EP4588780A1

EP4588780A1 - Marine hybrid transmission and marine hybrid drive

Info

Publication number: EP4588780A1
Application number: EP24152872.8A
Authority: EP
Inventors: Mattia Caracristi; Michele Zottele
Original assignee: ZF Friedrichshafen AG; ZF Padova SRL
Current assignee: ZF Friedrichshafen AG; ZF Padova SRL
Priority date: 2024-01-19
Filing date: 2024-01-19
Publication date: 2025-07-23

Abstract

The present invention relates to a marine hybrid transmission (1) comprising a housing (2), a first input shaft (11), a second input shaft (21) and an output shaft (30) which is connected to a propeller shaft (40).The first input shaft (11) is connectable to a combustion engine (10) and the second input shaft (21) is connectable to an electric machine (20). The first input shaft (11) is arranged coaxially to the second input shaft (21).The marine hybrid transmission (1) further comprising a clutch assembly (25) to selectively connect a motor shaft (22) of the electric machine (20) either to the first input shaft (11) or to the second input shaft (21).The invention further relates to a marine hybrid drive (100) with such a marine hybrid transmission (1).

Description

The present invention relates to a marine hybrid transmission and to a marine hybrid drive with such a marine hybrid transmission.
Conventional marine drives comprise a combustion engine, which can be mounted inside a hull of a ship. The power from the combustion engine is transmitted via a drive train with shafts and transmission elements to one or two propellers, which are fixed to a propeller shaft. Typically a forward and a reverse clutch are arranged in the drive train, to realize forward and reverse rotation directions of the propeller shaft.
In recent years there is an increasing demand for marine drive units with electric drive machines for environmental and efficiency reasons. For these reasons several marine drive units have been proposed in form of hybrid drives comprising a combustion engine and an electric machine for driving the water vessel.
In the EP 2 396 219 A1 a hybrid marine power train with a combustion engine and an electric motor has been disclosed. A transmission input shaft can be driven by the combustion engine or by the electric motor and the drive power is transmitted from a first input shaft via a clutch to a main shaft and further to an output shaft. The electric motor can be connected to the first input shaft via a second input shaft.
The purpose of the present invention is to provide an improved marine hybrid transmission with a high level of reliability and a broad range of applicability.
This purpose is achieved by a marine hybrid transmission according to claim 1 and by a marine hybrid drive according to claim 10. Further embodiments are claimed in dependent claims.
The present invention provides a marine hybrid transmission comprising a housing, a first input shaft, a second input shaft and an output shaft which is connected to a propeller shaft.
The first input shaft is to be connected to a combustion engine and the second input shaft is to be connected to an electric machine. The first input shaft is arranged coaxially to the second input shaft. The marine hybrid transmission further comprising a clutch assembly to selectively connect a motor shaft of the electric machine either to the first input shaft or to the second input shaft. This means that the power of the electric machine can be transmitted either via the first input shaft or via the second input shaft, depending on the status of the clutch assembly.
In a first embodiment of the invention, the clutch assembly comprises a sliding bushing which is permanently connected to the motor shaft to rotate with the motor shaft. Said sliding bushing can be moved in axial direction to a first switch position A and a second switch position B. In the first switch position A the motor shaft is connected to the first input shaft and in the second switch position B the motor shaft is connected to the second input shaft. Hence, the sliding bushing can selectively connect the motor shaft either to the first input shaft or to the second input shaft. In the first switch position A and in the second switch position B power and torque can be transmitted via the sliding bushing.
Additionally there may be a third switch position C of the clutch assembly. In the third switch position C, the motor shaft is disconnected from the first input shaft and from the second input shaft, so that in the third switch position C no power will be transmitted via the sliding bushing and consequently no power can be transmitted from the electric machine to the first or to the second input shaft or vice versa. Such disconnection of the electric machine allows a decrease of the inertia coming from the rotational masses. The third switch position C can particularly be applied in operating modes when the propulsion power for the propeller is provided solely from the combustion engine, and when the battery recharge is not needed.
Said clutch assembly generally may comprise friction clutch elements or form-fit elements. Preferably the cutch assembly includes form-fit elements, like splined connections. Form-fit clutches can easily be actuated by pneumatic or electromagnetic actuators and mean a significant simplification of the structural layout, because such form-fit clutches require less components, no oil pressure pump and no oil pressure supply components compared to oil pressure actuated friction clutches. Smooth engagement of a clutch assembly with form-fit elements can be achieved, when the rotational speeds of the respective input portion and output portion is synchronized by adapting the rotational speed, i.e. the rpm, of the motor shaft by the control of the speed of the electric machine.
