Hybrid drive system for an aircraft

Abstract

The invention relates to a hybrid drive system (1) for an aircraft. A gas turbine engine (2) is designed to drive an engine output shaft (10) which can be connected to a planetary gearbox (4) via a freewheel (16). An electric machine (3) is designed to drive a machine output shaft (18) which can be operatively connected to the planetary gearbox (4) via a clutch (20). A gear unit (5) comprises an input shaft (11) and an output shaft (14), the input shaft (11) extending radially offset with respect to the output shaft (14) and coaxially with respect to the engine output shaft (10). The input shaft (11) can be connected to the engine output shaft (10) via the freewheel (16), and the output shaft (14), which is arranged coaxially with respect to the machine output shaft (18), can be connected to the planetary gearbox (4). Alternatively, the output shaft (14) may be connectable, via the freewheel (16), to the planetary gearbox (4) by means of a further shaft (19) which extends coaxially with respect to the machine output shaft (18), and the input shaft (11) may be connected coaxially to the engine output shaft (10).

Description

[0001] Hybrid propulsion system for an aircraft

[0002] The present disclosure relates to a hybrid propulsion system for an aircraft comprising a gas turbine engine, an electric machine, a gearbox unit and a planetary gearbox.

[0003] A hybrid-electric drive system with a gas turbine engine is known from US patent 10,837,304 B2. The drive system further comprises a drive shaft, an electric machine coupled to the drive shaft, and an internal combustion engine with an output shaft. Additionally, a freewheel clutch is provided, which is connected to at least one of the drive shafts and the output shaft of the internal combustion engine. The freewheel clutch either locks the drive shaft and the output shaft together or disconnects them, depending on the direction of rotation.

[0004] A hybrid propulsion system for an aircraft is described in US Patent 10,981,660 B2. The hybrid propulsion system comprises a propulsor and a gas turbine engine, which drives the propulsor in a first operating mode. Additionally, the hybrid propulsion system includes an electric motor, which drives the propulsor in a second operating mode. The propulsor can be, for example, a fan or a propeller.

[0005] A coupling is provided between the gas turbine engine and the electric motor, allowing the connection between an output shaft of the gas turbine engine and the drive shaft of the electric motor, which is connected to the propulsor, to be disengaged. The coupling can, for example, be designed as a freewheel.

[0006] Furthermore, US Patent 11,732,639 B2 discloses an aircraft engine with a hybrid-electric propulsion system. The propulsion system comprises a heat engine with a heat engine shaft and an electric motor with a motor shaft. Additionally, a transmission system is provided, which converts the input drive torques of the heat engine and the electric motor accordingly and outputs them as output torque. The motor shaft is equipped with a disconnect mechanism by which the operative connection between the motor shaft and the transmission system can be disconnected, allowing the heat engine to operate freely when the electric motor is switched off. The heat engine shaft is also equipped with a disconnect mechanism by which the operative connection between the heat engine shaft and the transmission system can be released, allowing the electric motor to operate freely when the heat engine shaft is stationary.

[0007] The present disclosure is based on the objective of further developing existing hybrid propulsion systems for aircraft in an advantageous manner.

[0008] This problem is solved with a hybrid drive system having the features of claim 1.

[0009] The hybrid propulsion system for an aircraft according to the present disclosure comprises a gas turbine engine configured to drive an engine output shaft. The engine output shaft can be connected to a planetary gearbox via a freewheel. Additionally, an electric motor is provided, configured to drive a motor output shaft. The motor output shaft can be operatively connected to the planetary gearbox via a coupling.

[0010] A gearbox unit is designed with an input shaft and an output shaft. The input shaft is offset from the output shaft and coaxial with the engine output shaft. In a first embodiment of the hybrid drive system, the input shaft of the gearbox unit can be connected to the engine output shaft via the freewheel, and the output shaft of the gearbox unit, which is arranged coaxially with the engine output shaft, is connected to the planetary gear set.

[0011] In an alternative embodiment of the hybrid drive system, the output shaft of the gearbox unit can be connected to the planetary gearbox via the freewheel and an associated additional shaft. This additional shaft runs coaxially to the machine's output shaft, while the input shaft of the gearbox unit is connected to the engine's output shaft.

[0012] The freewheel mechanism allows a fan or propeller of an aircraft engine to be driven simultaneously by the gas turbine engine and the electric motor during takeoff or climb, without any additional actuation effort.

