Drive system for a rotary-wing aircraft

Abstract

The invention relates to a drive system for a rotary-wing aircraft (10), comprising: a main drive unit (7) which is configured to generate a power with which a main rotor (1) of the rotary-wing aircraft (10) can be driven, a main transmission (6) which is configured to translate power generated by the main drive unit (7) into a torque acting on the main rotor (1), an additional or emergency drive unit (2) which is also configured to generate a power for driving the main rotor (1), wherein the additional or emergency drive unit (2) is designed to be connectable to the main transmission (6) via a switchable coupling unit (3). The invention also relates to a rotary-wing aircraft (10) comprising a drive system of this kind.

Description

[0001] Propulsion system for a rotary-wing aircraft

[0002] Technical area:

[0003] The invention relates to a drive system for a rotary-wing aircraft, in particular a helicopter, and to such a rotary-wing aircraft.

[0004] Technical background:

[0005] Rotary-wing aircraft, especially helicopters, can be subject to increased safety requirements in the event of a loss of engine power or a complete failure of a main propulsion unit. Single-engine helicopters, with exceptional pilot skill, can perform safe emergency landings using autorotation in the familiar manner. However, their use, especially in densely populated or otherwise critical areas, is severely restricted in practice by regulations (e.g., European aviation law regarding helicopter operations), because in such cases, access to suitable landing sites is more difficult.

[0006] Many helicopter types are therefore often equipped with two essentially identical and powerful main engines, which operate outside their optimal operating point. In an emergency, the remaining engine then powers the helicopter alone.

[0007] When weighing up cost-effectiveness against compliance with legal requirements and regulations, helicopter types that are also interesting are those equipped with, for example, only a single main propulsion unit and an additional auxiliary propulsion unit that can be used in an emergency. Due to the improved storage options in recent years, auxiliary propulsion systems based on electric motors are increasingly being considered. US 2019 / 0352001 A1 describes a propulsion system for a helicopter with only one propulsion engine. For use in emergency situations, an auxiliary propulsion device is provided that is physically integrated into a turboshaft main engine and forms a single unit with it. The auxiliary propulsion unit is mechanically connected to a rear drive train that extends between a one-way clutch (for power transmission from the main engine to the drive train) and the tail rotor gearbox.Emergency propulsion across the entire drivetrain occurs when the rotation generated by the auxiliary propulsion engine is greater than that generated by the main propulsion engine (e.g., in the event of engine failure) or in the event of autorotation. The auxiliary propulsion engine can be based on an electric drive, among other things.

[0008] US 2022 / 0388673 A1 describes the coupling of an electric motor to the main rotor of a helicopter via a reduction gear consisting of gears of the main gearbox.

[0009] US 2021 / 0229826 A1 describes a rotorcraft equipped with an engine and an assistance system with an electric motor that is deployed in an emergency. The electric motor is coupled to a secondary input of the main gearbox via a connection module.

[0010] US 2020 / 0277072 A1 discloses a method for assisting a pilot of a single-engine rotorcraft during an autorotation flight phase, wherein the rotorcraft comprises a hybrid propulsion unit with a main engine and an electric motor. The operation of the main engine is monitored during flight to detect a power loss on the main rotor and then control the electric motor to supply additional power to the main rotor.

[0011] US 2020 / 0283139 A1 proposes a hybrid propulsion system in which, for example, a main propulsion unit for operating the main rotor is provided by an internal combustion engine or an electric motor, while the tail rotor is driven by a separate motor that is operated hydraulically, electrically or pneumatically.

[0012] The patent US 10,759,280 B2 proposes various coupling options for an electric motor in a hybrid drive system, for example on the drive train coupled to the main engine, directly on the main gearbox or on the main rotor shaft extending from the main gearbox.

[0013] In the documents EP 4 015 377 A1 and

[0014] WO 2021 / 151873 A1 also describes hybrid drive systems. EP 3 921 231 B1 proposes integrating an electric motor into at least one planetary gear.

[0015] In most of the aforementioned proposals, the electric auxiliary drives are connected directly to the main transmission or to the respective drive trains coupled to it. Mechanical separation of the main drive unit from the respective auxiliary drive is generally achieved via a mechanical one-way clutch. However, the mechanical one-way clutch requires lubrication, which increases maintenance requirements, and allows torque to be transmitted in only one direction. Furthermore, due to the large number of sprags in the one-way clutch, a high number of moving parts is evident.

