Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A THRUST PRODUCING UNIT WITH A FAIL-SAFE ELECTRICAL
DRIVE UNIT
The present embodiments relate to a thrust producing unit, and,
more particularly, to a thrust producing unit with a fail-safe electrical
drive unit that drives a rotor of a rotary-wing aircraft.
Safety is absolutely paramount in air transportation. In fact, air
transportation is a field that must typically take into account strict
applicable authority regulations, certification requirements, and safety
demands independent of a selected air transportation vehicle, such as
e. g. helicopters, airplanes, hybrid aircrafts, rockets and so on. Such
authority regulations, certification requirements, and safety demands
are e.g. specified by the US-American Federal Aviation Regulations
(FAR) from the US-American Federal Aviation Administration (FAA),
the European Certification Specifications (CS) from the European
Aviation Safety Agency (EASA) and/or other aviation authority ruling.
Fixed-wing aircrafts and rotary-wing aircrafts address these
safety regulations in several different ways. The most common
approach for fixed-wing aircrafts involves the use of overpowered jet
engines so that the fixed-wing aircraft continues to be operational with
the remaining operative jet engines when one jet engine fails.
In contrast thereto, most rotary-wing aircrafts rely on the auto-
rotation capability that most rotors provide and the use of two or more
engines that are connected to a same rotor, whereby the rotor remains
operational when one of the engines fails.
Recently, urban air mobility (UAM) is emerging as a new market
with new safety challenges. In particular, most current solutions for
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urban air mobility (UAM) involve vertical take-off and landing (VTOL)
aircrafts with one or more thrust producing units that have an
electrical drive and are usually equipped with fixed pitch propellers
which do not have the auto-rotation capability of other rotary-wing
aircrafts. Thus, the aviation manufacturers that produce VTOL aircrafts
for the UAM market have to imagine new solutions to provide an extra
layer of safety.
Document WO 2018/77773 Al relates to a particularly redundant
electrical machine for driving a means of propulsion with increased
reliability. The machine comprises a plurality of independent partial
rotors which are respectively coupled to a common shaft by means of
freewheel devices in order to drive said shaft and the means of
propulsion therewith in a working direction of rotation. The machine
also comprises a plurality of independent stator winding systems, a
stator winding system and a partial rotor being respectively associated
with each other and arranged in such a way that they can
electromagnetically interact with each other. The stator winding
systems are successively arranged in the axial direction. Similarly, the
partial rotors are successively arranged in the axial direction.
However, the redundant electrical machine involves a geared
solution with two or more motors. The geared solution is very heavy,
not flexible in view of revolutions-per-minute (RPM), and not lightning
strike safe. Furthermore, the geared solution is not flexible in view of
an RPM adaption. Moreover, because of the geared solution, oil
lubrication and a chip detector are needed, and one mechanical error
can damage the whole gearbox.
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Document DE 10 2016 220 234 Al relates to a release coupling
device for troubleshooting an electrical machine, comprising a
coupling element for coupling at least two rotors having a shaft via a
connection and a decoupling element for decoupling at least one rotor
of the two rotors of the shaft by separating the compound, if an error
occurs, wherein the at least one rotor of the two rotors is associated
with the error.
However, the release coupling device involves a clutch with
hirth-teething that separates the at least two rotors in case one motor
fails. Therefore, the release coupling device requires the use of a
separate release element.
Document US 2017/0217600 Al describes a propulsion system
assembly including a driveshaft and a plurality of electric motor
modules. The driveshaft is rotatably mounted to a casing about a drive
axis, the driveshaft including a first shaft end and an opposite facing
second shaft end. The plurality of electric motor modules is in axially
stacked relationship with one another with respect to the drive axis to
define an electric motor module stack, each electric motor module
being configured for transmitting a torque to the driveshaft when
coupled thereto independently of at least one other electric motor
module. Each electric motor module includes a controllable clutch
arrangement for selectively coupling and decoupling the respective
electric motor module with respect to the driveshaft to respectively
enable and disable transmission of torque between the respective
electric motor module and the driveshaft.
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However, the propulsion system assembly involves having a
clutch arrangement that decouples the rotor assembly from the
driveshaft when electrical current to the clutch arrangement is
stopped, leading to a very heavy and complicated system.
Moreover, all these solutions have in common that the propellers
are directly mounted on the motor shaft of the respective electric
motors. Such an electrical propulsion system in which the propellers
are directly mounted on the motor shaft of the respective electric
motors is sometimes also referred to as a direct drive system. As a
result, the direct drive system has to handle all static and dynamic
loads from the propellers, which bears a high risk of a total loss of the
drive unit. Furthermore, direct drive systems are usually not lightning
strike safe.