In one embodiment the sliding bushing has a first inner spline which is permanently engaged with a first outer spline at the motor shaft. The sliding bushing having further a second inner spline which is engaged with a second outer spline at the first input shaft in the first switch position A. The sliding bushing further comprises a third outer spline which is engaged with a third inner spline at the second input shaft in the second switch position B. Hence, the spline connections of this embodiment are form-fit clutches. There are two form-fit clutches incorporated in such a clutch assembly. A first form-fit clutch to connect the motor shaft to the first input shaft and a second form-fit clutch to connect the motor shaft to the second input shaft. An advantage of form-fit clutches or positive-fit clutches is the compact layout compared to friction clutches. This allows for a very compact design of the proposed marine hybrid transmission.
The marine hybrid transmission may comprise a first engine clutch and a second engine clutch to transmit driving power from the first input shaft to the output shaft selectively in a forward or reverse direction by engaging the first engine clutch or the second engine clutch. The driving power of the combustion engine can therefore be transmitted to the output shaft selectively in a forward or reverse direction by engaging either the first engine clutch or the second engine clutch. This is a common configuration for a marine propulsion system, which is driven by a combustion engine whose crankshaft is driven in one rotational direction only. Hence, the driving power can be transmitted via a propeller shaft to a propeller and effect the propulsion of the water vessel in a forward or reverse direction. Engaging the first engine clutch may effect a rotation of the output shaft in a forward direction and an engagement of the second engine clutch may effect a rotation of the output shaft in a reverse direction, when the first input shaft is driven by the combustion engine. However, the rotating directions can also be related vice versa.
In embodiments for pod-drives or z-drives the output shaft is a vertical shaft, which can be connected to the first input shaft via an upper bevel gear set and to the propeller shaft by a lower bevel gear set. The upper bevel gear set of such an embodiment may comprise a first bevel pinion, a second bevel pinion and a crown gear, wherein the first and second bevel pinions are permanently meshing with the crown gear. The first bevel pinion is connectable to the first input shaft by the first engine clutch and the second bevel pinion is connectable to the first input shaft by the second engine clutch. The crown gear is fastened to the output shaft and the output shaft is connected the propeller shaft by said lower bevel gear set.
In one embodiment the second input shaft is rigidly connected to the second bevel pinion. In other words, the driving power from the electric machine can be transmitted directly from the second input shaft via the second bevel pinion and the crown gear to the output shaft. There is no power flow through one of first or second engine clutch required, when the marine hybrid drive is driven electrically, i.e. solely by the electric machine. For example in case of a failure in the pressure supply to such the pressure actuated first and second engine clutch, the power from the combustion engine via the first input shaft cannot be transmitted to the output shaft. The present invention enables to drive the output shaft in such a situation solely by the electric machine via the second input shaft. This way, the electric machine provides for a backup solution in case of failure or lack of the main propulsion from the combustion engine or a failure of the clutch. Hence, the reliability of the marine hybrid transmission and the corresponding marine hybrid drive is increased.
The electric machine alone can drive the output shaft in a forward or in a reverse direction when the first clutch and the second clutch are disengaged. This way an electric cruising is enabled, especially to cruise protected areas with low noise and zero emission. It is possible to operate the marine hybrid drive in an Eco-mode, wherein the combustion engine only runs when power requirements exceed the renewable sources and available battery capacity.
A particular compact design can be achieved in an embodiment, wherein one end of the first input shaft is supported inside the second input shaft. For this, a first end of the input shaft can be supported in the housing by a first bearing. Any kind of an engine connection is arranged at a first end of the first input shaft. Said engine connection can be a flanged connection, a splined connection, or a coupling, just to name a few examples. At the second end of the first input shaft a second bearing is arranged to support the first input shaft inside the second input shaft. The second input shaft for its part can be supported in the housing by a third bearing. There might be additional drive train components arranged between a crankshaft of the combustion engine and the first input shaft, like a flywheel, an elastic coupling, a rotational damper, or another shaft.
The clutch assembly may be enclosed in an intermediate casing which is fastened to the housing. The intermediate casing comprises a flange to be fastened to the electric machine. In such an embodiment the electric machine can be supported by the intermediate casing, so that the electric machine does not require any additional support structure and can be mounted together with the rest of the marine hybrid transmission in a hull of a water vehicle.
The invention is further related to a marine hybrid drive comprising the combustion engine, the electric machine and a marine hybrid transmission as described above.
The invention will be further and more particularly described in the following, by way of example only, and with reference to the accompanying figures.