[0013] If, on the other hand, a fan or propeller is to be driven solely by the electric motor with the gas turbine engine switched off, the freewheel automatically decouples the gas turbine engine from the planetary gearbox as soon as the switching element half of the freewheel connected to the planetary gearbox rotates faster than the switching element half of the freewheel connected to the engine output shaft. This ensures, with minimal effort, that the electric motor can then be driven independently of the operating state of the gas turbine engine.

[0014] In contrast, when open, the clutch allows the operative connection between the electric machine and the planetary gearbox to be disconnected. In this state, only the drive torque of the gas turbine engine is applied to the planetary gearbox, which can then operate independently of the electric machine's operating state. Positioning the gearbox unit between the electric machine and the gas turbine engine allows for a simple radial arrangement of the engine output shaft within the hybrid drive system with a defined axial offset relative to the electric machine's output shaft. This enables a staggered arrangement between the gas turbine engine and the electric machine, which are positioned axially one behind the other.This makes it possible to adapt the hybrid propulsion system to existing installation spaces within an aircraft with minimal effort, which has an overall positive effect on the specific fuel consumption of an aircraft equipped with the hybrid propulsion system.

[0015] The combination of the gearbox unit and the planetary gearbox offers the possibility of connecting the gas turbine engine to, for example, a propeller via a high reduction ratio, in order to operate both the propeller and the gas turbine engine within efficiency-optimal speed ranges and to design the drive system with the lowest possible overall weight.

[0016] In an embodiment of the hybrid drive system characterized by a small installation space requirement in the radial direction, the output shaft of the gearbox unit and the other shaft run coaxially to each other.

[0017] In an embodiment of the hybrid drive system according to the present disclosure that is also space-saving in the radial direction, the further shaft or the output shaft can extend axially through the machine output shaft from the gear unit towards the planetary gear.

[0018] Furthermore, it can be provided that the secondary shaft or the output shaft is connected to a first switching element half of the coupling, which can be engaged with a second switching element half of the coupling. The second switching element half of the coupling can be connected to the machine output shaft. Additionally, it is possible that the machine output shaft can be connected to the secondary shaft or to the output shaft via the coupling.

[0019] If the shaft or output shaft is connected to a planetary gear shaft, which can be configured as a sun gear, ring gear, or planet carrier, the high-power-density drive torque of the gas turbine engine can be converted or transformed via the planetary gear such that a propeller or fan connected to an output shaft of the planetary gear can be driven with a correspondingly high torque. Furthermore, the gas turbine engine can then be designed with a correspondingly lower torque, which in turn has a positive effect on the external dimensions and component weight of the gas turbine engine.

[0020] The planetary gear can be designed as a simple planetary gear set and preferably with a non-rotating or rotatable planet carrier, and the gear ratio of the planetary gear can each have values ​​in a gear ratio range of 2.3:1 to 8.0:1.

[0021] Additionally, the planetary gear set can comprise at least two simple planetary gear sets connected in a back-to-back arrangement, with their planet carriers preferably being either rotationally fixed or rotatable. The gear ratios of the simple planetary gear sets can each have values ​​ranging from 2.3:1 to 8.0:1.

[0022] In a further embodiment of the hybrid drive system according to the present disclosure, the additional shaft or output shaft can be connected to a rotatable first shaft of the planetary gear set, which may be configured as a sun gear, ring gear, or planet carrier. If a first switching element half of the coupling, which is connected to the machine output shaft, is operatively connected to a second switching element half of the coupling, which is rotationally fixed to a second shaft of the planetary gear set, which may be configured as a sun gear, ring gear, or planet carrier, the drive torque of the gas turbine engine and the electric machine can again be converted accordingly in a structurally simple manner. Then, a fan or propeller connected to an output shaft of the planetary gear set can be driven with high drive torque.The gas turbine engine can then be manufactured with a correspondingly lower power output, which has a positive effect on the component weight and the manufacturing costs of the gas turbine engine.

[0023] The planetary gear can be designed as a stepped planetary gear with at least one stepped planet having two gear sections, wherein a planet carrier can be fixed to the housing or rotatable. The pitch circle diameters of the gear sections can differ, with a first gear section engaging with a shaft of the planetary gear, which is preferably designed as a non-rotating ring gear.

