U.S. patent application number 10/939422 was filed with the patent office on 2007-08-30 for power transmission arrangement.
Invention is credited to David C. Butt, David A. Edwards, Geoffrey E. Kirk, Alan R. Maguire, Martyn Richards.
Application Number | 20070199331 10/939422 |
Document ID | / |
Family ID | 34196263 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070199331 |
Kind Code |
A1 |
Maguire; Alan R. ; et
al. |
August 30, 2007 |
Power transmission arrangement
Abstract
A power transmission arrangement comprises a first power
transmission member connectable to a first main shaft of an engine.
The arrangement also includes a second power transmission member
connectable to a second main shaft of the engine and to a third
power transmission member. A coupling assembly is provided which
has a selectable coupling condition to couple the first power
transmission member to the second power transmission member to
allow power to be transmitted from the third power transmission
member to the first main shaft of the engine via the first power
transmission member. The coupling assembly has a decoupling
condition to decouple the first power transmission member from the
second power transmission member to allow power to be transmitted
from the main shaft of the engine to the third power transmission
member via the second power transmission member.
Inventors: |
Maguire; Alan R.; (Findern,
GB) ; Butt; David C.; (Breaston, GB) ;
Richards; Martyn; (Burton-on-trent, GB) ; Kirk;
Geoffrey E.; (Loughborough, GB) ; Edwards; David
A.; (Derby, GB) |
Correspondence
Address: |
MANELLI DENISON & SELTER
2000 M STREET NW SUITE 700
WASHINGTON
DC
20036-3307
US
|
Family ID: |
34196263 |
Appl. No.: |
10/939422 |
Filed: |
September 14, 2004 |
Current U.S.
Class: |
60/796 |
Current CPC
Class: |
Y10S 74/05 20130101;
F02C 7/268 20130101; F02C 7/36 20130101; F02C 7/275 20130101; F02C
3/107 20130101; F02C 7/27 20130101 |
Class at
Publication: |
060/796 |
International
Class: |
F02C 7/20 20060101
F02C007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2003 |
GB |
0321952.4 |
Mar 17, 2004 |
GB |
0405943.2 |
Claims
1. A power transmission arrangement comprising a first power
transmission member connectable to a first power assembly of a
drive arrangement, a second power transmission member connectable
to a second power assembly of a drive arrangement and to a third
power transmission member, characterised by a coupling assembly
having a selectable coupling condition to couple the first power
transmission member to the second power transmission member to
allow power to be transmitted from the third power transmission
member to the first power assembly via the first power transmission
member, and having a selectable decoupling condition to decouple
the first power transmission member from the second power
transmission member to allow power to be transmitted from the
second power assembly to the third transmission member via the
second transmission member.
2. A power transmission arrangement according to claim 1 wherein
the coupling assembly is mounted on the first and second power
transmission members.
3. A power transmission arrangement according to claim 1 wherein
the coupling assembly comprises a fluid operated clutch.
4. A power transmission arrangement according to claim 1 wherein
the coupling assembly comprises a main body, having first and
second parts movable relative to each other.
5. A power transmission arrangement according to claim 4 wherein
the second power transmission member comprises a connection member
to drivingly connect the third power transmission member
thereto.
6. A power transmission arrangement according to claim 5 wherein
the connection member comprises a gear to drivingly connect the
third power transmission member to the second transmission
member.
7. A power transmission arrangement according to claim 5 or 6
wherein the second power transmission member extends through the
main body to said connection member.
8. A power transmission arrangement according to claim 7 wherein
the first part comprises a first fluid chamber, and the second part
comprises a second fluid chamber, the first and second parts being
in fluid communication with each other.
9. A power transmission arrangement according to claim 8 wherein
each of the first and second fluid chambers is of an annular
configuration.
10. A power transmission arrangement according to claim 9 wherein
each of the first and second fluid chambers is of a toroidal
configuration.
11. A power transmission arrangement according to claim 9 wherein
the main body has a configuration of a torus defining a space to
receive at least one of said first and second power transmission
members.
12. A power transmission arrangement according to claim 11 wherein
the space receives both of said first and second power transmission
members and the second power transmission member extends wholly
through the aforesaid space.
13. A power transmission arrangement according to claim 8 wherein
each of the chambers includes a plurality of radially extending
vanes.
14. A power transmission arrangement according to claim 4 wherein
the main body includes drain means to allow fluid in the main body
to drain there from.
15. A power transmission arrangement according to claim 14 wherein
the drain means comprises a drain aperture or a plurality of drain
apertures defined in the main body, the, or each, drain aperture
being defined in a region between the first and second
chambers.
16. A power transmission arrangement according to claim 8 wherein
the coupling assembly comprises an enclosure in which the main body
is arranged, and fluid from the main body can drain into the
enclosure.
17. A power transmission arrangement according to any of claims 8
to 16 wherein the coupling assembly comprises a fluid supply system
to supply fluid to the main body.
18. A power transmission arrangement according to claim 17 wherein
the fluid supply system is arranged to supply fluid to the main
body via the central member extending into, or through, said
central space.
19. A power transmission arrangement according to claim 17 wherein
the fluid supply system is arranged to supply to the main body
externally of the central space.
20. A power transmission arrangement according to claim 19 wherein
the fluid supply is supplied through one or more fluid supply holes
in the main body.
21. A power transmission arrangement according to claim 4 wherein
the first part is fixedly mounted on the first power transmission
member, and the second part is fixedly mounted on the second power
transmission member.
22. A power transmission arrangement according to claim 1 wherein
the first and second power transmission members comprise shafts,
arranged coaxially relative to each other.
23. A power transmission arrangement according to claim 22 wherein
the second power transmission member is arranged within the first
power transmission member.
24. A power transmission arrangement according to claim 1 wherein
the coupling assembly is offset from the first and second power
transmission member and is connected to the first and second power
transmission members by at least one ancillary gear
arrangement.
25. A drive arrangement comprising first and second power
assemblies and a power transmission arrangement according to any
preceding claim, wherein the first power assembly is connected to
the first power transmission member, and the second power assembly
is connected to the second power transmission member.