[0016] Furthermore, an auxiliary drive such as an electric motor is subject to the same high maintenance requirements as the other components of the drive system due to its direct connection to the main gearbox or drive train in order to ensure reliability, which increases the effort and costs for operation, even if the auxiliary drive is rarely used.

[0017] It is therefore a task to further improve existing drive system concepts and reduce the costs and effort for general operation. Description of the invention:

[0018] According to aspects of the invention which take into account one or the other of the aforementioned needs, a drive system for a rotorcraft, in particular for a helicopter, comprises a main drive unit which is configured to generate power with which a main rotor of the helicopter having a plurality of rotor blades can be driven, a main gearbox which is configured to translate the power generated by the main drive unit into a torque acting on the main rotor, and an additional or emergency drive unit which is also configured to generate power for driving the main rotor, wherein the additional or emergency drive unit is configured to be connectable to the main gearbox via a switchable clutch unit.

[0019] The mechanical main gearbox in a rotorcraft is used to transmit the engine's drive torque to the main rotor and, if coupled, a tail rotor at the correct speed. The main gearbox is designed to achieve maximum torque. This can pose particular problems if, for example, the main propulsion unit fails and additional torque is required.

[0020] For example, if the main propulsion unit is still transmitting residual power while a corresponding auxiliary drive is already engaged, this can lead to overloading and permanent damage to the gearbox. The same can also apply to stabilized autorotation flight. In this case, power is transferred from the main rotor to the main gearbox, into which the auxiliary drive also feeds power, which can therefore lead to overloading.

[0021] This problem is solved by the switchable clutch unit provided according to the invention. Unlike a one-way clutch, which only operates in one direction of rotation and is therefore neither controllable nor switchable, such a switchable clutch unit can be controlled and switched externally in a targeted and situation-dependent manner. The switchable clutch unit allows the auxiliary or emergency drive unit provided according to the aforementioned aspects to be connected to the main transmission in a controlled manner in such cases.

[0022] In particular, the onset of torque transmission from the auxiliary or emergency drive unit can be controlled in a targeted manner. For example, the (not necessarily instantaneous) switching process of the clutch unit can be carried out depending on the current load on the main transmission. According to exemplary embodiments, a sensor and / or computing network can be available for this purpose, with which current speeds in the main rotor, in the main transmission, and in the drive trains are recorded and the respective existing torques are calculated and compared with critical values. An auxiliary or emergency drive control unit provided according to further exemplary embodiments and described below can, on this basis, regulate the switching process of the switchable clutch unit and, in coordination with the control, also control the power generation in the auxiliary or emergency drive unit.

[0023] Thus, a switchable clutch enables a seamless transition from main drive via the main propulsion unit to auxiliary drive via the auxiliary or emergency propulsion unit without exceeding critical torque limits. According to the invention, this applies not only to emergencies in the event of failure or loss of power of the main propulsion unit, but also to merely supporting auxiliary drive via the auxiliary or emergency propulsion unit, because in such a case, the same problems of excessive torques fundamentally exist at the time of engagement. The same applies in the event of a power reversal, for example, if the auxiliary or emergency propulsion unit is an electric motor temporarily operated as an electric generator to charge a battery module.

[0024] In addition, the solution proposed here also enables a controllable, mechanical separation of the auxiliary or emergency propulsion unit from the main gearbox and the main propulsion unit during normal flight operations. This decouples the auxiliary or emergency propulsion unit from these components, and any malfunctions in this area do not directly affect the main gearbox. This somewhat reduces maintenance interval requirements, which can reduce operating costs and effort.

[0025] The main propulsion unit can be any type of engine, for example, a thermodynamic engine, in particular a shaft turbine, e.g., with a gas generator and power turbine, or a piston engine. Other types, including electric motors, are also possible. If the rotorcraft is a gyroplane, any type of traction or thrust engine can be provided. The implementation of two main propulsion units in the rotorcraft is also fundamentally encompassed by aspects of the invention.