[0024] The gear ratio of a stepped planetary gear set can have values ​​in a ratio range from 4.0:1 to 20:1.

[0025] The first gear section of the stepped planetary gear can engage with the second shaft of the planetary gear.

[0026] A second gearing area of ​​the stepped planetary gear can engage with the shaft, which is connected to the further shaft or the output shaft.

[0027] The pitch circle diameter of the first gear section can be either smaller or larger than the pitch circle diameter of the first gear section, depending on the specific application. The design of the pitch circle diameters of the gear sections and the coupling of the stepped planetary gearbox to the input shaft(s) and the output shaft are also determined, in particular, by the speed range of the electric machine within which it can be operated with high efficiency.

[0028] The gear section of the stepped planet gear, whose pitch circle diameter is larger, can engage with the sun gear, to which the other shaft or the output shaft is connected.

[0029] The gear section of the stepped planetary gear, whose pitch circle diameter is smaller, can engage with the other shaft of the planetary gear.

[0030] The stepped planetary gear can be rotatably mounted on a planet carrier, which is non-rotatably connected to an output shaft of the planetary gear.

[0031] The planetary gearbox, the clutch, and the electric motor can be arranged side by side in the axial direction. In this configuration, the hybrid drive system requires little installation space in the radial direction and can be designed with an aerodynamically favorable cross-sectional area.

[0032] The freewheel can be arranged either between the planetary gearbox and the transmission unit or between the transmission unit and the gas turbine engine. Arranging the freewheel between the transmission unit and the electric machine offers the advantage that, when the gas turbine engine is switched off, fewer rotating masses are in operative contact with the planetary gearbox than when the freewheel is arranged between the transmission unit and the gas turbine engine. An axial misalignment between the engine output shaft and the electric machine output shaft can be bridged in a space-saving manner perpendicular to the axial direction within the transmission unit.

[0033] In a structurally simple and cost-effective embodiment of the hybrid drive system, the transmission unit is designed as a reduction gear in spur gear construction with spur gears that mesh with each other or are connected to each other via a chain, a belt or the like.

[0034] The transmission unit can be designed as a reduction gear with a ring gear and a spur gear meshing with the ring gear. The input shaft of the transmission unit can be connected to either the spur gear or the ring gear, and the output shaft of the transmission unit can be non-rotatably connected to either the ring gear or the spur gear.

[0035] The invention is not limited to the specified combinations of features in the independent claims or the dependent claims. Furthermore, the claims provide for the possibility of combining individual features, insofar as they are apparent from the claims, the subsequent description of embodiments, or directly from the drawings. The reference in the claims to the drawings by means of reference numerals is not intended to limit the scope of protection of the claims.

[0036] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto.

[0037] It shows: Fig. 1 a highly simplified view of a first embodiment of a hybrid drive system for an aircraft with a planetary gearbox, an electric machine, a clutch, a gear unit, a gas turbine engine and a freewheel;

[0038] Fig. 2 shows a representation corresponding to Fig. 1 of another embodiment of the hybrid drive system;

[0039] Figs. 3 to 5 each show a gear diagram of different embodiments of the planetary gear of the drive system according to Fig. 1 or Fig. 2;

[0040] Fig. 6 shows a representation corresponding to Fig. 1 of a further embodiment of the hybrid drive system;

[0041] Fig. 7 shows a representation corresponding to Fig. 1 of a further embodiment of the hybrid drive system;

[0042] Fig. 8 shows a gear diagram of an embodiment of the planetary gear of the drive system according to Fig. 6 or Fig. 7;

[0043] Figs. 9 to 11 each show a gear diagram of different embodiments of the gear unit of the drive systems according to Fig. 1, Fig. 2, Fig. 6 or Fig. 7; and

[0044] Fig. 12 shows a simplified representation of an embodiment of the gas turbine engine.

[0045] Figure 1 shows a simplified representation of a hybrid propulsion system 1 for an aircraft. The hybrid propulsion system 1 comprises a gas turbine engine 2, an electric motor 3, a planetary gearbox 4, and a transmission unit 5. An engine output shaft 10 of the gas turbine engine 2 is rotatably connected to an input shaft 11 of the transmission unit 5 on the side of the gas turbine engine 2 facing the electric motor 3. An output shaft 14 of the transmission unit 5 is rotatably connected to a switching element half 15 of a freewheel 16. Another switching element half 17 of the freewheel 16 is operatively connected to a further shaft 19 extending axially X through a machine output shaft 18 of the electric motor 3. The further shaft 19 is arranged coaxially to the machine output shaft 18 of the electric machine 3 and also extends through a coupling 20 in axial direction X.The clutch 20 is designed in this case as a friction-fit switching element and can, for example, be designed as a friction-fit multi-plate clutch.