26. A drive arrangement according to claim 25 wherein the first
power assembly comprises a first compressor, a first turbine and a
first torque transmitter to transmit torque to the first compressor
form the first turbine, and the second power assembly comprises a
second compressor, a second turbine and a second torque transmitter
to transmit torque from the second turbine to the second
compressor, the first power transmission member being connected to
the first torque transmitter and the second power transmission
member being connected to the second torque transmitter.
27. A drive arrangement according to claim 25 further including a
starter for starting the drive arrangement, wherein the power
transmission arrangement can couple together the first and second
power transmission members during starting, whereby the starter can
turn both of the first and second torque transmitters during the
aforesaid starting of the drive arrangement, and can decouple the
first and second torque transmitters after the aforesaid starting
to permit independent operation of the first and second power
assemblies.
28. A drive arrangement according to claim 27 wherein the starter
is connected to the third power transmission member to drive the
first and second torque transmitters during the aforesaid
starting.
29. A drive arrangement according to claim 25 including power
receiving means connected to the second torque transmitter, and the
second torque transmitter drives the power receiving means after
decoupling of the first and second torque transmitters from each
other.
30. A gas turbine engine incorporating a drive arrangement
according to claim 25 wherein the first compressor comprises a high
pressure compressor, the first turbine comprises a high pressure
turbine, and the first torque transmitter comprises a first main
shaft interconnecting the high pressure compressor and turbine.
31. A gas turbine engine incorporating a drive arrangement
according to claim 25 wherein the second compressor comprises an
intermediate pressure compressor, the second turbine comprises an
intermediate pressure turbine, and the second torque transmitter
comprises a second main shaft interconnecting the intermediate
pressure compressor and turbine.
32. A coupling assembly comprising a main body having a first part
selectively coupled by fluid to a second part, the first part being
mountable on a first power transmission member and the second part
being mountable on a second power transmission member, the main
body defining a space to receive at least one of the power
transmission members, and the coupling assembly further comprising
fluid supply means for supplying fluid to the main body via a
region of the main body outside the aforesaid space.
33. A coupling assembly according to claim 32 wherein the fluid is
a hydraulic fluid, the first part comprises a first fluid chamber
and the second part comprises a second fluid chamber.
34. A coupling assembly according to claim 33 wherein each of the
first and second fluid chambers is of an annular configuration.
35. A coupling assembly according to claim 34 wherein each of the
first and second fluid chambers is of a toriodal configuration,
each of the aforesaid toroids being defined by a semi-circle.
36. A coupling assembly according to claim 32 wherein the main body
has a configuration of a torus defining said space, the space being
a central space of the torus.
37. A coupling assembly according to claim 36 wherein the space can
receive the second power transmission member, which can extend
wholly through the space.
38. A coupling assembly according to claim 32 wherein each of the
fluid chambers includes a plurality of radially extending
vanes.
39. A coupling assembly according to claim 32 wherein the main body
includes drain means to allow fluid in the main body to drain
therefrom.
40. A coupling assembly according to claim 39 wherein the drain
means comprises a drain aperture or a plurality of drain apertures
defined in the main body and the, or each, drain aperture is
defined in a region between the first and second chambers.
41. A coupling assembly according to claim 39 wherein the coupling
assembly includes an enclosure in which the main body is arranged,
and fluid from the main body can drain into the enclosure.
Description
[0001] This invention relates to power transmission arrangements.
More particularly, but not exclusively, the invention relates to
power transmission arrangements for use in engines, such as gas
turbine engines. More particularly, but not exclusively, the
invention relates to power transmission arrangements for providing
start up power to a gas turbine engine and taking power from a main
shaft of a gas turbine engine.
[0002] In modern aircraft, there is generally an increased
requirement for electric power. Typically, power can be taken from
the main shafts of the engine. Also, it is necessary to provide
power to an engine during start up.
[0003] According to one aspect of the invention, there is provided
a power transmission arrangement comprising a first power
transmission member connectable to a first main shaft of an engine,
a second power transmission member connectable to a second main
shaft of an engine and to a third power transmission member, and a
coupling assembly having a coupling condition to couple the first
power transmission member to the second power transmission member
to allow power to be transmitted from the third power transmission
member to the first main shaft of an engine via the first power
transmission member, and having a selectable decoupling condition
to decouple the first power transmission member from the second
power transmission member to allow power to be transmitted from the
second main shaft of the engine to the third power transmission
member via the second transmission member.
[0004] According to another aspect of this invention, there is
provided a power transmission arrangement comprising a first power
transmission member connectable to a first main shaft of an engine,
a second power transmission member connectable to a second main
shaft of an engine and to a third power transmission member,
characterised by a coupling assembly having a selectable coupling
condition to couple the first power transmission member to the
second power transmission member to allow power to be transmitted
from the third power transmission member to the first main shaft of
the engine via the first power transmission member, and having a
selectable decoupling condition to decouple the first power
transmission member from the second power transmission member to
allow power to be transmitted from the second main shaft of the
engine to the third power transmission member via the second
transmission member. The coupling condition may comprise a
selectable coupling condition.
[0005] Preferably the coupling assembly is mounted on the first and
second power transmission members.
[0006] In a first embodiment, the coupling assembly may comprise a
fluid operated coupling. Conveniently, the coupling assembly
comprises a hydraulic clutch.
[0007] In the first embodiment, the coupling assembly may comprise
a main body, which may have first and second parts. The first and
second parts are preferably movable relative to each other. The
first part may comprise a first fluid chamber, and the second part
may comprise a second fluid chamber. The first and second fluid
chambers are preferably in fluid communication with each other. The
first part is preferably mounted on the first power transmission
member. The second part is preferably mounted on the second power
transmission member.
[0008] The first and second power transmission members may comprise
shafts. The first and second power transmission members may be
arranged coaxially of each other. Preferably, the second power
transmission member is arranged within the first power transmission
member. A second power transmission member may comprise a
connection member to drivingly connect the third power transmission
member thereto. Preferably, the connection member comprises a gear
arrangement to drivingly connect the third power transmission
member to the second transmission member.
[0009] Preferably, the second power transmission member extends
through the coupling assembly to said connection means.
[0010] In one embodiment, the coupling assembly may be mounted on
the first and second power transmission members and may be co-axial
therewith.