Fig. 1: shows a schematic drawing of a marine hybrid drive with a marine hybrid transmission according to the invention with a clutch assembly in a first switch position A;
Fig. 2: shows a sectional view of the marine hybrid transmission of Fig. 1 according to the invention with a clutch assembly in a second switch position B and
Fig 3: shows a schematic view of a section of a splined connection as part of the clutch assembly.

The Marine hybrid drive 100 in Fig. 1 comprises a combustion engine 10, an electric machine 20 and a marine hybrid transmission 1. The marine hybrid transmission 1 comprising a housing 2 to enclose at least partially a first input shaft 11, a second input shaft 21 and an output shaft 30. The first input shaft 11 is connected to a crank shaft 19 of a combustion engine 10. At a first end of the first input shaft 11 there is an engine connection 18 arranged to connect the first input shaft 11 to the crank shaft 19 of the combustion engine 10. Said engine connection can be a flanged connection, a splined connection, or a coupling.
The first input shaft 11 is arranged coaxially to the second input shaft 21. The second input shaft 21 is connected to an electric machine 20. A motor shaft 22 of the electric machine 20 runs coaxial to the first input shaft 11 and to the second input shaft 21. The electric machine 20 is installed in horizontal position in the back of the marine hybrid drive 100, i.e. on the opposite side of the marine hybrid transmission 1 with regard to the combustion engine 10.
The upper part of the marine hybrid drive 100, including the combustion engine 10, the marine hybrid transmission 1 and the electric machine 20 are positioned inside a hull 101 of a corresponding water vessel. The output shaft 30 runs in a vertical direction and transmits the driving power from an upper bevel gear set 36 to a lower bevel gear set 41, which is located inside a POD beneath the hull 101. The output shaft 30 is connected to a propeller shaft 40 via a lower bevel gear set 41. The propeller 42 is mounted to the propeller shaft 40 to propel the corresponding water vessel in the water. The vertical output shaft 30 consists of two shaft parts which are arranged coaxially to each other and rigidly connected with each other.
The marine hybrid transmission 1 further comprises a clutch assembly 25 to selectively connect a motor shaft 22 of the electric machine 20 either to the first input shaft 11 or to the second input shaft 21. The clutch assembly 25 includes a sliding bushing 26 which is permanently connected to the motor shaft 22 to rotate with the motor shaft 22. The sliding bushing 26 can be selectively moved in axial direction to one of a first switch position A, a second switch position B and a third switch position C.
Fig. 2 shows the marine hybrid transmission 1 of Fig. 1 with the electric machine 20 in a more detailed sectional view. The same components are indicated with the same referals as in Fig. 1. Fig. 2 shows the sliding bushing 26 in the second switch position B.
The essential elements of the marine hybrid transmission 1 are enclosed at least partially in the housing 2 and in an intermediate casing 28, which is arranged between the housing 2 and the electric machine 20. The clutch assembly 25 is enclosed in the intermediate casing 28 which is fastened to the housing 2. The intermediate casing 28 comprises a flange 14 to fasten the electric machine 20 to a complementary flange at the housing 2. This way, the electric machine 20 can be supported by the housing 2 and does not need a separate foundation in the hull 101.
The first input shaft 11 is supported in the housing 2 by a first bearing 3. At a second end of the first input shaft 11 there is a second bearing 4 arranged to support the first input shaft 11 inside the second input shaft 21. The second input shaft 21 is a hollow shaft. The second bearing 4 in this embodiment is a roller bearing. It is arranged between the centrally arranged first input shaft 11 and the hollow second input shaft 21. A third bearing 5 is arranged to support the second input shaft 21 in the housing 2.
The upper bevel gear set 36 transmits propulsion power from the first input shaft 11 via the vertical output shaft 30 and via a lower bevel gear set 41 to the propeller shaft 40. The upper bevel gear set 36 comprises a first bevel pinion 6, a second bevel pinion 7 and a crown gear 8. Each of the two bevel pinions 6 and 7 is permanently meshing with the crown gear 8. Both bevel pinions 6 and 7 are arranged coaxial to the first input shaft 11. The first bevel pinion 6 can be drivingly connected to the first input shaft 11 by a first engine clutch 12 and the second bevel pinion 7 can be connected to the first input shaft 11 by a second engine clutch 13. Engaging the first engine clutch 12 effects a rotation of the output shaft 30 and the propeller shaft 40 in a forward direction and an engagement of the second engine clutch 13 effects a rotation of the output shaft 30 and the propeller shaft 40 in a reverse direction. Both engine clutches 12 and 13 are multi-disc friction clutches. The crown gear 8 is fastened to the vertical output shaft 30. The output shaft 30 is connected to the propeller shaft 40 by the lower bevel gear set 41. The second input shaft 21 is rigidly connected to the second bevel pinion 7, so that there is a permanent connection between the second input shaft 21 and the propeller shaft 40. Said connection between the second input shaft 21 and the propeller shaft 40 allows for forward and reverse maneuvers without any interaction with the first and second engine clutch 12 and 13 in an electric operating mode which is further described in the following.