[0026] The main rotor of the rotorcraft can be one with any number of rotor blades. The implementation of dual rotors can also be encompassed by aspects of the invention. Optionally, a tail rotor gearbox can also be coupled, but this is not mandatory for the implementation of the invention.

[0027] The switchable clutch unit comprises the actual clutch and control electronics. It advantageously replaces the overrunning clutch, which was previously the only coupling available for the auxiliary or emergency drive unit, and thus eliminates the aforementioned disadvantages of the same. The switchable clutch unit is designed to connect or disconnect the auxiliary or emergency drive unit from the main gearbox. The connection to the main gearbox can be made directly (via an input of the main gearbox) or indirectly via a drive train, which in turn is permanently coupled to the main gearbox. A connection to the main gearbox, for example, via a coupling to the rotor mast, is not excluded.

[0028] The invention is not limited to specific types of switchable clutches.

[0029] Examples include the multi-disk clutch, the pole friction clutch, the magnetic clutch, or the magnetic particle clutch. Of these, the pole friction clutch may be the most preferred because it is particularly suitable for the initially very high differential speeds. The pole friction clutch operates in dry or wet running. With this type, actuation occurs through a current flow and a developing magnetic field, and torque is transmitted through frictional engagement.

[0030] Alternatively, the multi-plate clutch mentioned above is also possible. This also operates in dry or wet mode. Here, the release lever is electronically activated to generate the contact pressure, while power is transmitted via an electromagnet. The torque is transmitted purely mechanically through friction.

[0031] Furthermore, the aforementioned magnetic clutch can also be used. The torque is transmitted solely via a magnetic field, making this type of clutch completely wear-free. In the case of the magnetic particle clutch, the torque is transmitted via stiffening magnetic powder particles. The clutch is triggered by a current flow, making variable torque particularly easy to achieve. Other switchable or controllable clutch types that enable a controlled clutch process are also conceivable.

[0032] The terms "switchable" and "controllable," referring to the clutch, are used synonymously in this application. This implies that the clutch can be selectively actuated from the outside to establish or disconnect a connection between the auxiliary or emergency drive unit and the main transmission, and that the clutch operation itself can be controlled, i.e., the degree of torque transmission can be controlled over time (which in practice may be quite short), e.g., through friction, etc., depending on the clutch type.

[0033] In a preferred embodiment, the auxiliary or emergency propulsion unit comprises an electric motor. This can more preferably be designed and dimensioned such that a main rotor and / or tail rotor of a rotary-wing aircraft, in particular a helicopter, can be driven autonomously and without an additional drive. For the purposes of the present invention, a self-sufficient electric drive is understood to mean that a mechanical output of preferably at least 80 kW, more preferably 100 kW to 700 kW, even more preferably 300 kW to 400 kW, and most preferably around 600 kW can be achieved. The electric motor can be a synchronous motor, but the invention is fundamentally not limited to specific types of motors.

[0034] Electric motors have high torque, low wear and tear and a very short latency until power is delivered, so that control in coordination with the clutch process is particularly advantageous.

[0035] In principle, several electric motors can also be provided.

[0036] According to a further development, a first battery module is provided, which is configured to supply the electric motor of the auxiliary or emergency propulsion unit with electrical energy. Battery types with high power density are preferred here. According to specific embodiments, the first battery module serves to supply the electric motor with energy in an emergency, e.g., in the event of engine failure or loss of power. For this purpose, the storage capacity of the first battery module is at least sufficient to achieve a flight range appropriate to the circumstances, to reach a suitable landing site, and, if necessary, in conjunction with autorotation, to enable a one-time safe landing.

[0037] An embodiment which includes the above-mentioned types of clutches accordingly provides that the switchable clutch unit is electromechanically and / or electromagnetically switchable in order to selectively connect the additional or emergency drive unit or the electric motor to the main transmission or to disconnect it from it.

[0038] According to a further development, the switchable clutch unit is designed to couple and uncouple a drive shaft of the electric motor with an auxiliary drive train. This auxiliary drive train is connected to an input of the main transmission. The power generated by the main drive unit can be fed to the main transmission via a main drive train. A special feature here is that the main drive train is connected to the same input of the main transmission as the auxiliary drive train. This aspect is particularly advantageous because the entire design is particularly simple and space-saving. The additional or emergency drive unit with the clutch can therefore be easily arranged opposite the main drive unit. The input of the main transmission can, for example, be formed by a sun gear that is operatively connected to a planetary gear of the main transmission.It has been found that in practice, in helicopters, for example, there is unused space above the passenger cabin (upper section of the fuselage) at the described location, which is now being put to good use. Existing bulkheads in this area often already have the necessary load-bearing capacity to mount the electric motor.