[0046] Depending on the specific application, the coupling 20 can also be designed as a hydrodynamic coupling, the filling of which can preferably be varied depending on the operating conditions. Hydrodynamic engagement can then be achieved with minimal effort and wear by changing the fill level of the coupling 20.

[0047] The electric machine 3 is designed with an external stator 21 that surrounds an internal rotor 22 in the radial direction R. The rotor 22 is non-rotatably connected to the machine output shaft 18, which is non-rotatably connected to a first switching element half 23 of the clutch 20. When the clutch 20 is appropriately actuated, the first switching element half 23 engages frictionally with a second switching element half 24 of the clutch 20 and is non-rotatably connected to it when the appropriate contact pressure is applied. The second switching element half 24 is fixedly connected to the further shaft 19, which is an input shaft of the planetary gear set 4. Fig. 2 shows another embodiment of the hybrid drive system 1, which essentially corresponds to the design of the drive system 1 according to Fig. 1. The essential difference between the drive systems 1 according to Fig. 1 and according to Fig. 2 is...The advantage of Figure 2 lies in the fact that the freewheel 16 in the drive train of the drive system 1 according to Fig. 2 is arranged between the engine output shaft 10 and the input shaft 11 of the transmission unit 5. Regarding the basic design of the drive system 1 according to Fig. 2, reference is made to the preceding description of Fig. 1.

[0048] The positioning of the freewheel 16 between the gearbox unit 5 and the electric machine 3 offers the advantage, compared to the arrangement between the gearbox unit 5 and the gas turbine engine 2, that the number of rotating masses that are connected to the planetary gearbox 4 in the event of the gas turbine engine 2 being switched off or defective is lower.

[0049] Figures 3 to 5 each show a gear diagram of various possible configurations of the planetary gear set 4. The planetary gear set 4 according to Figure 3 is designed as a stepped planetary gear set. The further shaft 19 is non-rotatably connected to a rotatable shaft 25 of the planetary gear set 4, which is designed as a sun gear. The sun gear 25 meshes with first tooth sections 26 of stepped planetary gears 27 of the planetary gear set 4, the second tooth sections 28 of which each mesh with a ring gear 29 fixed to the housing.

[0050] The pitch circle diameters of the first gear sections 26 are each larger than the pitch circle diameters of the second gear sections 28 of the stepped planetary gears 27. The stepped planetary gears 27 are rotatably mounted on a planet carrier 30, which is fixedly connected to an output shaft 31 of the planetary gear set 4. The output shaft 31 can, for example, be connected to a propeller or a fan of an aircraft engine equipped with the hybrid drive system 1. Depending on the specific application, it is also possible for the pitch circle diameters of the first gear sections 26 to be smaller than the pitch circle diameters of the second gear sections 28 of the stepped planetary gears 27. By adjusting the pitch circle diameters of the gear sections 26 and 28, it is possible to control the gear ratio.The reduction ratio of the planetary gear 4 is to be adjusted so that the electric machine 3 can be operated in an efficiency-optimal speed range.

[0051] Fig. 4 shows the planetary gear set 4, which is designed as a so-called simple planetary gear set with a ring gear 32, a planet carrier 33, at least three planet gears 34, and a sun gear 35. The sun gear 35 is connected to the further shaft 19 and meshes with the planet gear 34, which engages with the non-rotatably designed ring gear 32 and is rotatably mounted on the planet carrier 33. The planet carrier 33 is non-rotatably connected to the output shaft 31 of the planetary gear set 4.

