U.S. patent application number 14/499618 was filed with the patent office on 2015-08-13 for cyclic pitch actuation system for counter-rotating propellers.
The applicant listed for this patent is Hamilton Sundstrand Corporation. Invention is credited to Robert H. Perkinson.
Application Number | 20150225053 14/499618 |
Document ID | / |
Family ID | 52469647 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150225053 |
Kind Code |
A1 |
Perkinson; Robert H. |
August 13, 2015 |
CYCLIC PITCH ACTUATION SYSTEM FOR COUNTER-ROTATING PROPELLERS
Abstract
A counter-rotating propeller system comprises a cyclic pitch
system connected to a first plurality of propeller blades and a
variable pitch system connected to a second plurality of propeller
blades. The first plurality of propeller blades and the second
plurality of propeller blades are configured to rotate about a
common axis.
Inventors: |
Perkinson; Robert H.;
(Stonington, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hamilton Sundstrand Corporation |
Windsor Locks |
CT |
US |
|
|
Family ID: |
52469647 |
Appl. No.: |
14/499618 |
Filed: |
September 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61939091 |
Feb 12, 2014 |
|
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Current U.S.
Class: |
416/1 ;
416/129 |
Current CPC
Class: |
B63H 3/00 20130101; B64D
2027/005 20130101; Y02T 50/60 20130101; B63H 5/10 20130101; B64C
11/306 20130101; B63H 1/20 20130101; Y02T 50/66 20130101; B64C
11/02 20130101 |
International
Class: |
B63H 5/10 20060101
B63H005/10; B63H 3/00 20060101 B63H003/00; B63H 1/20 20060101
B63H001/20 |
Claims
1. A counter-rotating propeller system comprising: a cyclic pitch
system connected to a first plurality of propeller blades; and a
variable pitch system connected to a second plurality of propeller
blades, wherein the first plurality of propeller blades and the
second plurality of propeller blades are configured to rotate about
a common axis.
2. The system of claim 1, further comprising a first hub supporting
the first plurality of propeller blades, the first hub supported
for rotation directly by a first input shaft such that the first
hub is rotatable relative to the first input shaft.
3. The system of claim 2, further comprising a second input shaft
supported by the first hub for rotation relative to the first hub
and the first input shaft.
4. The system of claim 3, further comprising a second hub
supporting the second plurality of propeller blades, the second hub
supported by the second input shaft.
5. The system of claim 4, further comprising a planetary gear train
driven by the first input shaft, the planetary gear train including
a sun gear attached for rotation with the first input shaft, at
least one planet gear supported on a planet gear carrier attached
to the second input shaft, and a ring gear defined by the first
hub, wherein the planetary gear train drives the first hub in a
first direction and the second hub in a second direction opposite
the first direction.
6. The system of claim 1, wherein the cyclic pitch system includes
a plurality of actuators configured to vary a pitch between at
least two of the first plurality of propeller blades.
7. The system of claim 6, wherein the cyclic pitch system includes
a first hoop rotatably engaging a second hoop.
8. The system of claim 7, wherein the first hoop is non-rotational
and attached to the plurality of actuators and the second hoop
rotates with the first plurality of propeller blades.
9. The system of claim 8, wherein the first hoop is attached to the
plurality of actuators with a spherical joint.
10. The system of claim 1, wherein the variable pitch system
includes an actuator disposed in a second hub configured to adjust
a pitch of the second plurality of propeller blades.
11. A method of controlling a counter-rotating propeller system
comprising: cyclically changing a pitch of a first plurality of
propeller blades with a cyclic pitch system; and variably changing
a pitch of a second plurality of propeller blades with a variable
pitch system.
12. The method of claim 11, wherein the pitch of the first
plurality of propeller blades varies depending on a circumferential
location of each of the first plurality of propeller blades.
13. The method of claim 12, wherein the pitch of the second
plurality of propeller blades is varied approximately equally.
14. The method of claim 11, wherein the cyclic pitch system
includes a first hoop rotatably engaging a second hoop and the
first hoop is non-rotational and attached to a plurality of
actuators and the second hoop rotates with the first plurality of
propeller blades.