The clutch assembly 25 is enclosed in the intermediate casing 28. The clutch assembly 25 comprising a sliding bushing 26 which is permanently connected to the motor shaft 22 of the electric machine 20 to rotate with the motor shaft 22. This permanent connection is achieved by a first inner spline 31 at the sliding bushing 26, which is permanently engaged with a corresponding first outer spline 24 at the motor shaft 22. The sliding bushing 26 is movable in axial direction. The axial direction regards to the rotation axis of the motor shaft 22. An actuation plate 27 is mounted to the sliding bushing 26 via an actuator bearing 29. The actuation plate 27 can be moved in axial direction by actuator 23 to move the sliding bushing 26 in one of the above-mentioned switch positions A, B or C. The actuator 23 can be a actuated by fluid pressure or electromagnetically.
The sliding bushing 26 comprises the first inner spline 31 which is permanently engaged with a corresponding first outer spline 24 at the motor shaft 22. The sliding bushing 26 has a second inner spline 32 at its opposite end which is engaged with a second outer spline 34 at the first input shaft 11 in the first switch position A.
The sliding bushing 26 has a third outer spline 33 which is engaged with a third inner spline 35 at the second input shaft 21 in the second switch position B, as shown in Fig. 2. In switch position B the second inner spline 32 and the second outer spline 34 are disengaged, due to the axial offset of the sliding bushing 26.
In the first switch position A the motor shaft 22 is connected to the first input shaft 11 and in the second switch position B the motor shaft 22 is connected to the second input shaft 21. In the third switch position C, the motor shaft 22 is disconnected from the first input shaft 11 and from the second input shaft 21. Therefore the third switch position C is called a neutral position. Fig. 1 shows the sliding bushing 26 in the first switch position A, whereas Fig. 2 shows the sliding bushing 26 in the second switch position B.
With the sliding bushing 26 in switch position A, the crank shaft 19 of combustion engine 10 is connected to the motor shaft 22 of electric machine 20, independent of the status of the engine clutches 12 and 13. Hence, the electric machine 20 can be used as an electric generator which is driven by the combustion engine 10, when the sliding bushing 26 is in the first switch position A. When the engine clutches 12 and 13 are both disengaged at the same time, it is possible to generate electric energy without driving the propeller 42. This way it is possible, to recharge batteries without rotations of the propeller 42.
With the sliding bushing 26 in switch position B, the crank shaft 19 of combustion engine 10 is disconnected from the motor shaft 22 of electric machine 20 and the marine drive 100 can be driven in an electric operating mode solely by the electric machine 20. In such an electric operating mode the crank shaft 19 of combustion engine 10 is disconnected from the output shaft 30 by disconnecting both engine clutches 12 and 13. In this electric operating mode, the electric machine 20 can be used to maneuver the corresponding water vessel forward and revers without any interaction of the combustion engine 10. The electric machine 20 will just rotate the two bevel pinions 6, 7 and the crown gear 8 with the output shaft 30 in the desired forward or reverse direction. A control system of the electric machine 20 can insofar be independent from a control system of the combustion engine 10.
The schematic drawing in Fig. 3 shows a section of the clutch assembly 25 with some particulars of the second inner spline 32 and the second outer spline 34. The second inner spline 32 is part of the sliding bushing 26 and the second outer spline 34 is part of the first input shaft 11. In Fig. 3 these two splines 32 and 34 are shown in a disengaged state in switch position C. These two splines 32 and 34 can be engaged with each other to achieve the first switch position A. Both splines 32 and 34 comprise a plurality of teeth which have tapered ends in order to enhance the smooth engagement of the splines during the engagement procedure. Alternatively or additionally the end of the teeth of both splines may have a complimentary frusto-conical shape to further enhance a smooth engagement. The same particulars can be also part of the third inner spline 33 and the third outer spline 35.