[0011] In another embodiment, the coupling assembly may be offset
from the first and second power transmission members and may be
connected to the first and second power transmission members by
ancillary gear arrangements. The first part of the coupling
assembly may be connected by a first ancillary gear arrangement to
the first power transmission member. The second part of the
coupling assembly may be connected by a second ancillary gear
arrangement to the second power transmission member.
[0012] The third power transmission member may extend from the
coupling assembly. Preferably, the third power transmission member
is fixedly attached to the first coupling assembly, and is
conveniently fixedly attached to the second part of the coupling
assembly.
[0013] Each of the first and second fluid chambers may be of an
annular configuration. Preferably, each of the first and second
fluid chambers is of a toroidal configuration. Each of the
aforesaid toroids may be defined by a semi-circle. Preferably, the
main body has a configuration of a torus defining a space which may
receive at least one of said power transmission members.
Preferably, the power transmission member comprises the second
power transmission member. The space may receive both of said power
transmission members. The second power transmission member may
extend wholly through the aforesaid space.
[0014] Each of the chambers preferably includes a plurality of
vanes, which may be radially extending vanes.
[0015] The main body may include drain means to allow fluid in the
main body to drain therefrom. Preferably, the drain means comprises
a drain aperture or a plurality of drain apertures defined in the
main body. The, or each, drain aperture may be defined to a region
between the first and second chambers.
[0016] The coupling assembly may comprise an enclosure in which the
main body is arranged. Preferably, fluid from the main body can
drain into the enclosure.
[0017] The coupling assembly may comprise a fluid supply system to
supply fluid to the main body. The fluid supply system may be
arranged to supply fluid to the main body via the central member
extending into, or through, said space in the main body.
[0018] Alternatively, fluid supply system may be arranged to supply
fluid to the main part externally of the central space. Preferably,
the fluid supply is supplied through one or more fluid supply holes
in the main body.
[0019] In a second embodiment, the coupling assembly may comprise a
friction clutch. The friction clutch may comprise a first clutch
member mounted on the first power transmission member, and a second
clutch member mounted on the second power transmission member.
[0020] The first clutch member may comprise a first clutch plate.
The second clutch member may comprise a second clutch plate.
[0021] The first clutch member may comprise a driven clutch member,
and the second clutch member may comprise a driving clutch member,
the first clutch member being driven by the second clutch
member.
[0022] The friction clutch may further comprise force applying
means to apply a force to at least one of the first and second
clutch members, to move the first and second clutch members
relative to each other into engagement with each other whereby the
second clutch member can drive the first clutch member. Preferably,
the force applying means can apply the aforesaid force to the
second clutch member.
[0023] The force applying means may comprise a piston arrangement.
The piston arrangement may comprise a fluid receiving part to
receive a fluid, such as hydraulic fluid, to apply a force to move
the first and second clutch members relative to each other into
engagement with each other.
[0024] The fluid receiving part may comprise a chamber to receive
said fluid.
[0025] The friction clutch may comprise disengaging means to
disengage the first and second clutch members from each other.
[0026] The disengaging means may comprise a second fluid receiving
part to receive a fluid, such as a hydraulic fluid to move the
first and second clutch members away from each other.
[0027] The second fluid receiving part may comprise a second
chamber to receive said fluid.
[0028] Alternatively, the disengaging means may comprise a spring
arrangement to move the first and second clutch members away from
each other.
[0029] The friction clutch may comprise a bearing arranged between
the force applying means and the first or second clutch members.
Preferably the bearing is arranged between the force applying means
and the second clutch member. The bearing may be connected to the
force applying means and the first or second clutch member.
Alternatively, the bearing may be connected to one of the force
applying means and the first or second clutch member, thereby
engaging the other when said force is applied.
[0030] The bearing may comprise a thrust bearing.
[0031] The second clutch member may be slidable along the second
power transmission members, anti-rotation means may be provided on
the second power transmission member to prevent rotation of the
second clutch member around the second power transmission member.
The anti-rotation means may comprise splines which may extend
axially along the second power transmission member.
[0032] In a third embodiment, the coupling assembly may comprise a
centrifugal fluid clutch. The centrifugal fluid clutch may comprise
a first clutch member mounted on the first power transmission
member and a second clutch member mounted on the second power
transmission member.
[0033] The first clutch member may comprise a first clutch plate.
The second clutch member may comprise a second clutch plate. The
first clutch member may comprise a driven clutch member. The second
clutch member may comprise a driving clutch member.
[0034] The centrifugal clutch may further comprise force applying
means to apply a force to at least one of the first and second
clutch members to move the first and second clutch members relative
to each other away from each other, whereby the second clutch
member is disengaged from the first clutch member.
[0035] The force applying means may comprise a piston arrangement.
The piston arrangement may comprise a fluid receiving part to
receive fluid, such as a hydraulic fluid, to apply a force to move
the first and second clutch members relative to each other away
from each other.
[0036] The fluid receiving pail may comprise a chamber to receive
said fluid.
[0037] The centrifugal clutch may further include engaging means to
move the first and second clutch members relative to each other
into engagement with each other. The engaging means may comprise a
resilient urging member, which may be a spring or an arrangement of
springs. The, or each, spring may be annular.
[0038] The second power transmission member may comprise a radially
extending part which may be annular. The resilient urging member
may engage the aforesaid radially extending part. Preferably, the
resilient urging member is arranged between the radially extending
part and the second clutch member to urge the second clutch member
into engagement with the first clutch member.
[0039] The chamber may be arranged to receive fluid therein.
Preferably, the second power transmission member defines one or
more radially extending apertures through which the fluid can be
supplied from the centre of the second power transmission member
into the chamber. Thus, as the speed of rotation of the second
transmission member increases, the fluid is moved by centrifugal
force into the chamber and acts on the piston to disengage the
second clutch member from the first clutch member.
[0040] A safety member may be provided to engage the piston to
prevent the second clutch plate engaging the first and second power
transmission members, the safety member may be expandable to engage
the piston as aforesaid. The safety member may comprise a ring,
conveniently, a split ring. Thus, in the preferred embodiment, the
safety member holds the first and second clutch members disengaged
from each other in the event that the supply of fluid fails.