[0052] A gear diagram of another embodiment of the planetary gear set 4 is shown in Fig. 5. The planetary gear set 4 has two simple planet gear sets 36, 37, each comprising a sun gear 38 or 39, a planet carrier 40 or 41, a ring gear 42 or 43, and planet gears 44 or 45. The further shaft 19 is non-rotatably connected to the planet carrier 40 of planet gear set 36 and to the planet carrier 41 of planet gear set 37. The sun gear 38 of planet gear set 36 is non-rotatably coupled to the rotatable ring gear 43 of planet gear set 37, while the sun gear 39 of planet gear set 37 is connected to the output shaft 31 of the planetary gear set 4. The planet gear 44 of the planet gear set 36 meshes with the sun gear 38 and the rotationally fixed ring gear 42 of the planet gear set 36.

[0053] Figures 6 and 7 show corresponding representations of two further embodiments of the hybrid drive system 1, corresponding to Figures 1 and 2 respectively. These embodiments differ from the drive systems 1 according to Figures 1 and 2 only in certain aspects. Therefore, the following description will focus primarily on the differences between the hybrid drive systems 1 according to Figures 6 and 7 and the hybrid drive systems 1 according to Figures 1 and 2. For the basic operating principle and fundamental design of the hybrid drive systems 1 according to Figures 6 and 7, reference is made to the preceding description.

[0054] In the hybrid drive system 1 according to Fig. 6, the freewheel 16 is arranged in the axial direction X between the electric machine 3 and the gearbox unit 5, as in the drive system 1 according to Fig. 1. In contrast, in the drive system 1 according to Fig. 7, the freewheel 16 is positioned between the gas turbine engine 2 and the gearbox unit 5, as in the drive system 1 according to Fig. 2.

[0055] The switching element half 15 of the freewheel 16 of the drive system 1 according to Fig. 6 is rotationally fixed to the output shaft 14 of the gear unit 5, while the other switching element half 17 of the freewheel 16 is rotationally fixed to the other shaft 19. In the drive system 1 according to Fig. 7, the switching element half 15 of the freewheel 16 is rotationally fixed to the engine output shaft 10 and the other switching element half 17 of the freewheel 16 is rotationally fixed to the input shaft 11 of the gear unit 5.

[0056] The output shaft 14 of the gear unit 5 of the drive system 1 according to Fig. 7 passes through the machine output shaft 18 in the axial direction X in the same manner as the further shaft 19 of the hybrid drive system 1 according to Fig. 6. The output shaft 14 and the further shaft 19 of the drive systems 1 according to Fig. 6 and Fig. 7 respectively each represent an input shaft of the planetary gear 4.

[0057] The motor output shaft 18 is non-rotatably connected to the first switching element half 23 of the clutch 20 and can be non-rotatably connected to the further or second switching element half 24 of the clutch 20 in the manner described above. The second switching element half 24 is non-rotatably connected to a second input shaft 63 of the planetary gear 4.

[0058] Fig. 8 shows a gear diagram of a possible embodiment of the planetary gear set 4, which is designed as a stepped planetary gear set. The second switching element half 24 of the clutch 20 is non-rotatably connected to a second sun gear or a second shaft 63 of the planetary gear set 4. The second sun gear meshes with second tooth sections 48 of stepped planetary gear sets 47, the pitch circle diameters of which are smaller than the pitch circle diameters of first tooth sections 46 of the stepped planetary gear sets 47. Additionally, the second tooth sections 48 mesh with a non-rotatably connected ring gear 49. The first tooth section 46, in turn, meshes with a first sun gear 56. A planet carrier 50, on which the stepped planetary gear sets 47 are rotatably mounted, drives the output shaft 31 of the planetary gear set 4.

[0059] Depending on the specific application, it is also possible that the pitch circle diameters of the first gear sections 46 are smaller than the pitch circle diameters of the second gear sections 48 of the stepped planetary gears 47. By designing the pitch circle diameters of the gear sections 46 and 48, it is possible to adjust the gear ratio or reduction of the planetary gear set 4 so that the electric machine 3 can be operated in an efficiency-optimized speed range, depending on its design.

[0060] In the various embodiments of the hybrid drive system 1 described above, the electric machine 3 and the gas turbine engine 2 are radially offset from each other in the direction R and axially arranged side by side. Any axial misalignment between the engine output shaft 10 and the machine output shaft 18 is compensated for or bridged in the area of ​​the gearbox unit 5. Since the gas turbine engine 2 and the electric machine 3 are arranged side by side in the axial direction X, only the planetary gearbox 4 needs to be designed for the total power output of the hybrid drive system 1, allowing the remaining components of the drive system 1 to be designed with lower component strengths. This enables the drive system 1 to be designed with a low component weight.