Document WO 2012/023066 Al describes a propulsion and
motion-transmission assembly, in particular for a rotary-wing aircraft,
the assembly comprising : a first motor-reducer assembly; and a
second motor-reducer assembly, wherein the first and second motor-
reducer assemblies are arranged for driving in rotation at least one
rotor of a rotary-wing aircraft; and wherein each of said first and
second motor- reducer assemblies comprises: - a mechanical
differential including a first input shaft, a second input shaft and an
output shaft; and - a first electric motor and a second electric motor
connected, respectively, to said first and second input shafts, the
output shaft of each motor-reducer assembly being arranged for
connection in rotation to a rotor of a rotary-wing aircraft.
However, the described propulsion and motion-transmission
assembly has a gear transmission installed between the two motors.
Similar to the geared solution of Document WO 2018/77773 Al, the
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described propulsion and motion-transmission assembly is very heavy,
not flexible in view of revolutions-per-minute (RPM), and not lightning
strike safe. Moreover, because of the geared solution, oil lubrication
and a chip detector are needed, and one mechanical error can damage
the whole gearbox.
In summary, many state-of-the-art electrical drive units involve a
direct drive system or a belt drive system combined with a gear
transmission or a clutch arrangement. The direct drive system is not
lightning strike safe and the motors have to handle all dynamic and
static loads. The belt drive system often requires a gear transmission,
which is very heavy, not flexible in RPM, not lightning strike safe, and
requires oil lubrication and a chip detector.
It is, therefore, an objective to provide a new thrust producing
unit that is suitable to overcome the above-described drawbacks.
The new thrust producing unit should further provide a high
safety level, for example with a redundant motor solution for the
propeller such that a loss of one motor is not catastrophic (i.e., the
loss of one motor should not impact the propeller drive), a lower
voltage level than existing solutions, and lightning strike safety.
Moreover, the new thrust producing unit should be light weight,
minimize noise emission and service requirements, provide for easy
and flexible mounting, flexible power adaption, flexible RPM adaption,
and flexible motor configuration.
The objective is solved by a thrust producing unit. More
specifically, a thrust producing unit may comprise a rotor and a fail-
safe electrical drive unit. The fail-safe electrical drive unit may
comprise first and second input shafts, first and second fixedly
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attached belt pulleys that are fixedly attached to the respective first
and second input shafts, an output shaft that is coupled to the rotor,
first and second freewheeling belt pulleys, first and second belts, and
first and second electric motors.
The first freewheeling belt pulley is mounted to the output shaft
by means of a first freewheel such that the output shaft rotates freely
when the output shaft rotates faster than the first freewheeling belt
pulley. The second freewheeling belt pulley is mounted to the output
shaft by means of a second freewheel such that the output shaft
rotates freely when the output shaft rotates faster than the second
freewheeling belt pulley.
The first belt connects the first fixedly attached belt pulley with
the first freewheeling belt pulley, and the second belt connects the
second fixedly attached belt pulley with the second freewheeling belt
pulley. The first and second electric motors are coupled with the
respective first and second input shafts, wherein the first electric
motor drives the output shaft via the first input shaft, the first fixedly
attached belt pulley, the first belt, and the first freewheeling belt
pulley, and the second electric motor drives the output shaft via the
second input shaft, the second fixedly attached belt pulley, the second
belt, and the second freewheeling belt pulley.
Thus, a freewheel respectively a freewheeling belt pulley is
provided on the output shaft for each of the first and second electric
motors that transmits its torque to the output shaft. Thereby, the
output shaft is not blocked or braked down in case the first or the
second motor fails.
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Instead of connecting the first and second electric motors
directly to the output shaft, the first and second electric motors are
connected to the output shaft for transmission of force by means of a
respective first and second belt to the freewheeling belt pulley of the
output shaft in order to overcome the above-mentioned problems.
In fact, the illustrative thrust producing unit does not require
motor lubrication. In addition, no gearbox and thus, no oil pump is
needed. In case a gearbox is used, the oil has to be pumped through
the gearbox in order to pump the oil to the gears, often against the
gravity force caused by flight manoeuvres of the aircraft. Omitting
gearbox and oil pump leads to weight savings and minimizes service
requirements.
Generally free wheeled bearings are not very suitable for high
RPM because the centrifugal force produces a force which causes a
lifting movement of the spring-loaded clamping bodies. In such an
event, the friction between the clamping bodies and the housing
surface of the bearing decreases, which causes slippage and thereby
heat production. Therefore, low RPM is provided for free bearings,
respectively freewheeling belt pulleys.
Chip detection enables the early detection of material breakouts
in the transmission respectively in gearboxes. Neither material
eruptions nor a wear pattern occurs by using the illustrative thrust
producing unit. Thus, chip detection can be omitted leading to a
decrease in cost.