[0041] In a fourth embodiment, the coupling assembly may comprise a
gear arrangement, which may comprise a plurality of gear members.
The gear arrangement may comprise a primary sun gear. The primary
sun gear may be mounted on one of the first and second power
transmission members. The gear arrangement may further comprise a
secondary sun gear. The secondary sun gear may be mounted on the
other of the first and second power transmission member.
[0042] Preferably, the primary sun gear is mounted on the second
power transmission member. Preferably, the secondary sun gear is
mounted on the first power transmission member.
[0043] The gear arrangement may comprise at least one primary
planet gear in engagement with the primary sun gear. The sun gear
arrangement may further comprise at least one secondary planet
gear, which may be in engagement with the secondary sun gear.
[0044] The primary planet gear is preferably connected to the
secondary planet gear so that the primary and secondary planet
gears rotate with each other. Advantageously, the primary and
secondary planet gears are connected to each other so that they
rotate synchronously with each other.
[0045] The gear arrangement may comprise a plurality of primary
planet gears and a corresponding plurality of secondary planet
gears. Each primary planet gear is preferably fixedly connected to
a respective one of the secondary planet gears.
[0046] The gear arrangement may further include a carrier which may
be in the form of an annular member. The, or each primary planet
gear may be arranged on one axial side of the carrier and the, or
each, secondary planet gear may be arranged on the opposite axial
side of the carrier.
[0047] Preferably, the primary and secondary planet gears are
connected to one another by a shaft. The, or each, shaft preferably
extending through the carrier, and the, or each, shaft is
preferably rotatable relative to the carrier.
[0048] A brake may be provided to brake the carrier to restrict or
prevent movement of the carrier. When the brake is applied,
rotation of the primary sun gear is transmitted via the primary and
secondary planet gears to the secondary sun gear to effect rotation
of the secondary sun gear, thereby transmitting rotation of one of
the first and second power transmission members to the other of the
first and second power transmission members. When the brake is not
applied and the carrier is free to rotate the primary and secondary
sun gears can rotate independently of each other, thereby allowing
the first and second power transmission members to rotate
independently of each other.
[0049] It will be appreciated by the skilled person that
appropriate selection of gear ratios enables the rotation of the
first and second power transmission members to be coupled to each
other when the carrier is locked and enables the first and second
power transmission members to rotate independently of each other
when the brake is released.
[0050] In another embodiment, the coupling assembly may be arranged
to automatically disconnect the first and second power assemblies
when the drive arrangement is self powering.
[0051] The first power assembly may comprise a first torque
transmitter, and the second power assembly may compromise a second
torque transmitter the coupling assembly may be arranged to
automatically disconnect the first and second torque transmitters
when said torque transmitters rotate at predetermined speeds. The
coupling assembly may be arranged to automatically disconnect the
first and second torque transmitters when the first torque
transmitter means rotates at a greater speed than the second torque
transmitter.
[0052] The coupling assembly may include a ratchet and pawl system,
with pawls on a first shaft selectively engageable with ratchets on
a second concentric shaft. The second shaft may be located within
the first shaft.
[0053] Alternatively the coupling assembly may be of a different
mechanical lock up type such as a sprag or roller ramp arrangement.
Alternatively the coupling assembly may be of a friction type and
perhaps in the form of a drum, disc or cone arrangement.
[0054] The coupling assembly may be of an electromagnetic type, and
may be in the form of a magnetic particle, eddy current or
hysteresis arrangement. As further alternatives the connection
means may comprise an oil sheer arrangement, a friction plate or
electromagnetic clutch, a hydraulic torque converter with bypass
valve or an electric motor.
[0055] The first and second power transmission members may extend
respectively from the first and second torque transmitters with the
coupling assembly engageable between first and second power
transmission members. The first and second power transmission
members may comprise first and second concentric shafts.
[0056] The intermediate pressure and high pressure turbines may
rotate in respective opposite directions, with gearing provided to
cause the first and second power transmission members to rotate in
the same direction. The first and second torque transmission
members may be in the form of concentric shafts.
[0057] The coupling assembly may be arranged such that the first
and second power transmission members and hence the first and
second torque transmitters disconnect when the first power
transmission member rotates at a greater speed than the second
power transmission member.
[0058] The second torque transmitter may be arranged to drive a
power takeoff. The power takeoff may connect to a generator, and
the starter may be arranged to switch to being a generator
following starting of the drive arrangement.
[0059] The coupling assembly may include sensors to detect the
speed of the first and second power transmission members and hence
the speed of the first and second torque transmitters which sensors
may be connected to a control unit to the drive arrangement.
[0060] According to another aspect of the present invention there
is provided a gas turbine engine, the engine including first and
second compressors; first and second turbines; a first drive means
to connect the first compressor to the first turbine such that
during running of the engine the first turbine drives the first
compressor; second drive means to connect the second compressor to
the second turbine such that during running of the engine the
second turbine drives the second compressor; engine starter means
for turning the engine during starting thereof; a power
transmission arrangement as described above connected to the
starter means and arranged to couple together the first and second
drive means during starting, such that both the first and second
drive means are turned by the starter means during starting, the
power transmission arrangement also being arranged to decouple the
first and second drive means following starting to permit
independent turning thereof.
[0061] Preferably, the engine includes power receiving means
connected to the second drive means. Preferably, the second drive
means drives the power receiving means after decoupling of the
first and second drive means from each other.
[0062] The first compressor may comprise a high pressure
compressor. The first turbine may comprise a high pressure turbine.
The first drive means may comprise a high pressure shaft
interconnecting the high pressure compressor and turbine.
[0063] The second compressor may comprise an intermediate pressure
compressor. The second turbine may comprise an intermediate
pressure turbine. The second drive means may comprise an
intermediate shaft interconnecting the intermediate pressure
compressor and turbine.
[0064] According to another aspect of this invention there is
provided a coupling assembly comprising a main body having a first
part coupled by fluid to a second part, the first part being
mountable on a first power transmission member and the second part
being mountable on a second power transmission member, the main
body defining a space to receive at least one of the power
transmission member, and the coupling assembly further comprising
fluid supply means for supplying fluid to the main body to supply
fluid to a region of the main body outside the aforesaid space.