[0061] Furthermore, in the design of the planetary gear 4 as a stepped planetary gear according to Fig. 8, the power of the electric machine 3 is transmitted partly by the toothing area 46 and partly by the toothing area 48 of the stepped planetary gears 47 50, whereby the majority of the planetary gear 4 is subjected to only low loads during operation.

[0062] Figures 9 to 11 each show a gear diagram of various possible configurations of the gear unit 5, which is designed as a reduction gear, wherein the gear unit 5 according to Figure 9 is a spur gear transmission. A spur gear 51 is fixedly mounted on the input shaft 11 of the gear unit 5 according to Figure 9, which meshes with another spur gear 52 of the gear unit 5. The other spur gear 52 is fixedly mounted on the output shaft 14 of the gear unit 5.

[0063] To bridge larger radial distances R between the input shaft 11 and the output shaft 14 of the transmission unit 5, the input shaft 11 and the output shaft 14 of the transmission unit 5 are connected to each other via a chain 53 or a belt 54, depending on the specific application, as shown in Fig. 10. These belts or belts 51A, 52A, or pulleys 51B, 52B of the transmission unit 5 as shown in Fig. 10, which are rotationally fixed to the input shaft 11 and the output shaft 14, respectively. Furthermore, the transmission unit 5 can also have a ring gear 55, as shown in Fig. 11, into which a spur gear 57 engages. In this configuration, the spur gear 57 can be rotationally fixed to the input shaft 11 and the ring gear 55 to the output shaft 14.

[0064] Figure 12 shows a possible embodiment of the gas turbine engine 2, which comprises a low-pressure compressor 58 and a high-pressure compressor 59, which are connected to a high-pressure turbine 61 via a coupling shaft 60. A low-pressure turbine 62 is connected axially to the high-pressure turbine 61 in the X direction and drives the engine output shaft 10 of the gas turbine engine 2.

[0065] It should be noted that the illustrated design of the gas turbine engine 2 is merely exemplary and that the gas turbine engine 2 may be designed in a different way at the discretion of the person skilled in the art and depending on the specific application, in order to provide a corresponding drive torque in a cost-effective and space-saving manner with low energy consumption.

[0066] In principle, all the hybrid drive systems 1 described above offer the possibility of driving the output shaft 31 of the planetary gearbox 4 from both the gas turbine engine 2 and the motor-driven electric machine 3 when high drive torque is required. Parallel drive of the output shaft 31 is possible when the rotational speed of the switching element half 15 of the freewheel 16 is greater than the rotational speed of the other switching element half 17 of the freewheel 16 and the clutch 20 is also engaged. High drive torques and the resulting high thrust are required, for example, during climbs or takeoffs of an aircraft. The electric machine 3 can be supplied with electrical energy for this purpose by an electrical energy storage device and / or a fuel cell.In contrast, during flight operating conditions with lower power requirements, such as level flight, a lower drive torque is needed. In such cases, it may be sufficient to drive the output shaft 31 solely from the gas turbine engine 2. The coupling 20 can then be opened, for example, and the electric machine 3 decoupled from the drive train of the propulsion system 1. This allows the gas turbine engine 2 to be designed with lower power output, and therefore with smaller external dimensions and lower component weight, compared to conventional gas turbine engines without an additional electric machine.

[0067] If, however, the rotational speed of the switching element half 15 of the freewheel 16 is lower than the rotational speed of the other switching element half 17 of the freewheel 16, the connection between the two switching element halves 15 and 17 of the freewheel 16 disengages automatically. Then, no torque is transmitted via the freewheel 16 from the engine output shaft 10 of the gas turbine engine 2 towards the planetary gear 4. During such an operating state of the hybrid drive system 1, it is possible to drive the output shaft 31 with the clutch 20 engaged only via the then motor-driven electric machine 3.