15. The method of claim 14, wherein the variable pitch system
includes an actuator disposed in a hub configured to adjust a pitch
of the second plurality of propeller blades.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/939,091, which was filed on Feb. 12, 2014 and is
incorporated herein by reference.
BACKGROUND
[0002] Design of rotors and propellers is often quite complex. A
large number of factors must be taken into account, including
flexure of the rotor under heavy loads and the required motions of
the rotor blades with respect to the drive mechanism.
[0003] Rigid turboprop propeller systems provide collective pitch
control of the propeller blades. Pitch angles ranging from a fully
feathered minimum drag angle to pitch angles which provide reverse
thrust are typically provided to provide propeller speed and power
management along a propeller axis of rotation. Inflow angles not
along the axis of rotation due to aircraft maneuvers generate
bending moments on the propeller shaft and subsequent twisting of
the airframe. The resulting bending moments are rather large and
conventional propeller systems are rigidly structured
therefore.
[0004] Fully articulated rotors such as those of helicopters
provide cyclic and collective pitch of the rotor blades.
Articulation of the rotor disc plane vectors the rotor thrust to
provide fore, aft and lateral movement of the helicopter with
minimal bending moment of the rotor shaft. As compared to rigid
turboprop propeller systems, articulated rotor systems of a
helicopter are significantly more complex.
[0005] Prop rotors are used as both propellers and rotors in
aircraft such as a tilt rotor aircraft. A tilt rotor or tilt wing
aircraft typically employs a pair of rotor systems which are
pivotable such that the rotors may assume a vertical or horizontal
orientation. In a horizontal orientation (i.e., horizontal rotor
plane), the aircraft is capable of hovering flight, while in a
vertical orientation (i.e., vertical rotor plane), the aircraft is
propelled in the same manner as conventional propeller driven
fixed-wing aircraft. Typically, tilt rotor aircraft utilize fully
articulated rotors to provide effective hover and slow speed
control. Tilt rotor aircraft therefore provide a combination of
advantages and complexities of both fixed wing turboprop aircraft
and helicopter systems.
[0006] Accordingly, it is desirable to provide an actuation system
to incorporate cyclic pitch features into conventional rigid
mounted prop rotor systems without the complexities inherent in
fully articulated rotors.
SUMMARY
[0007] A counter-rotating propeller system comprises a cyclic pitch
system connected to a first plurality of propeller blades and a
variable pitch system connected to a second plurality of propeller
blades. The first plurality of propeller blades and the second
plurality of propeller blades are configured to rotate about a
common axis.
[0008] These and other features may be best understood from the
following drawings and specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic representation of an example
counter-rotating propeller system.
[0010] FIG. 2 is a cross-sectional view of the counter-rotating
propeller system.
[0011] FIG. 3 is a cross-sectional view of an example planetary
gear train for the counter-rotating propeller system.
DETAILED DESCRIPTION
[0012] Referring to FIG. 1, an example self-contained
counter-rotating propeller system 14 is driven by a gas turbine
engine 10 through a reduction gearbox 12. The counter-rotating
propeller system 14 drives a first plurality of propeller blades 18
in a first direction about a main axis A and a second plurality of
propeller blades 20 in an opposite direction about the axis A. The
counter-rotating propeller system 14 is covered by cowlings (also
sometimes referred to as spinners) 16A, 16B. The cowlings 16A, 16B
cover a gear train (FIG. 2) that provides the counter-rotation of
the first and second pluralities of propeller blades 18, 20. The
entire counter-rotating propeller system 14 is disposed within the
cowlings 16A, 16B and is separate from the gas turbine engine 10
and the reduction gearbox 12.
[0013] In the illustrated example, the counter-rotating propeller
system 14 requires only a first input shaft 22 (FIG. 2) from the
gas turbine engine 10. A desired differential rotation is provided
by the gear train enclosed within the cowlings 16A, 16B. The
differential rotation is provided by the torque split through the
gear train which provides approximately equal but opposite torque
to the first and second plurality of propeller blades 18, 20.