Referals

1: marine hybrid transmission
2: housing
3: first bearing
4: second bearing
5: third bearing
6: first bevel pinion
7: second bevel pinion
8: crown gear
10: combustion engine
11: first input shaft
12: first engine clutch
13: second engine clutch
14: flange
18: engine connection
19: crank shaft
20: electric machine
21: second input shaft
22: motor shaft
23: actuator
24: first outer spline
25: clutch assembly
26: sliding bushing
27: actuation plate
28: intermediate casing
29: actuator bearing
30: output shaft
31: first inner spline
32: second inner spline
33: third outer spline
34: second outer spline
35: third inner spline
36: upper bevel gear set
40: propeller shaft
41: lower bevel gear set
42: propeller
43: bevel gear
100: marine hybrid drive
101: hull

Claims

Marine hybrid transmission (1) comprising a housing (2), a first input shaft (11), a second input shaft (21) and an output shaft (30) which is connected to a propeller shaft (40),
wherein the first input shaft (11) is connectable to a combustion engine (10), wherein the second input shaft (21) is connectable to an electric machine (20), wherein the first input shaft (11) is arranged coaxially to the second input shaft (21),

and wherein the marine hybrid transmission (1) further comprising a clutch assembly (25) to selectively connect a motor shaft (22) of the electric machine (20) either to the first input shaft (11) or to the second input shaft (21).
Marine hybrid transmission (1) according to claim 1, wherein the clutch assembly (25) comprises a sliding bushing (26) which is permanently connected to the motor shaft (22) to rotate with the motor shaft (22), and wherein the sliding bushing (26) can be moved in axial direction to a first switch position (A) and a second switch position (B), wherein the motor shaft (22) is connected to the first input shaft (11) in the first switch position (A), and wherein the motor shaft (22) is connected to the second input shaft (21) in the second switch position (B).
Marine hybrid transmission (1) according to claim 2, wherein the sliding bushing (26) has a first inner spline (31) which is permanently engaged with a first outer spline (24) at the motor shaft (22), wherein the sliding bushing (26) has a second inner spline (32) which is engaged with a second outer spline (34) at the first input shaft (11) in the first switch position (A), and wherein the sliding bushing (26) has a third outer spline (33) which is engaged with an third inner spline (35) at the second input shaft (21) in the second switch position (B).
Marine hybrid transmission (1) according to claim 2 or 3, wherein the sliding bushing (26) can be moved to a third switch position (C), wherein the motor shaft (22) is disconnected from the first input shaft (11) and the second input shaft (21) in the third switch position (C).
Marine hybrid transmission (1) according to one of the preceding claims, comprising a first engine clutch (12) and a second engine clutch (13) to transmit driving power from the first input shaft (11) to the output shaft (30) selectively in a forward or reverse direction by engaging the first engine clutch (12) or the second engine clutch (13).
Marine hybrid transmission (1) according to claim 5, comprising an upper bevel gear set (36) with a first bevel pinion (6), a second bevel pinion (7) and a crown gear (8), wherein the first and second bevel pinion (6, 7) are permanently meshing with the crown gear (8), wherein the first bevel pinion (6) is connectable to the first input shaft (11) by the first engine clutch (12), wherein and the second bevel pinion (7) is connectable to the first input shaft (11) by the second engine clutch (13), wherein the crown gear (8) is fastened to the output shaft (30), and wherein the output shaft (30) is connected to a propeller shaft (40) by a lower bevel gear set (41).
Marine hybrid transmission (1) according to claim 6, wherein the second input shaft (21) is rigidly connected to the second bevel pinion (7).
Marine hybrid transmission (1) according to one of the preceding claims, wherein the first input shaft (11) is supported in the housing (2) by a first bearing (3), wherein an engine connection (18) is arranged at a first end of the first input shaft (11), wherein a second bearing (4) is arranged at a second end of the first input shaft (11) to support the first input shaft (11) inside the second input shaft (21), and wherein a third bearing (5) is arranged to support the second input shaft (21) in the housing (2).
Marine hybrid transmission (1) according to one of the preceding claims, wherein the clutch assembly (25) is enclosed in an intermediate casing (28) which is fastened to the housing (2), and wherein the intermediate casing (28) comprises a flange (14) to fasten the electric machine (20) to the housing (2).
Marine hybrid drive (100) comprising a combustion engine (10), an electric machine (20) and a marine hybrid transmission (1) according to one of the preceding claims.