[0068] If the electric machine 3 can also be operated in generator mode, it is possible to drive the electric machine 3 in a torque-transmitting operating state of the coupling 20 with a portion of the drive torque of the gas turbine engine 2, while the other portion of the drive torque of the gas turbine engine 2 is used to generate thrust. The generator-operated electric machine 3 can then produce electrical energy, which can be used, for example, to charge an electrical energy storage device or the generated energy can be used for electrolysis to produce hydrogen for a fuel cell. The stored energy can then be fed into the vehicle's electrical system as needed.Regardless of the specific design of the coupling 20, it is advantageously configured to transmit both a drive torque from the motor-driven electric machine 3 towards the planetary gear 4 and a drive torque from the gas turbine engine 2 towards the electric machine 3 when the latter is operating in generator mode. Furthermore, the coupling 20 is designed to transmit torque peaks occurring during operation without high differential speeds. This prevents excessively high operating temperatures and undesirably high wear in the area of ​​the coupling 20.

[0069] Furthermore, the coupling 20 is designed such that it switches to the open operating state in the event of a fault. This ensures, in the event of a fault, that the operation of the drive system 1 is not affected by a permanently connected electric machine 3.

[0070] In addition, torque fluctuations occurring during the operation of the drive system 1, i.e. shock loads, are dampened in the area of ​​the clutch 20, since the clutch 20 then briefly enters a slipping operating state due to its design.

[0071] To avoid excessive stress on the clutch 20, a speed difference between the switching element halves 23 and 24 can be controlled by a corresponding motor operation of the electric machine 3, moving it towards a defined differential speed window. Within this defined differential speed window, the clutch 20 can be transitioned to a slip-free closed operating state or a low-slip operating state with short slip phases and without causing undesirable torque surges. (See also: List of symbols for hybrid drive system)

[0072] Gas turbine engine, electric machine, planetary gearbox

[0073] Gear unit

[0074] Engine output shaft

[0075] Input shaft of the gearbox unit

[0076] Output shaft of the gearbox unit

[0077] Switching element half of the freewheel

[0078] Freewheel, further switching element half of the freewheel

[0079] Machine output shaft, further shaft

[0080] coupling

[0081] Stator, internal rotor, first half of the coupling's switching element, second half of the coupling's switching element, shaft, sun gear, first toothed section of the stepped planetary gear, stepped planetary gear, second toothed section of the stepped planetary gear, ring gear

[0082] Planetary carrier

[0083] Output shaft of the planetary gear

[0084] ring gear

[0085] Planetary carrier

[0086] planet gear

[0087] Sun gear, simple planetary gear set, simple planetary gear set

[0088] Sun gear of the simple planetary gear set 36

[0089] Sun gear of the simple planetary gear set 37

[0090] Planet carrier of the simple planetary gear set 36

[0091] Planet carrier of the simple planetary gear set 37

[0092] Ring gear of the simple planetary gear set 36

[0093] Ring gear of the simple planetary gear set 37

[0094] Planet gear of the simple planet gear set 36

[0095] Planet gear of the simple planetary gear set 37 first toothing area of ​​the stepped planetary gear 47

[0096] Stepped planetary gear, second toothing area of ​​the stepped planetary gear 47

[0097] ring gear

[0098] Planetary carrier

[0099] Spur gear A, gear B, disc; further spur gear A, gear B, disc

[0100] Chain

[0101] belt

[0102] Ring gear, first shaft or sun gear

[0103] Spur gear

[0104] Low-pressure compressor

[0105] High-pressure compressor

[0106] coupling shaft

[0107] High-pressure turbine

[0108] Low-pressure turbine 63 second sun wheel

[0109] R radial direction

[0110] X axial direction

Claims

Patent claims 1. A hybrid propulsion system (1) for an aircraft comprising a gas turbine engine (2) configured to drive an engine output shaft (10) which can be connected to a planetary gear (4) via a freewheel (16), an electric machine (3) configured to drive a machine output shaft (18) which can be operatively connected to the planetary gear (4) via a coupling (20), and a transmission unit (5) with an input shaft (11) and with an output shaft (14), wherein the input shaft (11) is offset from the output shaft (14) and coaxial with the engine output shaft (10), and wherein either the input shaft (11) can be connected to the engine output shaft (10) via the freewheel (16) and the output shaft (14), which is arranged coaxially with the machine output shaft (18), is connected to the planetary gear (4). is, or the output shaft (14) via the freewheel (16) with another shaft (19),which runs coaxially to the machine output shaft (18), can be connected to the planetary gear (4) and the input shaft (11) is connected to the engine output shaft (10).

2. Hybrid drive system according to claim 1, characterized in that the output shaft (14) and the further shaft (19) are coaxial to each other.