Alternatively, torque split could be non-equally allocated between
the first and second plurality of propeller blades 18, 20.
[0014] Referring to FIG. 2, the example counter-rotating propeller
system 14 includes a first hub 26 that supports the first plurality
of propeller blades 18 and is supported about the first input shaft
22. The first input shaft 22 includes a flange 24 that provides for
securing the first input shaft 22 to the reduction gearbox 12. No
other driving connection is required between the reduction gearbox
12 and the counter-rotating propeller system 14.
[0015] The first hub 26 includes bearings 28 that support the first
hub 26 for rotation about the first input shaft 22. The first hub
26 is supported on the first input shaft 22 by the bearings 28 but
is rotatable independent of rotation of the first input shaft 22. A
second input shaft 34 is supported within the first hub 26 by
bearings 32 and is rotatable independent of both the first hub 26
and the first input shaft 22.
[0016] A second hub 30 is attached to the second input shaft 34 and
rotates with the second input shaft 34. The first input shaft 22
provides the driving input to an example planetary gear train 38.
The planetary gear train 38 includes a sun gear 40 that is mounted
to the first input shaft 22. The sun gear 40 is driven by and at
the same speed as the first input shaft 22. The sun gear 40 is
surrounded by a plurality of planet gears 42 that are supported on
a planet carrier 44. The planet carrier 44 is in turn supported by
a flange 36 of the second input shaft 34. The planet gears 42 in
turn drive a ring gear 46. The ring gear 46 is defined on an inner
surface of the first hub 26 and drives rotation of the first hub
26.
[0017] Referring to FIG. 3 with continued reference to FIG. 2, the
planetary gear train 38 operates by driving the sun gear 40 with
the first input shaft 22. The sun gear 40 drives the planet gears
42 through the meshing engagement there between. Because the planet
gears 42 are supported by the planet carrier 44 which is mounted to
the second input shaft 34, the second input shaft 34 will rotate in
a direction indicated by arrow 50 common with rotation of the first
input shaft 22.
[0018] The planet gears 42 themselves rotate in a direction
opposite that of the sun gear 40 and translate that motion to the
ring gear 46. The translated motion to the ring gear 46 will result
in the first hub 26 rotating in a direction indicated by arrow 48
about the axis A. The second input shaft 34 will rotate in the
direction indicated by the arrow 50 about the sun gear 40 and
thereby drive the second hub 30 in a direction opposite that of the
first hub 26 about the axis A.
[0019] Because the planetary gear train 38 comprises the first hub
26 and the second input shaft 34, the planetary gear train 38 is
housed entirely within the counter-rotating propeller system 14.
Therefore, implementation of the planetary gear train 38 does not
require additional modifications to the reduction gearbox 12 which
is driven by the gas turbine engine 10.
[0020] A pitch angle of each of the first and second plurality of
propeller blades 18, 20 is variable to optimize performance and
allow the counter-rotating propeller system 14 to provide a
directional influence on an airframe of an aircraft, such as a
fixed wing or hovering aircraft. Changes in pitch angle in the
first plurality of propeller blades 18 can be made independently
from changes in pitch angle of the second plurality of propeller
blades 20.
[0021] In the illustrated example of FIG. 2, a cyclic pitch
actuation system 60 provides cyclic pitch variations to the first
plurality of propeller blades 18. The cyclic pitch actuation system
60 includes cyclic pitch actuators 62 connected to the first
plurality of propeller blades 18 by a first linkage 64. Although
only two cyclic pitch actuators 62 are shown in the drawings, three
or more cyclic pitch actuators 62 could be placed around a
circumference of the reduction gearbox 12.
[0022] The cyclic pitch actuators 62 can be activated independently
of each other to provide a varied cyclic pitch to the first
plurality of propeller blades 18 depending on the circumferential
location of the each of the first plurality of propeller blades 18.
The cyclic pitch actuators 62 cause the first plurality of
propeller blades 18 to rotate about an axis 52 relative to the
first hub 26 on bearings 66.