[0065] Preferably, the fluid comprises a hydraulic fluid. The first
part may comprise a first fluid chamber, and the second part may
comprise a second fluid chamber.
[0066] Each of the first and second fluid chambers may be of an
annular configuration. Preferably, each of the first and second
fluid chambers is of a toroidal configuration. Each of the
aforesaid toroids may be defined by a semi-circle. Preferably, the
main body has a configuration of a torus defining said space, which
is preferably a central space of the torus.
[0067] Preferably, the space can receive the second power
transmission member. In one embodiment, the space may receive both
of said power transmission members. The second power transmission
member may extend wholly through the space.
[0068] Each of the fluid chambers preferably includes a plurality
of vanes, which may be radially extending vanes.
[0069] The main body may include drain means to allow fluid in the
main body to drain therefrom. Preferably, the drain means comprises
a drain aperture or a plurality of drain apertures defined in the
main body. The, or each, drain aperture may be defined in a region
between the first and second chambers. The clutch assembly may
include an enclosure in which the main body is arranged.
Preferably, fluid from the main body can drain into the
enclosure.
[0070] Embodiments of the invention will now be described by way of
example only, with reference to the accompanying drawings, in
which:--
[0071] FIG. 1 is a sectional side view of the upper half of a gas
turbine engine;
[0072] FIG. 2 is a diagrammatic more detailed cross sectional view
through part of the engine shown in FIG. 1 showing one embodiment
of a power transmission arrangement;
[0073] FIG. 3 is a cross-sectional view in the direction of the
arrows III-III in FIG. 2;
[0074] FIG. 4 is a cross-sectional view in the direction of the
arrows IV-IV in FIG. 2;
[0075] FIG. 5 is a diagrammatic cross-sectional view through part
of the engine shown in FIG. 1, showing a further embodiment of a
power transmission arrangement;
[0076] FIG. 6 is a diagrammatic cross-sectional view through part
of the engine shown in FIG. 1, showing another embodiment of a
power transmission arrangement;
[0077] FIG. 7 is a diagrammatic cross-sectional view through part
of the engine shown in FIG. 1 showing yet another embodiment of a
power transmission arrangement;
[0078] FIG. 8 is a diagrammatic cross-sectional view through part
of the engine shown in FIG. 1 showing a further embodiment of a
power transmission arrangement;
[0079] FIG. 9 is a view along the arrow A in FIG. 8;
[0080] FIG. 10 is a diagrammatic cross-sectional view through part
of the engine shown in FIG. 1 showing a still further embodiment of
a power transmission arrangement.
[0081] Referring to FIG. 1, a gas turbine engine is generally
indicated at 10 and comprises, in axial flow series, an air intake
11, a propulsive fan 12, an intermediate pressure compressor 13, a
high pressure compressor 14, a combustor 15, a turbine arrangement
comprising a high pressure turbine 16, an intermediate pressure
turbine 17 and a low pressure turbine 18, and an exhaust nozzle
19.
[0082] The gas turbine engine 10 operates in a conventional manner
so that air entering the intake 11 is accelerated by the fan 12
which produce two air flows: a first air flow into the intermediate
pressure compressor 13 and a second air flow which provides
propulsive thrust. The intermediate pressure compressor compresses
the air flow directed into it before delivering that air to the
high pressure compressor 14 where further compression takes
place.
[0083] The compressed air exhausted from the high pressure
compressor 14 is directed into the combustor 15 where it is mixed
with fuel and the mixture combusted. The resultant hot combustion
products then expand through, and thereby drive, the high,
intermediate and low pressure turbines 16, 17 and 18 before being
exhausted through the nozzle 19 to provide additional propulsive
thrust. The high, intermediate and low pressure turbines 16, 17 and
18 respectively drive the high and intermediate pressure
compressors 14 and 13 and the fan 12 by suitable interconnecting
main shafts.
[0084] FIGS. 2 and 3 show a power transmission arrangement 20
arranged between the intermediate and high pressure compressors 13,
14. The location of the power transmission arrangement 20 is
indicated diagrammatically at 22 on FIG. 1. The power transmissions
arrangement 20 is usable when starting the engine 10 and also
providing a power takeoff during running of the engine 10.
[0085] The power transmission arrangement 20 comprises coaxial
first and second power transmission shafts 24, 26, with the second
power transmission shaft 26 arranged within the first power
transmission shaft 24. The first and second power transmission
shafts 24, 26 extend generally to first and second torque
transmitters in the form of the high pressure and intermediate
pressure main shafts 28, 30. The first power transmission shaft 24
extends to a high pressure main shaft 28 interconnecting the high
pressure compressor 14 and the high pressure turbine 16. The first
power transmission shaft 24 is drivingly connected to the high
pressure main shaft 28 by a first bevelled gear arrangement 32. The
second power transmission shaft, 26 connects to the intermediate
pressure main shaft 30 by a second bevelled gear arrangement 34 in
an opposite orientation to the gear 32. The main shafts 28, 30 in
use rotate in opposite directions, but the opposite alignment of
the bevelled gear arrangement 32, 24, causes the first and second
power transmission shafts 24, 26 to rotate in the same direction.
The first and second power transmission shafts 24, 26 are
selectively coupled to, and decoupled from, each other by a
coupling assembly 36.
[0086] The coupling assembly 36 comprises a main body 38 in the
form of a torus defining a central space 40 through which the
second power transmission shaft 26 extends. The second power
transmission shaft 26 is connected via a third gear arrangement 42
to a third power transmission member 44, which is, in turn,
connected to a start-up motor or power takeoff generator 62 (see
FIG. 1).
[0087] The main body 38 of the coupling assembly 36 comprises a
first annular chamber 46 (shown in more detail in FIG. 3) to which
the first power transmission shaft 24 is connected, and a second
annular chamber 48 (shown in more detail in FIG. 4) to which the
second power transmission shaft 26 is connected. A plurality of
radially extending first vanes 49A are provided in the first
annular chamber 46, and a plurality of radially extending second
vanes 49B are provided in the second annular chamber.