3. Hybrid drive system according to claim 1 or 2, characterized in that the further shaft (19) or the output shaft (14) extends through the machine output shaft (18) in axial direction (X) from the gear unit (5A) in the direction of the planetary gear (4).

4. Hybrid drive system according to one of the preceding claims, characterized in that the further shaft (19) or the output shaft (14) is connected to a first switching element half (23) of the clutch (20), which can be engaged with a second switching element half (24) of the clutch (20), which is connected to the machine output shaft (18), whereby the machine output shaft (18) can be connected via the clutch (20) to the further shaft (19) or to the output shaft (14).

5. Hybrid drive system according to one of the preceding claims, characterized in that the further shaft (19) or the output shaft (14) is connected to a shaft (25) of the planetary gear (4) which is designed as a sun gear, ring gear or planet carrier.

6. Hybrid drive system according to one of the preceding claims, characterized in that the planetary gear (4) is designed as a simple planetary gear set, wherein a transmission ratio of the planetary gear (4) has values ​​in a transmission range of 2.3:1 to 8.0:

1.

7. Hybrid drive system according to one of the preceding claims, characterized in that the planetary gear (4) consists of at least two simple planetary gear sets (36, 37) connected to each other in a back-to-back arrangement, wherein the ratios of the simple planetary gear sets (36, 37) each have values ​​in a ratio range of 2.3:1 to 8.0:

1.

8. Hybrid drive system according to one of the preceding claims, characterized in that the further shaft (19) or the output shaft (14) is connected to a rotatable first shaft (56) of the planetary gear (4), which is designed as a sun gear, ring gear or planet carrier, and a first switching element half (23) of the clutch (20) is connected to the machine output shaft (18), wherein the first switching element half (23) of the The clutch (20) can be brought into operative contact with a second switching element half (24) of the clutch (20), which is rotatably connected to a rotatable second shaft (63) of the planetary gear (4), which is designed as a sun gear, ring gear or planet carrier.

9. Hybrid drive system according to one of the preceding claims, characterized in that the planetary gear (4) is designed as a stepped planetary gear with at least one stepped planet (27; 47) having two toothed sections (26, 28; 46, 48) whose pitch circle diameters differ, wherein a first toothed section (26; 48) engages with a rotationally fixed ring gear (29; 49) of the planetary gear (4).

10. Hybrid drive system according to claim 9, characterized in that a gear ratio of the stepped planetary gear (4) has values ​​in a gear ratio range of 4.0:1 to 20:

1.

11. Hybrid drive system according to claim 9 or 10, characterized in that the second gear section (28; 48) of the stepped planetary gear (27; 47) engages with the second shaft (63) of the planetary gear (4).

12. Hybrid drive system according to one of claims 9 to 11, characterized in that a first gearing area (26; 46) of the stepped planetary gear (27; 47) engages with the first shaft (25; 56) with which the further shaft (19) or the output shaft (14) is connected.

13. Hybrid drive system according to one of claims 9 to 12, characterized in that the step planet (27; 47) is mounted on a planet carrier (30; 50) is rotatably mounted, which is non-rotatably connected to an output shaft (31) of the planetary gear (4).

14. Hybrid drive system according to one of the preceding claims, characterized in that the planetary gear (4), the clutch (20) and the electric machine (3) follow one another in the axial direction (3) and the freewheel (16) is arranged either between the electric machine (3) and the gear unit (5) or between the gear unit (5) and the gas turbine engine (2).

15. Hybrid drive system according to one of the preceding claims, characterized in that an axis offset between the engine output shaft (10) and the machine output shaft (18) perpendicular to the axial direction (X) is bridged in the area of ​​the transmission unit (5).

16. Hybrid drive system according to one of the preceding claims, characterized in that the transmission unit (5) is designed as a reduction gear in spur gear construction with spur gears (51 , 52) that mesh with each other or are connected to each other via a chain (53), a belt (54) or the like.

17. Hybrid drive system according to one of the preceding claims, characterized in that the transmission unit (5) is designed as a reduction gear with a ring gear (55) and with a spur gear (57) meshing with the ring gear (55), wherein the input shaft (11) of the transmission unit (5) is connected to the spur gear (57) or the ring gear (55) and the output shaft (14) of the transmission unit (5) is in rotationally fixed operative connection with the ring gear (55) or with the spur gear (57).

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