[0039] Another aspect concerns an additional or emergency drive control unit mentioned above. This is configured to actuate the electric motor and switch the switchable clutch unit, depending on an activation criterion, in order to connect the electric motor to or disconnect it from the main transmission.

[0040] According to a first embodiment of this aspect, the auxiliary or emergency drive control unit is connected to a drive sensor system to detect an existing or imminent failure of the main drive unit. It is configured to start the electric motor depending on the detection result as an activation criterion and to engage the clutch unit to connect the electric motor to the main transmission, so that the main rotor is driven by the power from the electric motor in emergency operation.

[0041] For this purpose, the drive sensor system may comprise one or more sensors for detecting at least one of the following values:

[0042] (a) Rotor speed,

[0043] (b) speed of a gas generator of the main propulsion unit,

[0044] (c) Speed ​​of a power turbine of the main propulsion unit, etc. From these components, the auxiliary or emergency propulsion control unit, as described above, can not only detect the emergency situation itself, such as the loss of power of the main propulsion unit, but also calculate or track the current torque ratios during the subsequent switching or control of the switchable clutch unit. The clutch process can thus be dynamically adjusted depending on a currently detected and calculated torque compared to a predefined critical torque.

[0045] However, this control is not only possible in the case of emergency operation, but also in generator operation. For example, a second battery module can be provided which is configured to supply the electric motor of the auxiliary or emergency drive unit with electrical energy, wherein the auxiliary or emergency drive control unit is connected to a battery sensor system in order to detect a low battery charge state in the first and / or the second battery module. Furthermore, it is configured to switch the clutch unit depending on the detection result as an activation criterion in order to connect the electric motor to the main transmission and to operate it as a generator in generator operation in order to charge the second battery module with a portion of the power of the main drive unit converted into electrical power.

[0046] In contrast to the first battery module, which cannot be charged during flight operations, the second battery module can be charged during flight operations. Thus, the first battery module is designed for emergency operation only in a secure environment and therefore meets the increased safety requirements. The second battery module, on the other hand, can be used specifically to support ongoing flight operations (hereinafter referred to as auxiliary operation). However, it does not have to meet the very high safety requirements and requires correspondingly less maintenance, as it is not critical to flight operations.

[0047] Accordingly, a further embodiment provides for the additional or

[0048] An emergency propulsion control unit is configured to connect to a pilot control unit, wherein the pilot control unit has an input device and is configured to generate an input signal dependent on a pilot input to the input device and to transmit it to the auxiliary or emergency propulsion control unit. The auxiliary or emergency propulsion control unit is further configured to start the electric motor dependent on the transmitted input signal as an activation criterion and to switch the clutch unit to connect the electric motor to the main transmission, so that in auxiliary operation, the main rotor is driven by power from the electric motor in addition to the power from the main drive unit.

[0049] The auxiliary or emergency propulsion control unit can be configured, as described, to perform auxiliary operation using the electric motor based exclusively on a power supply from the second battery module. The energy stored in the first battery module is reserved exclusively for emergency use, i.e., the first battery module does not need to be connected to any electrical consumers other than the electric motor and the auxiliary or emergency propulsion control unit, as well as the corresponding battery sensors. Charging or replacing the battery only occurs during ground maintenance.

[0050] According to a further, non-limiting, specific embodiment of the invention already indicated above, the main propulsion unit, the main gearbox, and the auxiliary or emergency propulsion unit can be arranged substantially along a longitudinal axis of the rotorcraft, with the auxiliary or emergency propulsion unit and the main propulsion unit being arranged on opposite sides of the main gearbox. The auxiliary or emergency propulsion unit is preferably arranged in front of the main gearbox in the intended flight direction of the rotorcraft. This results in the described advantages. However, mounting the engine and the clutch laterally on the main gearbox is also not excluded in principle.