[0088] A fluid supply means 50A is provided to supply a fluid
internally of the portion 26A of the second power transmission
shaft 26, the portion 26A being arranged within the central space
40. The fluid supply means supplies fluid to a region internally of
the central space 40 of the main body 38 at the portion 26A via a
fluid inlet aperture 52A in the side wall of the second power
transmission shaft 26. The fluid inlet aperture 52A extends from
the portion 26A to the inside of the main body 38.
[0089] Alternatively, a fluid supply assembly 50B could be provided
to supply fluid externally of the central space and externally of
the portion 26A to a fluid supply aperture 52B in the wall of the
second fluid chamber 48.
[0090] A drain channel 56 is provided to drain fluid from the main
body 38 of the coupling assembly 36. The fluid drains via the drain
channel 56 is fed into an annular enclosure 58. Suitable
circulating means 60 is provided to recirculate the fluid back to
the main part 38 via the fluid supply means 50A or 50B.
[0091] In use, for example when it is desired to start-up an
engine, the third power transmission member is connected to a start
up motor, and the main body 38 of the coupling assembly 36 is at
least partially filled with hydraulic fluid via the fluid supply
means 50A or 50B. When the start up motor is turned on, the third
power transmission member 44 rotates driving the second power
transmission member 26 via the gear arrangement 42. As a result,
the second chamber 48 of the main body 38 of the coupling assembly
36 also rotates. Fluid in the second fluid chamber 48 is moved
outwardly by centrifugal force and as the speed increases. The
hydraulic fluid is flung out of the second fluid chamber 48 into
the first fluid chamber 46. The second vanes 49B assist in causing
the fluid to move into the first fluid chamber 46. As the fluid
passes into the first fluid chamber 46, the fluid strikes the first
vanes 49A, thereby transferring the angular momentum of the fluid
to the first fluid chamber 46. This causes the first fluid chamber
46 to rotate in the same direction as the second fluid chamber 48.
The hydraulic fluid is drained out of the main part body 38 via the
drain apertures 56 to be recirculated via the recirculating means
60 to be supplied back to the main body 38 by the fluid supply
means 50A or 50B.
[0092] Thus, during start up of the engine 10, the first and second
power transmission shafts 24, 26 are coupled together by the action
of the fluid between the first and second members 46, 48 of the
coupling assembly 36 and both of the first and second power
transmission members 24, 26 rotate together. As explained above,
the first power transmission member 24 is drivingly connected to
the high pressure shaft 28 and thereby the rotation of the first
power transmission member 24 turns the high pressure shaft 30,
thereby turning the high pressure compressor 14 and turbine 16. At
the same time, fuel is supplied to the combustor 15 and igniters
are operated to ignite the engine. When ignition has started and
the engine is self powering, the supply of fluid to the main body
38 of the coupling assembly 36 can be shut off. As a result, fluid
draining from the main body 38 is not replenished and eventually
the main body 38 is emptied of fluid and the first fluid chamber 46
is decoupled from the second fluid chamber 48 to allow the first
and second power transmission members 24, 26 and, thereby the high
and intermediate pressure main shafts 28, 30 to turn
independently.
[0093] The operation of the gas turbine engine 10 is required to
provide electricity to various parts of the aeroplane. Power is
taken off from the intermediate pressure main shaft 30 via the
second power transmission shaft 26 which is connected by the gear
34 to the intermediate pressure main shaft 30. The second power
transmission shaft 26 is also connected via the gear arrangement 42
to the third power transmission member 44 which, in turn, can be
connected to a generator for generating electric power. Thus, when
the coupling assembly 36 is in its decoupled condition, decoupling
the first and second power transmission shaft 24, 26, from each
other, power can be taken directly from the intermediate pressure
shaft 30 without involving the high pressure shaft 28.
[0094] Referring to FIG. 5, there is shown a further embodiment of
a power transmission arrangement. In FIG. 5, many of the features
are the same as in FIG. 2 and these have been designated with the
same reference numerals.
[0095] The first and second power transmission shafts 24, 26 are
selectively coupled to, and decoupled from, each other by a
coupling assembly in the form of a friction clutch 70.
[0096] The friction clutch 70 comprises a driven clutch plate 72
fixedly mounted on the first power transmission shaft 24, and a
driving clutch plate 74 slidably mounted on the second power
transmission shaft 26. The driving clutch plate 74 can slide along
the second power transmission shaft 26 in the direction indicated
by the double headed arrow 76 but is prevented from rotating around
the second power transmission shaft 26 by axially extending splines
78 on the second power transmission shaft 26.
[0097] The friction clutch 70 also comprises force applying means
in the form of a piston arrangement 80 and a thrust bearing 82
connected to the driving plate 74 and to the piston arrangement
80.
[0098] The piston arrangement 80 comprises an annular piston holder
84 and a piston 85. The piston holder 84 defines first and second
chambers 86, 88. The piston 85 comprises an annular radially
outwardly extending separator 90 which extends into the piston
holder 84 to separate the first and second chambers 86, 88 from
each other.
[0099] The piston 85 also includes an annular axially extending
piston member 92 to which the separator 90 is fixedly connected.
The piston member 92 is connected to the thrust bearing 82.
[0100] First and second hydraulic fluid supply lines 94, 96 are
provided to supply hydraulic fluid respectively to the first and
second chambers 86, 88 to move the piston 85 in the directions
indicated by the arrows 98, 100. In operation, hydraulic fluid
supplied along the first fluid supply line 94 enters the first
chamber 86 and the force provided by the pressure in the first
chamber 86 pushes the separator 90 and, hence, the piston member
92, and the driving clutch plate 74 in the direction indicated by
the arrow 100, thereby disengaging the driving clutch plate 74 from
the driven clutch plate 72 to decouple the first power transmission
shaft 24 from the second power transmission shaft 26. When
hydraulic fluid is supplied along the second fluid supply line 96,
the fluid enters the second chamber 88 and the pressure therein
pushes the separator 90 and hence the driving clutch plate 74 in
the direction indicated by the arrow 98 to engage the driven clutch
plate 72, thereby coupling the first power transmission shaft 24 to
the second power transmission shaft 26.