Usually, the electrical phenomena and partial discharge effect at
high electrical operating voltages becomes more effective and
therefore more dangerous with increasing flight altitude. Because two
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or more separate electric motors are used, the voltage level of the fail-
safe electrical drive unit can be reduced significantly to the non-
critical range.
Illustratively, the thrust producing unit has no gearbox, no liquid
engine cooling, and no additional inverters with liquid cooling leading
to significant weight savings compared to conventional drive systems
with comparable operational reliability.
By way of example, the rotational speed of the rotor can be
adapted by simply replacing the pulleys with pulleys that have a
different diameter. In conventional thrust producing units with a
gearbox, new gears and possibly new housings may be needed.
Moreover, compared to conventional thrust producing units with
gearboxes, no elaborate production of parts is required for the belt
drive. Some parts can be even produced using a 3D printer.
Illustratively, the belts dampen noises and vibrations in the drive
train compared to conventional thrust producing units. If desired, the
belts may be selected to have high electrical resistance, so that a
static charge of the rotor may be discharged through the belts, while a
lightning strike may be discharged through the belts' housings due to
the higher electrical resistance of the belts. Thus, the risk of a motor
loss caused by lightning strike is reduced drastically.
Furthermore, due to the design, all parts of the belt drive can be
exchanged in a short time. The belts do not require service, and they
can be easily replaced after they have reached their maximal
operating time. In addition, ball bearings and freewheels also have a
fixed service life.
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According to one aspect, the fail-safe electrical drive unit, further
comprises one or more additional input shafts, one or more additional
fixedly attached belt pulleys, one or more additional freewheeling belt
pulleys, one or more additional freewheels, one or more additional
belts, and one or more additional electric motors, wherein each
additional electric motor of the one or more additional electric motors
is coupled with an associated input shaft of the one or more additional
input shafts and drives the output shaft via the associated input shaft,
an associated fixedly attached belt pulley of the one or more additional
fixedly attached belt pulleys, an associated belt of the one or more
additional belts, an associated freewheeling belt pulley of the one or
more additional freewheeling belt pulleys, and an associated freewheel
of the one or more additional freewheels, wherein the associated
fixedly attached belt pulley is fixedly attached to the associated input
shaft, wherein the associated freewheeling belt pulley is mounted to
the output shaft by means of the associated freewheel such that the
output shaft rotates freely when the output shaft rotates faster than
the associated freewheeling belt pulley, and wherein the associated
belt connects the associated fixedly attached belt pulley with the
associated freewheeling belt pulley.
According to one aspect, the first input shaft has a first end and
a second end that is opposite the first end, and the fail-safe electrical
drive unit further comprises at least first and second tensioners,
wherein the first tensioner is attached to the first end of the first input
shaft and the second tensioner to the second end of the first input
shaft, wherein the first and second tensioners are adapted to adjust a
tension of the first belt.
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According to one aspect, the fail-safe electrical drive unit further
comprises a bearing support plate that receives at least the first
electric motor and one end of the output shaft.
According to one aspect, the fail-safe electrical drive unit further
comprises an additional bearing support plate that receives at least
one other end of the output shaft.
According to one aspect, the fail-safe electrical drive unit further
comprises ribs that connect the bearing support plate with the
additional bearing support plate for transferring torque generated at
least by the first electric motor from the bearing support plate to the
additional bearing support plate.
According to one aspect, the additional bearing support plate
comprises at least two threaded holes that are located at different
distances from the output shaft.
According to one aspect, at least the first belt is a toothed belt.
According to one aspect, the first and second electric motors are
arranged at a same distance from the output shaft.
According to one aspect, the first electric motor is arranged at a
first distance from the output shaft and the second electric motor is
arranged at a second distance from the output shaft that is different
than the first distance.
According to one aspect, the second distance is at least two
times greater than the first distance.
According to one aspect, the first input shaft, the second input
shaft, and the output shaft are arranged parallel to each other.
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According to one aspect, the thrust producing unit may further
comprise a rotor hub that is coupled between the rotor blades and the
output shaft.
Furthermore, a rotary-wing aircraft may include the thrust
producing unit described above.
According to one aspect, the rotary-wing may include at least
one additional thrust producing unit described above.
Embodiments are outlined by way of example in the following
description with reference to the attached drawings. In these attached
drawings, identical or identically functioning components and elements
are labelled with identical reference numbers and characters and are,
consequently, only described once in the following description.
- Figure 1 is a diagram of a side view of an illustrative rotary-
wing aircraft with exemplary thrust producing units in accordance with
some embodiments,
- Figure 2 is a diagram of an exploded view of an illustrative
thrust producing unit in accordance with some embodiments,
- Figure 3 is a diagram of a compact view of an illustrative thrust
producing unit in accordance with some embodiments,
- Figure 4A is a diagram of an illustrative thrust producing unit
having at least two electric motors arranged at an equal distance from
the output shaft in accordance with some embodiments, and
- Figure 4B is a diagram of an illustrative thrust producing unit
with three aligned electric motors in accordance with some
embodiments.