[0051] The invention also relates to a rotary-wing aircraft, in particular a helicopter, comprising a propulsion system according to one of the preceding aspects, embodiments or examples, or further developments. The auxiliary or emergency propulsion unit can advantageously be arranged in a space above a payload or passenger compartment provided in a cabin, in particular above a passenger compartment.

[0052] Furthermore, the invention also relates to a use of the drive system in a rotary-wing aircraft, in particular a helicopter.

[0053] Features, expediencies and advantages of the invention are described below using exemplary embodiments with reference to the drawings.

[0054] Short the

[0055] They show:

[0056] Fig. 1 is a schematic representation of a rotorcraft or helicopter with a propulsion system according to an exemplary embodiment of the invention;

[0057] Fig. 2 is a system drawing of the drive system according to Fig. 1;

[0058] Fig. 3 is a schematic representation of a control network providing the auxiliary or emergency drive with the auxiliary or emergency drive control unit shown in Fig. 2 as the central controller;

[0059] Fig. 4 shows a schematic representation of a control system in emergency mode;

[0060] Fig. 5 like Fig. 4, but for additional operation (Power Boost Mode);

[0061] Fig. 6 like Fig. 4 or 5, but for generator operation (Power Generator Mode): Fig. 7 a side view of the drive system (without main drive unit);

[0062] Fig. 8 shows a cross-section through the drive system (without main drive unit).

[0063] Detailed description of preferred embodiments:

[0064] In the following description of preferred embodiments, it should be noted that the present disclosure of the various aspects is not limited to the details of the construction and arrangement of the components as shown in the following description and in the figures. All embodiments, even those not shown in the figures, can be practiced or carried out in various ways. It should also be noted that the phraseology and terminology used herein is used for the purpose of specific description only and should not be construed as such by one skilled in the art.Furthermore, in the following description, the same reference numerals in the figures denote the same or similar features or objects, so that in some cases a repeated detailed description of the same is omitted in order to maintain the compactness and clarity of the illustration.

[0065] Fig. 1 shows a rotorcraft 10, here a helicopter, with a propulsion system according to one embodiment of the present invention. The rotorcraft 10 has a main rotor 1, equipped, for example, with two rotor blades, and a tail rotor 99. The main rotor 1 and the tail rotor 99 are driven by a main propulsion unit 7. The main propulsion unit 7 is, for example, a shaft power turbine with a gas generator and power turbine. In order to convert a high speed of the power turbine, for example 6800 revolutions / min, into high torque, a reducing main gearbox 6 is installed. The main rotor 1 is ultimately operated with high torque at only a reduced speed, for example 350 revolutions / min. The tail rotor 99 is rotated in a coordinated manner via a drive train 8, which connects the main gearbox 6 to a tail rotor gearbox 9.

[0066] The drive system of the helicopter shown in Figure 1 further comprises an auxiliary or emergency drive unit 2, which is in particular an electric motor 21, for example a synchronous motor. The auxiliary or emergency drive unit 2 is connected to a first battery module 4 and a second battery module 5, respectively, so that they can selectively provide electrical energy for operating the auxiliary or emergency drive unit 2. The auxiliary or emergency drive unit 2 can be connected to or disconnected from the main transmission 6 via a switchable clutch unit 3 in order to implement various operating modes of the helicopter, which are described below with reference to Figures 4-6.

[0067] Figure 2 shows a schematic overview of the drive system from Figure 1 in greater detail. Power is transmitted from the main drive unit 7 via a one-way clutch 72, which disconnects the main drive unit 7 from the drive train 8 when the corresponding speed, reduced by the intermediate gear 71, falls below that of the drive train 8. During normal operation, the drive torque is transmitted to the main gear 6, where the high torque for the main rotor 1 is generated.

[0068] On the other hand, Figure 2 shows that the provision of electrical energy from the battery modules 4 and 5, the operation of the auxiliary or emergency drive unit 2 (i.e., the electric motor) and the switchable clutch unit 3 are controlled or regulated by an auxiliary or emergency drive control unit 35.