[0101] Referring to FIG. 6 there is shown a further embodiment of a
power transmission arrangement, designated 120. In FIG. 6 many of
the features are the same as in FIGS. 2 and 5, and these have been
designated with the same reference numeral.
[0102] The first and second power transmission shafts 24, 26 are
selectively coupled to, and decoupled from, each other by a
coupling assembly in the form of a fluid clutch 170.
[0103] The fluid clutch 170 comprises a driven clutch plate 172
fixedly mounted on the first power transmission shaft 24, and a
driving clutch plate 174 slidably mounted on the second power
transmission shaft 26. The driving clutch plate 174 can slide along
the second power transmission shaft 26 in the direction indicated
by the double headed arrow 176, but is prevented from rotating
around the second power transmission shaft 26 by axially extending
splines 178 on the second power transmission shaft 26.
[0104] The fluid clutch 170 also comprises force applying means in
the form of a spring arrangement 180 and a reaction member in the
form of a reaction plate 182 that extends radially from the second
power transmission shaft 26. The spring arrangement 180, which
surrounds the second power transmission shaft 26, bears against the
reaction plate 182 and the driving clutch plate 174 to push the
driving clutch plate 174 towards the driven clutch plate 172.
[0105] A housing 184 comprises an axially extending annular wall
member 185 which extends around the spring arrangement 180. The
wall member 185 also extends axially along the second power
transmission member 26 beyond the reaction plate 182 to define a
toroidal chamber 186 on the opposite side of the reaction plate 182
to the spring arrangement 180. The portions of the housing 184
defining the chamber 186 provide a portion 187, as explained below.
The housing 184 also includes an inwardly extending member 188
which extends from the wall member 185 towards the second power
transmission shaft 26. Thus, the chamber 186 is defined by the wall
members 185, the reaction plate 182, and the inwardly extending
member 188 and the second power transmission member 26. As can be
seen the annular inwardly extending member 188 is tapered relative
to the reaction plate 182.
[0106] In operation, after the engine has been started up and is
self sustaining the first and second power transmission shafts
rotate at high speeds. Oil is then supplied, as indicated by the
arrow 190 into a longitudinally extending bore 192 in the second
power transmission shaft 26. The second power transmission shaft 26
defines a plurality of radially extending feed holes 194 which
extend through the second power transmission shaft 26 from the bore
192 to feed oil into the chamber 186.
[0107] As the oil enters the chamber 186 under centrifugal force,
the oil is at a high pressure, which pushes axially on the inwardly
extending member 188 to move the piston 187 in the direction of the
arrow 196, thereby separating the driving clutch plate 174 from the
driven clutch plate 172 to allow the first and second power
transmission shafts 24, 26 to rotate independently of each
other.
[0108] The fluid clutch 170 also includes a safety ring 198
provided within the chamber 186 around the second power
transmission member 26. The safety ring 198 is a split ring and
during operation of the engine, the centrifugal force created by
the rotation of the second power transmission shaft 26 cause the
ring 198 to open and move radially outwardly to the position shown
in broken lines in FIG. 6. In this position the ring 198 can
prevent the clutch plates 172, 174 from re-engaging each other if
the supply of oil into the chamber 186 should fail.
[0109] As an alternative to the steps of feeding oil to the chamber
196 only when the engine is self sustaining, the portion 187 can be
configured such that oil is fed to the chamber constantly but the
portion 187 would be moved in the direction of the arrow 196 only
when the second power transmission shaft 26 reaches a predetermined
speed.
[0110] A further embodiment of a power transmission arrangement,
designated 220, is shown in FIG. 7, in which many of the features
are the same as shown in FIGS. 2, 5 and 6. These features have been
designated with the same reference numeral.
[0111] The first and second power transmission shafts 24, 26 are
connected to each other by a planetary gear arrangement 200.
[0112] The planetary gear arrangement 200 comprises a primary sun
gear 202, fixedly mounted on the second power transmission shaft
26, and a secondary sun gear 204, fixedly mounted on the first
power transmission shaft 24. The planetary gear arrangement 200
include a plurality of primary planetary gears 206, each being in
meshing engagement with the primary sun gear 202, and further
includes a plurality of secondary planet gears 208, each being in
meshing engagement with the secondary sun gear 204. The primary and
secondary planet gears 206, 208 are co-axial with one another and
are connected to each other at their axes by a respective gear
shaft 210. The gear shafts 210 transmit rotary motion of the
primary planet gears 206 to the respective secondary planet gears
208.
[0113] An annular carrier 212 is provided between the primary and
secondary planet gears 206, 208, such that the primary and
secondary planetary gears 206, 208 are arranged on opposite axial
sides of the carrier. The main axis of the carrier is coincident
with the main axes of the first and second power transmission
shafts 24, 26. The gear shaft, 210 extend through the carrier 212
and rotation of the carrier 212 about the first and second power
transmission shaft 24, 26 causes corresponding rotation of the
primary and secondary planet gears 206, 208 about the first and
second power transmission shafts 24, 26.
[0114] A brake 214 is provided. The brake 214 has a braking
position in which the brake 214 engages the carrier 212 and locks
the carrier 212 to prevent rotation of the carrier 212. The brake
214 also has a released position in which the carrier 212 is not
locked by the brake 214 and can rotate around the first and second
power transmission shafts 24, 26.
[0115] When the brake 214 is in the braking position, the carrier
212 is prevented from rotating around the first and second power
transmission members 24, 26. As a result the primary and secondary
planet gears 206, 208 are also prevented from rotating around the
first and second power transmission shafts 24, 26. In this
condition, the rotation of the second power transmission shaft 26
is transmitted by the primary sun gear 202 to the primary planet
gear 206 to cause the primary planet gear 206 to rotate about its
own axis. This rotation is transmitted by the gear shaft 210 to the
secondary planet gear 208. The rotation of the secondary planet
gear 208 causes the secondary sun gear 204 to rotate which, in
turn, causes the second power transmission shaft 24 to rotate about
its axis.
[0116] Thus, when the brake 214 is applied and is in the braking
position, in the first and second power transmission shafts are
coupled to each other and rotation of the second power transmission
shaft 26 is transmitted via the planetary gear arrangement 200 to
the first power transmission shaft 24, thereby causing the first
and second power transmission shaft 24, 26 are coupled to each
other.