[0023] In the illustrated example, the first linkage 64 includes a
non-rotating hoop 68, a rotating hoop 70, and a cam arm 72. The
non-rotating hoop 68 includes an arm 74 that forms a socket 76 at a
distal end to accept a spherical end 78 on an actuator rod 80 of
the cyclic pitch actuator 62 to form a spherical joint. The
spherical joint increase the freedom of movement between the
non-rotating hoop 68 and the cyclic pitch actuators 62. The
increased freedom of movement from the spherical joint allows an
axis of the non-rotating hoop 68 and the rotating hoop 70 to be
non-parallel with the axis A of the first and second plurality of
propeller blades 18, 20. The non-rotating hoop 68 also includes an
outer race 82 that supports bearings 84 on a radially inner
side.
[0024] The rotating hoop 70 includes an inner race 86 that supports
the bearings 84 on a radially outer side and rotates with the first
plurality of propeller blades 18. The rotating hoop 70 is attached
to each of the first plurality of propeller blades 18 through the
cam arm 72. The cam arm 72 is rotatably attached to the rotating
hoop 70 about an axis that extends approximately tangential to a
circumference of the rotating hoop 70. The cam arm 72 is rotatably
attached to the first plurality of propeller blades 18 about an
axis that is generally perpendicular to the axis of the rotating
hoop 70.
[0025] The cyclic pitch actuation system 60 changes the cyclic
pitch of the first plurality of propeller blades 18 by extending or
retracting one or more of the cyclic pitch actuators 62 to change
an axial location of the non-rotating hoop 68 and the rotating hoop
70. When the axial location of the non-rotating hoop 68 and the
rotating hoop 70 changes, the pitch of each of the first plurality
of propeller blades 18 changes in a circumferential region adjacent
the cyclic pitch actuator 62 that moved. Therefore, as the first
plurality of propeller blades 18 rotate in a cycle, the pitch of
each of the blades can change based on the circumferential location
of the individual blades such that the pitch angle among the first
plurality of propeller blades 18 in not uniform.
[0026] In operation, the counter-rotating propeller system 14
generates a once per revolution (1P) variation in blade load by
having a non-uniform cyclic pitch controlled by a controller 90.
The controller 90 is configured to position the cyclic pitch
actuators 62 to produce a moment about the axis A. While an axis of
the thrust vector remains perpendicular to the plane of the first
plurality of propeller blades 18, the variation in blade load
creates a bending moment along the axis A which appears fixed in
relation to the aircraft. Such 1P variations may occur during
aircraft maneuvering when inflow angles are not on the propeller
axis A of rotation.
[0027] The conventional blade mounting arrangements accommodate
these off axis forces by rigidly mounting propeller blades to a hub
to prevent flapping and rigidly mount the first input shaft 22 to
the reduction gearbox 12. Off-axis forces are thereby transmitted
directly from the first plurality of propeller blades 18 to the
airframe.
[0028] The present invention advantageously utilizes this
conventional mounting arrangement to generate aircraft attitude
control through generation of a moment about the axis A. Movement
of the cyclic pitch actuators 62 can provide a moment in any
angular direction while the linear deflection of the cyclic pitch
actuators 62 generates a magnitude of propeller thrust.
Alternatively, it should be noted that the cyclic pitch actuation
system 60 can also operate with the cyclic pitch actuators 62
moving in unison such that the first plurality of propeller blades
18 can function as a tradition variable pitch system.
[0029] The second plurality of propeller blades 20 include a
variable pitch system 100. In the illustrated example, a pitch of
the second plurality of propeller blades 20 varies in approximate
unison. The variable pitch system 100 includes a hydraulic pitch
change actuator 102 in communication with an oil transfer tube 104.
Oil supplied through the oil transfer tube 104 is metered by a
pitch change actuator piston 106 to hydraulically operate a linkage
108 of the variable pitch system 100 to change the pitch of each of
the second plurality of propeller blades 20 to provide a desired
amount of thrust.
[0030] The preceding description is exemplary rather than limiting
in nature. Variations and modifications to the disclosed examples
may become apparent to those skilled in the art that do not
necessarily depart from the essence of this disclosure. The scope
of legal protection given to this disclosure can only be determined
by studying the following claims.
* * * * *