[0069] A network assigned to the auxiliary or emergency propulsion control unit 35 is shown in greater detail in Figure 3. In this exemplary embodiment, the auxiliary or emergency propulsion control unit 35 is connected to an extensive sensor system that allows evaluation of the current state of the propulsion system. Dashed arrows represent input from sensors 11, 74, and 75 of the propulsion system actively running during normal operation. In particular, these are a speed sensor 11 for the main rotor, a speed sensor 74 for the power turbine, and a speed sensor 75 for the gas generator. These sensors can be designed as desired. Such sensors are generally also present in conventional helicopters, so that the intervention in the existing system for implementing the invention is minimal.Based on the detected speeds supplied by the sensors 11, 74 and 75, the additional or emergency drive control unit 35 can evaluate the presence of a critical condition by comparing it with predetermined critical values ​​(activation criterion).

[0070] In addition, the auxiliary or emergency drive control unit 35 can also calculate the torque acting in the individual components based on the transmitted speeds and also compare them with predetermined critical limit torques.

[0071] Furthermore, the auxiliary or emergency drive control unit 35 is connected to a sensor / actuator 22 for the electric motor 21, which, for example, detects its speed and / or phase position and transmits it to the auxiliary or emergency drive control unit 35 or controls the motor power, and to a sensor / actuator 31 for the clutch unit 3, which provides data on its switching state and position (bold arrows in Fig. 3) and switches the clutch unit 3. The transmitted data allows the auxiliary or emergency drive control unit 35 to determine the torque currently transmitted from the electric motor 21 to the main transmission 6. Control via the actuators allows precise control of the engine start and clutch process.In this way, appropriate control of the transition from main operation (only the main drive unit supplies power) to emergency, auxiliary or generator operation can be carried out.

[0072] The implementation of emergency operation 200 is shown schematically in Figure 4. In

[0073] Step 202 is performed as described above by the additional or

[0074] Emergency drive control unit 35 determines whether a power loss has occurred ("Y") and thus emergency operation must be initiated (evaluation of the data from sensors 11, 74, or 75). In step 204, the auxiliary or emergency drive control unit 35 first starts the electric motor 21 and then, in step 206, activates the clutch unit 3 to establish a connection between the electric motor 21 and the main transmission 6 (actuation of the actuators 22 and 31). In step 208, the status of the acting torques is checked (evaluation of the data from sensors 11, 22, 31, 74, and / or 75). In step 210, the torques calculated in this way are compared with limit torques, and in step 212, feedback is provided to adjust the operation of the electric motor 21 and the clutch unit 3 in a control loop.

[0075] After a safe landing, the connection between the electric motor 21 and the main gearbox 6 can be separated again (open the clutch) to allow the main rotor 1 to rotate.

[0076] The above-mentioned auxiliary operation 300 is shown in Figure 5. The basic process sequence is very similar to that of emergency operation, i.e., the clutch operation is controlled in a control loop to monitor the torque. In step 302, auxiliary operation 300 is activated via an input device of a pilot control 101 shown in Figure 3. More precisely, a recurring check is performed to determine whether the corresponding signal ("Y") is present. Before auxiliary operation is actually carried out, a check is performed in step 303 to determine whether there is still sufficient stored energy in the second battery module 5 (see battery sensor 51 connected to auxiliary or emergency drive control unit 35 in Figure 3) to carry out auxiliary operation.If this is the case ("Y"), in steps 304-312, control of the electric motor 21 and the clutch unit 3 is carried out in a manner analogous to Figure 4 in order to prevent damage due to excessive torque.

[0077] The generator operation 400, also mentioned above, is shown in Figure 6. The event initiating the generator operation 400 is when the state of charge of the second battery module five falls below a predetermined value, wherein the currently recorded values ​​are regularly read out by the additional or emergency drive control unit 35 from the battery sensor 51 (see Figure 3) and compared with the predetermined limit value (step 401). In step 402, a check is carried out to determine whether there is a drop in power or failure of the main drive unit. In this case, it must be ensured that the electric motor 21 of the additional or emergency drive unit is quickly available for transmitting drive torque. If this is not the case, then in step 406 the clutch unit 3 is first actuated and then the electric motor 21 orThe auxiliary or emergency drive unit 2 is switched to generator mode to charge the second battery module 5. The coupling process is checked for excessive torque in the control loop analogous to Figure 4 or 5.