[0117] When the brake 214 is released, the primary and secondary
planet gears 206, 208, and hence the carrier 212 rotate around the
first and second power transmission shaft 24, 26. This allows the
first and second power transmission shafts effectively, to rotate
independently of one another. Thus, when the brake 214 is released
the first and second power transmission shafts 24, 26 are
effectively decoupled from one another.
[0118] Referring to FIGS. 8 and 9, there is shown a further
embodiment of the power transmission arrangement, designated
320.
[0119] The arrangement 320 shown in FIGS. 8 and 9 comprises
concentric first and second power transmission shafts 324, 326 with
the shaft 324 located within the shaft 326. The power transmission
shafts 324, 326 extend generally radially relative to the
intermediate pressure and high pressure shafts 28, 30 of the gas
turbine engine 10. The first power transmission shaft 324 connects
to the high pressure shaft of the gas turbine engine 10 and the
second power transmission shaft 326 connects to the intermediate
pressure shaft of the gas turbine engine 10.
[0120] The first and second power transmission shafts 324, 326
terminate in a coupling assembly 336, which comprises a plurality
of ratchets 338 around the circumference of the first power
transmission shaft 324. Three pawls 340 are provided on the
interior of the second power transmission shaft 326 and are urged
by springs 342 onto the ratchets 338. Speed sensors 344 are
provided in the coupling assembly 336 to detect the respective
speeds of the first and second power transmission shafts 324, 326
and transmit these to an engine control unit (not shown).
[0121] A gear arrangement 346 is provided towards the end of the
second power transmission shaft 326 to connect the intermediate
pressure power transmission shaft to the third power transmission
shaft 44.
[0122] In use, to start the engine 10, the unit 62 acts as a
starter to rotate the third power transmission shaft 44. This
causes via the gear arrangement 346, the second power transmission
shaft 326 to rotate, and the coupling arrangement 336 also causes
the first power transmission shaft 324 to rotate. These cause the
intermediate pressure compressor 13 and turbine 17 to turn, and
also cause the turning of the high pressure compressor 14 and
turbine 16.
[0123] Once the engine 10 becomes self running the high pressure
shaft 28 and hence the first power transmission shaft 324 will
rotate at a higher speed than the intermediate pressure shaft 30
and second power transmission shaft 326. With reference to FIG. 9
this causes the ratchets 338 to move past the pawls 140 in the
anticlockwise direction shown by the arrows 354 to allow different
relative speeds. Once the engine 10 is self running, the unit 62
will switch from being a starter to a generator, and the generator
will be powered by the second transmission shaft 326 via the gear
arrangement 346 and the third transmission shaft 44.
[0124] The increased drag on the intermediate pressure compressor
13 increases the gradient of this compressor's working line, and
therefore improves handling characteristics. This enables the
intermediate pressure compressor 13 to be designed with reduced
surge margin at design point and thus be able to achieve higher
work per stage and improved efficiency.
[0125] In use, the high pressure shaft 30 rotates at approximately
three times the speed of the intermediate pressure shaft 28. It is
advantageous that power is taken off the intermediate pressure
shaft 28 as mechanical drag is less than for the high pressure
shaft 30.
[0126] These arrangements 20, 120, 220 and 320 also enable the high
pressure shaft 28 to be turned during the starting, but not of
course to generate auxiliary power. It is advantageous to start
turning the high pressure shaft 28 as it has lower inertia, and the
high pressure compressor 14 delivers a set pressure charge to the
combustion chamber 15 supplying sufficient power to push the burnt
gases rearward through the high pressure turbine 16, thereby giving
self powering. If only the intermediate pressure shaft 30 is turned
during starting, air has to be compressed and pushed through the
high pressure turbine 16 before self power takes over. This leads
to a relatively slow starting.
[0127] The speed sensors can be used in conjunction with the engine
control unit to avoid crash re-engagement of the coupling
arrangements 336. This could occur when the high pressure shaft 28
is rotating at the same time as the unit 62 is operating as a
starter. With input from the speed sensors 344 the unit 62 can be
controlled to re-engage smoothly with the first power transmission
member 324.
[0128] A further embodiment is shown in FIG. 10, which is similar
to the embodiment shown in FIG. 2 and the same features have been
designated with the same reference numerals.
[0129] The embodiment shown in FIG. 10 differs from that shown in
FIG. 2 in that the coupling assembly 36 is offset from the first
and second power transmission shafts 24, 26. Also, the third power
transmission shaft 44 is connected directly to the second annular
chamber 48, and is co-axial therewith.
[0130] The third power transmission shaft 44 is connected by the
gear arrangement 42 to the second power transmission shaft 26 and,
as such, is the same as the embodiment shown in FIG. 2. However,
the first power transmission shaft 24 is connected to the first
annular chamber 46 by a first ancillary gear arrangement 443, and
an ancillary shaft 445. The subsidiary shaft 445 is mounted
directly on the first annular chamber 46.
[0131] This arrangement has the advantage that the gear
arrangements 42, 443 allow the speed ratio between the first and
second power transmission shafts (and therefore between the main
shafts during engine starting) to be tailored more efficiently for
optimum engine performance.
[0132] There are thus described efficient arrangements for
providing start up power in the gas turbine engine to the high
pressure shaft and for taking power from the gas turbine engine via
the intermediate pressure shaft and allowing two shafts to be
coupled to each other and decoupled from each other as desired.
[0133] Various modifications can be made without departing from the
scope of the invention. For example in the case of the friction
clutch shown in FIG. 5, an engagement spring 97 (shown in broken
lines in FIG. 5) can be provided on one side of the separator 90 to
assist engagement of the clutch plates 72, 74 at low speeds.
Similarly, a second disengagement spring 99 can be provided on the
other side of the separator 90 to ensure disengagement of the
clutch plates 72, 74 in failure conditions.
[0134] Whilst endeavoring in the foregoing specification to draw
attention to those features of the invention believed to be of
particular importance it should be understood that the Applicant
claims protection in respect of any patentable feature or
combination of features hereinbefore referred to and/or shown in
the drawings whether or not particular emphasis has been placed
thereon.
* * * * *