor blade 1 crosses air 
vortices generated by the preceding rotor blade 1. Therefore, noise and 
vibration caused by aerodynamic force can be controlled by disposing the 
rotary spoilers 2 at a position of the blade body of the rotor blade 1 
which crosses the vortices generated by the preceding rotor blade 1, and 
controlling the ultrasonic motors 6 by the controller 9 so that each 
rotary spoiler 2 is protruded at a moment the rotor blade 1 passes the 
vortices to locally vary the vortices generated by the preceding rotor 
blade 1 by the rotary spoiler 2. 
The foregoing aerodynamic performance of the rotor blade 1 can be expected 
even if the rotor blade 1 is provided with a single rotary spoiler 2 at a 
position on the blade body where the amplitude of a low-order vibration of 
the rotor blade 1 is a maximum instead of the plurality of rotary spoilers 
2. 
FIG. 5 shows a rotor blade 1 in a second embodiment according to the 
present invention provided with rotary spoilers 2. Each of the rotary 
spoilers 2 is rotatably supported about an turning axis inclined to a line 
perpendicular to a chord line of the blade body of the rotor blade 1 so 
that the rotary spoiler 2 can be protruded more greatly than the rotary 
spoiler 2 of the first embodiment from the wind surface of the rotor blade 
1. 
As is understood from the foregoing description according to the present 
invention, the rotor blade is provided with the rotary spoilers rotatably 
supported on the blade body thereof so as to be turned by the ultrasonic 
motors serving as driving means so that the rotary spoilers are protruded 
from the wing surface of the rotor blade to change the lift of the rotor 
blade directly by disturbing airstreams around the wind surface. Thus, the 
aerodynamic force generated by the rotor blade is controlled to reduce the 
noise and the vibration generated by the aerodynamic force. 
The ultrasonic motors serving as the driving means enable the highly 
accurate control of the rotary spoilers. Since energy can be supplied 
through the slip ring and the wiring lines to the ultrasonic motors, 
structures associated with the rotary spoilers have a simple construction. 
The rotor blade is provided with the plurality of rotary spoilers between 
the middle portion of the longitudinal blade body and the outer end 
thereof, and the plurality of rotary spoilers are controlled 
simultaneously and/or individually. Each of the rotary spoilers can be 
made to protrude when the rotor blade is at an appropriate rotary angular 
position, so that the control of greater aerodynamic force and the 
delicate control of the rotary spoilers are made by the rotary spoilers 
protruding at a rotary angular position of the rotor blade where the 
change of the aerodynamic force is desirable. 
Since the rotary spoilers are rotatably supported on the blade body of the 
rotor blade with the turning axis inclined to a line perpendicular to the 
chord line of the blade body of the rotor blade, the height of each rotary 
spoiler protruded from the wing surface can be easily changed for the 
further effective control of the aerodynamic force. 
Although the invention has been described in its preferred form with a 
certain degree of particularity, obviously many changes and variations are 
possible therein. It is therefore to be understood that the present 
invention may be practiced otherwise than as specifically described herein 
without departing from the scope and spirit thereof.