[0078] It should be noted that the auxiliary or emergency drive control unit 35 can also check the battery charge level of the first battery module 4 through the corresponding battery sensor 41, as shown in Figure 3.

[0079] Figure 7 shows a side view of the main gearbox 6 with rotor mast 66 and the additional or emergency drive unit 2 connected to the main gearbox 6. Figure 8 shows the corresponding cross-section. The electric motor 21 has a motor shaft 32 which can be used with an auxiliary drive train 33 of the main gearbox 6 via the switchable clutch unit 3. The cross-section of Figure 8 shows that the auxiliary drive train 33 and the main drive train 8 engage at the same input in the main gearbox 6, which is formed by the sun gear 63. The auxiliary drive train 33 has a toothing 34 for this purpose, and the main drive train 8 has a toothing 81 for this purpose. The sun gear 63, in turn, interacts with a first stage 64 of a planetary gear provided in the main gearbox 6.A second stage 65 of the planetary gear finally leads to a further reduction in the gear ratio and an increase in the torque, which is ultimately transmitted to the rotor mast 66 via elements not shown in further detail but known to those skilled in the art. An exemplary structure of a main gear 6 that can be implemented, which does not limit the present invention, is disclosed, for example, in EP 3 323 718 A1. Other main gear concepts are also possible.

[0080] The above-mentioned embodiments relate to a helicopter. However, the principles of the invention can also be applied analogously to other rotary-wing aircraft, such as gyrocopters or quadrocopters, etc.

[0081] List of

[0082] 1 main rotor

[0083] 11 Main rotor speed sensor

[0084] 2 Additional or emergency power unit

[0085] 21 electric motor

[0086] 22 Sensor / actuator for electric motor (speed and / or phase position)

[0087] 3 switchable clutch unit

[0088] 31 Sensor / actuator for clutch unit (switching state and position)

[0089] 32 Motor shaft (electric motor)

[0090] 33 Auxiliary drive train

[0091] 34 Gearing, bevel gear

[0092] 35 Auxiliary or emergency drive control unit

[0093] 4 first battery module, not rechargeable during flight

[0094] 41 Sensor for first battery module (state of charge, temperature, voltage, etc.)

[0095] 5 second battery module, rechargeable during flight

[0096] 51 Sensor for second battery module (state of charge, temperature, voltage, etc.)

[0097] 6 main gearboxes

[0098] 63 Entrance, sun gear

[0099] 64 planetary gear, 1st stage

[0100] 65 Planetary gear, 2nd stage

[0101] 66 Rotor mast

[0102] 7 Main drive unit

[0103] 71 intermediate gear

[0104] 72 Overrunning clutch

[0105] 74 Speed ​​sensor for power turbine

[0106] 75 Speed ​​sensor for gas generator

[0107] 8 Main drive train

[0108] 81 Gearing, bevel gear

[0109] 9 tail rotor gearbox

[0110] 99 tail rotor

[0111] 10 rotary-wing aircraft, helicopters

[0112] 101 Pilot control, with input device Emergency operation (start) Auxiliary operation (start) Generator operation (start)

Claims

Claims: 1 . A drive system for a rotorcraft (10), comprising: a main drive unit (7) configured to generate power with which a main rotor (1) of the rotorcraft (10) having a plurality of rotor blades can be driven, a main gearbox (6) configured to translate the power generated by the main drive unit (7) into a torque acting on the main rotor (1), an additional or emergency drive unit (2) likewise configured to generate power for driving the main rotor (1), wherein the additional or emergency drive unit (2) is configured to be connectable to the main gearbox (6) via a switchable clutch unit (3).

2. Drive system according to claim 1, wherein the additional or emergency drive unit (2) comprises an electric motor (21), and wherein the main drive unit (7) preferably comprises a thermodynamic engine.

3. Drive system according to claim 2, further comprising: a first battery module (4) which is configured to supply the electric motor (21) of the auxiliary or emergency drive unit (2) with electrical energy.

4. Drive system according to claim 3, wherein the switchable clutch unit (3) is electromechanically and / or electromagnetically switchable in order to selectively connect the additional or emergency drive unit (2) or the electric motor (21) to the main transmission (6) or to disconnect it therefrom.