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Figure 1 shows an aircraft that is embodied by a rotary-wing
aircraft 100. It should be noted that rotary-wing aircraft 100 may be
any aircraft with rotors. Exemplary embodiments of rotary-wing aircraft
100 may include airplanes, vertical take-off and landing (VTOL)
aircrafts, multicopters, helicopters, drones, etc.
Rotary-wing aircraft 100 may have an aircraft airframe 102. The
aircraft airframe 102 defines a supporting structure of aircraft 100 that
is also referred to hereinafter as the fuselage 102 of the rotary-wing
aircraft 100.
The aircraft airframe 102 may be provided with an outer shell
113 that defines an internal volume 102a. According to one aspect, the
internal volume 102a is at least adapted for transportation of
passengers, so that the rotary-wing aircraft 100 as a whole is adapted
for transportation of passengers. The internal volume 102a may be
adapted for accommodating operational and electrical equipment, such
as e.g. an energy storage system that is required for operation of the
rotary-wing aircraft 100.
It should be noted that exemplary configurations of the internal
volume 102a that are suitable for transportation of passengers, but
also for accommodation of operational and electrical equipment, are
readily available to the person skilled in the art and generally
implemented to comply with applicable authority regulations and
certification requirements regarding passenger transportation. Thus,
these configurations of the internal volume 102a are not described in
detail for brevity and conciseness.
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According to one aspect, the rotary-wing aircraft 100 comprises
a predetermined number of thrust producing units 103. If desired, the
predetermined number of thrust producing units 103 comprises at least
two thrust producing units 103a, 103b. If desired, the predetermined
number of thrust producing units 103 may be more than two. For
example, rotary-wing aircraft may comprise three, four, or more thrust
producing units.
It should be noted that the thrust producing units 103a, 103b are
all exemplarily arranged laterally with respect to the fuselage 102. In
other words, thrust producing units of the predetermined number of
thrust producing units 103 are exemplarily arranged on the left or right
side of the fuselage 102 seen in its longitudinal direction. Accordingly,
in Figure 1 only the thrust producing units 103a, 103b are visible,
while other thrust producing units of the predetermined number of
thrust producing units 103 may be masked by fuselage 102.
However, according to one aspect, two additional thrust
producing units may be embodied in an axially symmetrical manner
with respect to the thrust producing units 103a, 103b, wherein a
longitudinal center axis in the longitudinal direction of fuselage 102
defines the symmetry axis. Accordingly, only the thrust producing units
103a, 103b and their constituent elements are described in more detail
hereinafter, while a more detailed description of the additional thrust
producing units is omitted for brevity and conciseness.
It should be noted that this exemplary arrangement is only
described by way of example and not for limiting the present invention
thereto. Instead, other arrangements are also possible and likewise
contemplated. For instance, one or more of the predetermined number
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of thrust producing units 103 may respectively be arranged at a front
and/or rear section of the fuselage 102, and so on.
The thrust producing units 103a, 103b are embodied for
producing thrust in a predetermined direction in operation such that
the rotary-wing aircraft 100 is able to hover in the air as well as to fly
in any forward or rearward direction.
Illustratively, the thrust producing units 103a, 103b are
structurally connected to a predetermined number of structural
supports, which may include at least two structural support members.
Illustratively, the predetermined number of structural supports and the
predetermined number of thrust producing units 103 form a thrust
producing units arrangement.
By way of example, one or more of the thrust producing units
103a, 103b may comprise an associated shrouding in order to improve
underlying aerodynamics and to increase operational safety. By way of
example, a plurality of shrouding units 106 is shown with two separate
shroudings 106a, 106b. Illustratively, the shrouding 106a is associated
with the thrust producing unit 103a, and the shrouding 106b with the
thrust producing unit 103b.
The shroudings 106a, 106b can be made of a simple sheet metal
and/or have a complex geometry. If desired, the shroudings 106a,
106b are connected to the predetermined number of structural
supports 104. More specifically, the shrouding 106a is preferably
connected to the structural support member 104a, and the shrouding
106b to the structural support member 104b.
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According to one aspect, at least one and, preferably, each one
of the thrust producing units 103a, 103b is equipped with at least one
rotor assembly. By way of example, the thrust producing unit 103a is
equipped with a rotor assembly 108a, and the thrust producing unit
103b is equipped with a rotor assembly 108b. The rotor assemblies
108a, 108b illustratively define a plurality of rotor assemblies 108,
which is preferably mounted to the plurality of shroudings 106.
The plurality of rotor assemblies 108 may be powered by an
associated plurality of engines 105a, 105b, which may be embodied as
electrical engines. Illustratively, rotor assembly 108a may be powered
by electrical engine 105a and rotor assembly 108b may be powered by
electrical engine 105b. However, it should be noted that the engines
can respectively be implemented by any suitable engine that is
capable of producing torque in operation, such as a turbine, diesel
engine, Otto-motor, electrical engine and so on. According to one
aspect, fail-safe electrical drive unit 220 of Figure 2 implements at
least one of electrical engines 105a, 105b.
If desired, at least one of the rotor assemblies 108 is
accommodated inside of a respectively associated shrouding of the
plurality of shroudings 106. Illustratively, the rotor assembly 108a,
108b are accommodated inside of shroudings 106a, 106b,
respectively.
In operation of the multirotor aircraft 100, control of thrust
generation by means of the thrust producing units 103a, 103b for
generating thrust in a predetermined direction may either be achieved
by means of an optional pitch variation, by means of RPM variation, or
by means of a combination of pitch and RPM variation. If the rotor
assemblies 108a, 108b of the plurality of rotor assemblies 108 are not
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provided with an optional pitch variation, e.g. if respective rotor blades
of the rotor assemblies 108a, 108b are implemented as fixed pitch
blades, control of the thrust generation by means of pitch variation
cannot by performed. In this case, only RPM variation can be used for
control of the thrust generation.
According to one aspect, a flexible suspension unit is provided.
The flexible suspension unit may be rigidly mounted to the aircraft
airframe 102 and mechanically couple the thrust producing units
arrangement to the aircraft airframe 102 such that the thrust producing
units 103a, 103b are inclinable in relation to the aircraft airframe 102.
Inclinations in a predetermined range between approximately +/- 300
should at least be enabled.
The flexible suspension may have a neutral interface. The
neutral interface may enable the mounting of the thrust producing unit
103a, 103b via the suspension unit to different structures of aircraft
airframe 102. If desired, suitable adapters may be used. It should,
however, be noted that the thrust producing unit maintains the
capability of being inclined relative to aircraft airframe 102.
It should be noted that the term "flexible" refers to the inclination
ability of the thrust producing units 103a, 103b in relation to the
aircraft airframe 102 and to the ability to mount the same thrust
producing unit 103a, 103b to different structures of the aircraft 100
thanks to the neutral interface and the use of suitable adapters.
However, the term "flexible" does not refer to the suspension unit as
such.
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Illustratively, the flexible suspension unit is connected to the
structural support members 104a, 104b for mechanically coupling the
thrust producing units arrangement to the aircraft airframe 102.
Figure 2 is a diagram of an exploded view of an illustrative thrust
producing unit (e.g., thrust producing unit 103a or thrust producing
unit 103b of Figure 1) in accordance with some embodiments.
Illustratively, thrust producing unit 200 may include rotor 210 and
fail-safe electrical drive unit 220. Rotor 210 may include rotor hub 212,
rotor head 213, at least two rotor blades 215a, 215b, and rotor support
214. If desired, rotor support 214 may be part of fail-safe electrical
drive unit 220.
As shown, rotor 210 includes at least two rotor blades 215a,
215b. If desired, the number of rotor blades may be more than two.
For example, rotor 210 may comprise three, four, or more rotor blades.
Illustratively, rotor 210 may include one rotor assembly, whereby
each rotor assembly may include a rotor hub, a rotor head, and at
least two rotor blades. However, rotor 210 may include more than one
rotor assembly, if desired. As an example, rotor 210 may include two
rotor assemblies that define a pair of upper and lower rotor
assemblies. As another example, rotor 210 may include three or four
rotor assemblies.
As shown, fail-safe electrical drive unit 220 may include output
shaft 230, input shafts 240, 243, 246, fixedly attached belt pulleys
250, 253, 256, freewheeling belt pulleys 260, 263, 266, freewheels
261, 264, 267, belts 270, 273, 276, tensioners 271, 272, 274, 275,
277, 278, electric motors 280, 283, 286, bearing support plates 290,
295, and ribs 298.
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Illustratively, output shaft 230 may be coupled to rotor 210. For
example, output shaft 230 may be coupled to rotor 210 via bearing
support plate 295 and rotor support 214. In other words, output shaft
230 may be coupled to rotor blades 215a, 215b via bearing support
plate 295, rotor support 214, rotor hub 212, and rotor head 213.
Fixedly attached belt pulleys 250, 253, 256 may be fixedly
attached to the respective input shafts 240, 243, 246. In other words,
fixedly attached belt pulleys 250, 253, 256 may rotate with and at the
same revolutions per minute (RPM) as the respective input shafts 240,
243, 246 to which they are attached.