5. Drive system according to one of claims 3 to 4, wherein the switchable clutch unit (3) is configured to couple and uncouple a drive shaft (32) of the electric motor (21) to an auxiliary drive train (33), the auxiliary drive train (33) is connected to an input of the main transmission (6), the power generated by the main drive unit (7) is supplied to the main transmission (6) via a main drive train (8), and the main drive train (8) is connected to the same input (63) of the main transmission (6) as the auxiliary drive train (33).

6. Drive system according to claim 5, wherein the input (63) of the main gear (6) is formed by a sun gear which is in operative relationship with a planetary gear (64, 65).

7. Drive system according to one of claims 3 to 6, further comprising: an additional or emergency drive control unit (35) which is configured to actuate the electric motor (21) and to switch the switchable clutch unit (3) depending on an activation criterion in order to connect the electric motor (21) to the main transmission (6) or to disconnect it from it.

8. Drive system (10) according to claim 7, wherein the additional or emergency drive control unit (35) is connected to a drive sensor system (22, 31, 11, 74, 75) in order to detect an occurred or imminent failure of the main drive unit (7) and is set up to start the electric motor (21) depending on the detection result as an activation criterion and to switch the clutch unit (3) in order to connect the electric motor (21) to the main transmission (6) so that the main rotor (1) is driven in an emergency operation (200) with the power from the electric motor (21).

9. Drive system according to claim 8, wherein the drive sensor system (22, 31, 11, 74, 75) comprises one or more sensors for detecting at least one of the following: (a) Rotor speed, (b) speed of the gas generator, (c) speed of the power turbine, 10. Drive system according to one of claims 7 to 9, further comprising a second battery module (5) which is configured to supply the electric motor (21) of the auxiliary or emergency drive unit (2) with electrical energy, wherein the auxiliary or emergency drive control unit (35) is connected to a battery sensor system (41, 51) in order to detect a low battery charge state in the first and / or the second battery module (4, 5), and is configured, depending on the detection result as an activation criterion, to switch the clutch unit (3) in order to connect the electric motor (21) to the main transmission (6) and to operate it as a generator in a generator mode (400) in order to charge the second battery module (5) with a part of the power of the main drive unit (7) converted into electrical power.

11. A drive system according to claim 10, wherein the first battery module (4) is configured so that it cannot be charged during flight operation; and the second battery module (5) is configured so that it can be charged during flight operation.

12. Drive system according to one of claims 7 to 11, wherein the additional or emergency drive control unit (35) is connected to a pilot control unit (101), wherein the pilot control unit (101) has an input device and is designed to generate an input signal depending on an input of a pilot into the input device and to transmit it to the additional or emergency drive control unit, wherein the additional or emergency drive control unit is designed to start the electric motor depending on the transmitted input signal as an activation criterion and to switch the clutch unit (3) in order to connect the electric motor (21) to the main transmission (6), so that the Main rotor (1) is driven in an additional mode (300) in addition to the power provided by the main drive unit (7) by power from the electric motor (21).

13. Drive system (10) according to claim 12 with reference to one of claims 10 or 11, wherein the auxiliary or emergency drive control unit (2) is arranged to carry out the auxiliary operation (300) by means of the electric motor (21) on the basis of a power supply exclusively from the second battery module (5).

14. Drive system according to one of the preceding claims, wherein the first battery module (4) is not connected to any electrical consumer except for the electric motor (21) and the additional or emergency drive control unit (35) and corresponding battery sensors.

15. Propulsion system according to one of the preceding claims, wherein the main propulsion unit (7), the main gearbox (6) and the additional or emergency propulsion unit (2) are arranged substantially along a longitudinal axis of the rotorcraft (10), wherein the additional or emergency propulsion unit (2) and the main propulsion unit (7) are arranged on opposite sides with respect to the main gearbox (6), wherein the additional or emergency propulsion unit (2) is preferably arranged in front of the main gearbox (6) in the intended flight direction of the rotorcraft (10).

16. A rotary-wing aircraft (10), in particular a helicopter, comprising a drive system according to one of the preceding claims, wherein the additional or emergency drive unit (2) is arranged in a space above a payload receiving space provided in a cabin, in particular above a passenger compartment.

17. Use of a drive system according to one of claims 1 to 15 in a rotorcraft, in particular a helicopter.

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