Freewheeling belt pulleys 260, 263, 266 may be mounted to the
output shaft 230 by means of freewheels 261, 264, 267 such that the
output shaft 230 rotates freely when the output shaft 230 rotates faster
than a respective freewheeling belt pulley of freewheeling belt pulleys
260, 263, 266.
In other words, a freewheel, which are sometimes also referred
to as an overrunning clutch, of freewheels 261, 264, 267, disengages
from output shaft 230 when output shaft 230 rotates faster than the
freewheel.
Belts 270, 273, 276 may connect the respective fixedly attached
belt pulleys 250, 253, 256 with the respective freewheeling belt pulleys
260, 263, 266.
Belts 270, 273, 276 may be any belt that is adapted for
transmitting power from the respective fixedly attached belt pulleys
250, 253, 256 to the corresponding respective freewheeling belt
pulleys 260, 263, 266. For example, belts 270, 273, 276 may be flat
belts, rope drives, round belts, spring belts, V belts, multi-groove
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belts, ribbed belts, film belts, toothed belts, or any other specialty
belts. In some embodiments, at least one belt of belts 270, 273, 276 is
a toothed belt, which is sometimes also referred to as a timing belt,
notch belt, cog belt, or synchronous belt.
As shown, input shafts 240, 243, 246 and output shaft 230 are
arranged parallel to each other. However, input shafts 240, 243, 246
and output shaft 230 may be arranged non-parallel to each other.
Arranging input shafts 240, 243, 246 and output shaft 230 parallel or
non-parallel to each other may be based on respective belts 270, 273,
276 and/or respective fixedly attached belt pulleys 250, 253, 256
and/or respective freewheeling belt pulleys 260, 263, 266.
Electric motors 280, 283, 286 may be coupled with the respective
input shafts 240, 243, 246 and drive output shaft 230 via the
respective input shaft 240, 243, 246, the respective fixedly attached
belt pulley 250, 253, 256, the respective belt 270, 273, 276, and the
respective freewheeling belt pulley 260, 263, 266.
Electric motors 280, 283, 286 may be any type of electric motor
that is adapted for driving rotor 210 via output shaft 230. Illustratively,
electric motors 280, 283, 286 may be AC type motors or DC type
motors, brushed or brushless, single-phase, two-phase, or three-
phase, air-cooled or liquid cooled, or any combination thereof.
Illustratively, each input shaft of input shafts 240, 243, 246 may
have two ends that are located opposite of each other. As an example,
input shaft 240 may have end 241 and end 242 that is opposite end
241. As another example, input shaft 243 may have end 244 and end
245 that is opposite end 244. As yet another example, input shaft 246
may have end 247 and end 248 that is opposite end 247.
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If desired, at least two tensioners 271 and 272, 274 and 275, or
277 and 278 may be associated with a respective input shaft 240, 243,
246. For example, tensioner 271, 274, 277 may be attached to the
respective end 241, 244, 247 of the respective input shaft 240, 243,
246 and tensioner 272, 275, 278 to the respective end 242, 245, 248
of the respective input shaft 240, 243, 246. Thereby, tensioners 271
and 272, 274 and 275, or 277 and 278 may be adapted to adjust a
tension of the respective belt 270, 273, 276.
Illustratively, fail-safe electrical drive unit 220 may include
bearing support plate 290. Bearing support plate 290 may receive at
least one of electric motors 280, 283, 286 and one end 231 of output
shaft 230.
If desired, fail-safe electrical drive unit 220 may include an
additional bearing support plate 295. Additional bearing support plate
295 may receive at least one other end 232 of output shaft 230.
By way of example, ribs 298 may connect bearing support plate
290 with additional bearing support plate 295. Ribs 298 may be
adapted for transferring torque generated by the at least one of
electric motors 280, 283, 286 from bearing support plate 290 to
additional bearing support plate 295.
A respective electric motor with a respective input shaft, a
respective fixedly attached belt pulley, a respective freewheeling belt
pulley, and a respective freewheel may form an electrical drive
element. As shown in Figure 2, fail-safe electrical drive unit 220 may
include three electrical drive elements.
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The three electrical drive elements may all drive output shaft 230
at a same predetermined speed, if desired. Consider the scenario in
which the electrical drive element associated with electric motor 280 of
the three electrical drive elements fails. For example, electric motor
.. 280 may fail, input shaft 240 or fixedly attached belt pulley 260 may
break, or belt 270 may tear or become loose.
In this scenario, electric motor 280 may fail to drive freewheeling
belt pulley 260 at the same predetermined speed as electric motors
283 or 286 drive respective freewheeling belt pulley 263 or 266. Thus,
freewheeling belt pulley 260 may disengage from output shaft 230,
which may continue to operate at the same predetermined speed
thanks to the two still operational electrical drive elements associated
with electric motors 283 and 286.
If desired, fail-safe electrical drive unit 220 may include only two
electric drive elements. For example, fail-safe electrical drive unit 220
may include first and second input shafts 240, 246, first and second
fixedly attached belt pulleys 250, 256 that are fixedly attached to the
respective first and second input shafts 240, 246, and an output shaft
230 that is coupled to the rotor 210, first and second freewheeling belt
pulleys 260, 266, wherein the first freewheeling belt pulley 260 is
mounted to the output shaft 230 by means of a first freewheel 261
such that the output shaft 230 rotates freely when the output shaft 230
rotates faster than the first freewheeling belt pulley 260, and wherein
the second freewheeling belt pulley 266 is mounted to the output shaft
230 by means of a second freewheel 267 such that the output shaft
230 rotates freely when the output shaft 230 rotates faster than the
second freewheeling belt pulley 266.
Date Re9ue/Date Received 2020-10-16
22
If desired, fail-safe electrical drive unit 220 may further include
first and second belts 270, 276, wherein the first belt 270 connects the
first fixedly attached belt pulley 250 with the first freewheeling belt
pulley 260, and wherein the second belt 276 connects the second
fixedly attached belt pulley 256 with the second freewheeling belt
pulley 266, and first and second electric motors 280, 286 that are
coupled with the respective first and second input shafts 240, 246,
wherein the first electric motor 280 drives the output shaft 230 via the
first input shaft 240, the first fixedly attached belt pulley 250, the first
belt 270, and the first freewheeling belt pulley 260, and wherein the
second electric motor 286 drives the output shaft 230 via the second
input shaft 246, the second fixedly attached belt pulley 256, the
second belt 276, and the second freewheeling belt pulley 266.
If desired, fail-safe electrical drive unit 220 may include more
than two or three electric drive elements. For example, fail-safe
electrical drive unit 220 may include one or more additional input
shafts, one or more additional fixedly attached belt pulleys, one or
more additional freewheeling belt pulleys, one or more additional
freewheels, one or more additional belts, and one or more additional
electric motors, wherein each additional electric motor of the one or
more additional electric motors is coupled with an associated input
shaft of the one or more additional input shafts and drives the output
shaft via the associated input shaft, an associated fixedly attached
belt pulley of the one or more additional fixedly attached belt pulleys,
an associated belt of the one or more additional belts, an associated
freewheeling belt pulley of the one or more additional freewheeling
belt pulleys, and an associated freewheel of the one or more
additional freewheels.
Date Re9ue/Date Received 2020-10-16
23
Illustratively, the associated fixedly attached belt pulley is fixedly
attached to the associated input shaft, wherein the associated
freewheeling belt pulley is mounted to the output shaft by means of
the associated freewheel such that the output shaft rotates freely
when the output shaft rotates faster than the associated freewheeling
belt pulley, and wherein the associated belt connects the associated
fixedly attached belt pulley with the associated freewheeling belt
pulley.
Figure 3 is a diagram of a compact view of illustrative thrust
producing unit 200. As shown, electric motors 280, 283, and 286 are
arranged in motor housings for torque compensation. If desired, the
motor housings of respective electric motors 280, 283, 286 may be
fixedly mounted to bearing support plate 290. The motor driveshaft of
electric motors 280, 283, 286 is attached to the respective input shaft
240, 243, 246.
In order to guarantee the best load transmission from fixedly
attached belt pulleys 250, 253, 256 to the respective freewheeling belt
pulleys 260, 263, 266, each respective belt 270, 273, 276 may be
tightened or loosened by means of the respective belt tensioners 271
and 272, 274 and 275, 277 and 278. Figure 3 shows detailed views of
illustrative tensioners 271, 272 and bearing support plate 295.
Bearing support plate 295 may include hole 330 for receiving one
end of the output shaft (e.g., end 232 of output shaft 230 of Figure 2).
If desired, bearing support plate 295 may have long holes 320a, 320b,
320c for receiving one end 242, 245, 248 of respective input shafts
240, 243, 246.
Date Recue/Date Received 2020-10-16
24
Illustratively, at least two threaded holes 310 may be associated
with each long hole 320a, 320b, 320c. If desired, the at least two
threaded holes 310 may be located at different distances from output
shaft 230.
As shown in Figure 3, two pairs of threaded holes 310 is
associated with a predetermined distance from hole 330 and placed on
the sides of long holes 320a, 320b, 320c. However, bearing support
plate 295 may have more than two pairs of threaded holes 310
associated with a predetermined distance from hole 330. If desired,
bearing support plate 295 may have threaded holes 310 aligned with
hole 330 and respective long holes 320a, 320b, 320c. As an example,
bearing support plate 295 may have threaded holes 310 between hole
330 and respective long holes 320a, 320b, 320c. As another example,
bearing support plate 295 may have threaded holes 310 on the
opposite side of respective long holes 320a, 320b, 320c as in the
previous example.
Tensioners 272, 275, 278 may be attached to bearing support
plates 295 at the corresponding threaded holes 310. Thereby,
tensioners 272, 275, 278 may be moved to a respective preferred
position by moving respective input shafts 240, 243, 246 through
respective long holes 320a, 320b, 320c before the respective
tensioners 272, 275, 278 are tightened respectively fixed at this
position using one of the at least two threaded holes 310 for each
tensioner 272, 275, 278.
If desired, tensioners 272, 275, 278 or tensioners 271, 274, 277
may be attached to a structural part of an aircraft to which thrust
producing unit 200 is attached.
Date Recue/Date Received 2020-10-16
25
If desired, bearing support plate 290 and/or bearing support
plate 295 may be attached a structural part of an aircraft to which
thrust producing unit 200 is attached. Figure 4A is a diagram of an
illustrative thrust producing unit that has at least one bearing support
plate 290 or 295 attached to an aircraft structure 440.
Consider the scenario in which only one of bearing support
plates 290, 295 is attached to aircraft structure 440. In this scenario,
the thrust producing unit may include ribs that transfer the torque
generated by electric motors 280, 283, 286 to the other bearing
support plate of bearing support plates 290, 295. In case both bearing
support plates 290 and 295 are attached to aircraft structure 440 the
ribs may be omitted.
If desired, the thrust producing unit may have at least two
electric motors 280, 283 arranged at a same distance from the output
shaft. For example, thrust producing unit 200 of Figure 2 may have
three electric motors 280, 283, 286 arranged at an equal distance from
output shaft 230.
However, electric motors 280, 283, 286 may be arranged at
different distances from output shaft 230. Figure 4B is a diagram of an
__ illustrative thrust producing unit with three aligned electric motors 280,
283, 286. Aligning electric motors 280, 283, 286, especially in forward
flight direction, may reduce the aerodynamical drag caused by the
respective electric motors 280, 283, 286. If desired, electric motors
280, 283, 286 may be aligned with output shaft 230.
Illustratively, electric motor 280 is arranged at a first distance
410 from output shaft 230 and electric motors 283, 286 are arranged
at a second distance 420, 430 from output shaft 230, respectively. The
Date Recue/Date Received 2020-10-16
26
second distance may be selected to be different than the first
distance. For example, the second distance 420, 430 may be at least
two times greater than the first distance 410.
It should be noted that modifications to the above described
embodiments are within the common knowledge of the person skilled
in the art and, thus, also considered as being part of the present
invention.
For instance, electric motors 280, 283, 286 of Figure 3 drive the
upper, lower, and middle freewheel belt pulley 260, 263, 266,
respectively. However, any other appropriate combination of electric
motors 280, 283, 286 driving a particular freewheel belt pulley 260,
263, 266 may be selected instead. For example, electric motors 280,
283, 286 may drive lower, middle, and upper freewheel belt pulley 263,
266, 260, respectively.
Furthermore, fail-safe electrical drive unit 220 of Figure 3 may
be modified and/or include different components as shown without
changing its functionality. As an example, by changing the shape of
bearing support plates 290, 295, electric motors 280, 283, 286 may be
placed closer to respective fixedly attached belt pulleys 250, 253, 256,
thereby reducing the length of respective input shafts 240, 243, 246.
Date Recue/Date Received 2020-10-16
27
Reference List
100 aircraft
102 aircraft airframe, fuselage
102a aircraft airframe internal volume
103 thrust producing units
103a, 103b thrust producing unit
104 thrust producing units support structure
104a, 104b thrust producing units support structure member
105a, 105b fail-safe electrical drive unit
106 shrouding units
106a, 106b shrouding
108 rotor assemblies
108a, 108b rotor assembly
113 outer shell
200 thrust producing unit
210 rotor
212 rotor hub
213 rotor head
214 rotor support
Date Recue/Date Received 2020-10-16
28
215a, 215b rotor blade
220 fail-safe electrical drive unit
230 output shaft
231, 232 end of output shaft
240, 243, 246 input shaft
241, 242, 244, 245, 247, 248 end of input shaft
250, 253, 256 fixedly attached belt pulley
260, 263, 266 freewheeling belt pulley
261, 264, 267 freewheel
270, 273, 276 belt
271, 272, 274, 275, 277, 278 tensioners
280, 283, 286 electric motor
290, 295 bearing support plate
298 ribs
310 threaded hole
320a, 320b, 320c long hole
330 hole
410, 420, 430 distance
440 aircraft structure
Date Recue/Date Received 2020-10-16
