EP4610160A1

EP4610160A1 - Hybrid pod drive

Info

Publication number: EP4610160A1
Application number: EP24160936.1A
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: 2024-03-01
Filing date: 2024-03-01
Publication date: 2025-09-03

Abstract

Hybrid pod drive (1, 102) comprising a combustion engine (2) with a crank shaft (3) which is connected to a drive shaft (4), an upper transmission unit (5) to transmit the power from the drive shaft (4) to a vertical shaft (6), a lower transmission unit (7) to transmit the power from the vertical shaft (6) to a horizontal propeller shaft (8). The hybrid pod drive (1, 102) further comprising a first electric machine (10) with a first rotor shaft (11) and a second electric machine (20) with a second rotor shaft (21). The first rotor shaft (11) is arranged coaxial to the propeller shaft (8) and the first rotor shaft (11) is permanently connected to the propeller shaft (8). The second rotor shaft (21) is permanently connected to the drive shaft (4).

Description

The present invention relates to a hybrid pod drive for marine applications with a combustion engine and with a first and a second electric machine.
In recent years there is an increasing demand for marine drive units with electric machines for environmental and efficiency reasons. For these reasons several marine drive units have been proposed in form of purely electric drives or hybrid drives. In the WO 2017/125210 A1 a hybrid propulsion device for a sailing craft has been disclosed, wherein a combustion engine is arranged in a hull and connected to a propeller shaft via a vertical shaft and a bevel gear unit. The propeller shaft is supported in an underwater housing of the hybrid propulsion device. An electric machine is arranged between the propeller shaft and a propeller inside the underwater housing.
The purpose of the present invention is to provide an improved hybrid pod drive with compact and streamlined dimensions and a high level of reliability. The hybrid pod drive shall further have a wide range of applicability.
These purposes are achieved by a hybrid pod drive according to claim 1. Further embodiments are claimed in dependent claims.
The present invention provides a hybrid pod drive comprising a combustion engine with a crank shaft, a first electric machine with a first rotor shaft and a second electric machine with a second rotor shaft. The combustion engine may be arranged inside a hull of a ship with a horizontal alignment, i.e. with horizontal crank shaft. The crank shaft of the combustion machine is connected to a drive shaft. The connection between the crank shaft of the combustion engine and the drive shaft can include an engine coupling. Such an engine coupling may comprise at least one elastic element to compensate for radial, axial, or angular offset and to provide for a damping effect.
The driving power of the combustion engine is transmitted from the drive shaft to a vertical shaft by an upper transmission unit. A lower transmission unit transmits the power from the vertical shaft to a horizontal propeller shaft which is supported in a pod housing. Each of the upper and the lower transmission units can comprise a bevel gear set. The terms horizontal and vertical refer to a hybrid pod drive mounted in an operating position on a water vessel in calm water, with the water surface being a horizontal plane and the pod is arranged underneath a hull of said water vessel. However, the terms horizontal and vertical do not limit the corresponding direction to an exact direction but include deviations from an exact horizontal or vertical direction up to an angle of 15 degrees.
The first electric machine, i.e. the first rotor shaft is permanently connected to the propeller shaft and arranged coaxial to the propeller shaft. The first rotor shaft of the first electric machine can be rigidly connected to or made in one piece with the propeller shaft. The first electric machine can be operated predominantly as an electric motor to drive the propeller shaft, whereas the second electric machine can be operated predominantly as a generator to generate electric energy. The generated electric energy can be supplied to the first electric machine to drive the propeller shaft, or it can be used to charge a battery on board of the corresponding water vessel.
The second rotor shaft, i.e. the rotor of the second electric machine is permanently connected to the drive shaft. The permanent connection of the drive shaft with the second electric machine enables the recharging of batteries by operating the combustion engine to drive the second electric machine in a generator mode, while the propeller is not rotating, when a clutch connection in the upper transmission unit is disengaged as explained further below. This way the unit can work like a so-called Genset recharging a battery from the combustion engine power without a propeller rotation. Preferably the crank shaft of the combustion engine, the drive shaft and the second rotor shaft are all arranged coaxial to each other. The combustion engine and the second electric machine can be installed on opposite sides of the upper transmission unit.
The first electric machine can preferably be arranged inside the pod housing. This means that the first electric machine is enclosed by the pod housing. A stator of the first electric machine can be rigidly fixed with regard to the pod housing. In such an embodiment the combustion engine and the second electric machine are preferably located inside a hull of the water vessel, whereas the first electric machine is arranged inside the pod housing underneath the bottom of the hull. Hence, the pod housing is positioned inside the water and the pod housing can be sealed to provide a watertight housing to protect the first electric machine and other components inside the pod housing from any detrimental influences by the ambient water. On the other side the ambient water has a cooling effect on the first electric machine inside the pod housing, so that a cooling system for the first electric machine is not necessary.
According to one embodiment a propeller is fixed to the propeller shaft, so that the propeller is mounted at a front end of the pod housing. In other words the propeller is a pulling propeller which is advantageous in view of low drag and a high efficiency during propulsion in the water. The design of the pod housing may be streamlined and optimized to a hydrodynamic shape specifically for the application with a pulling propeller. The specific design allows to install the first electric machine in a horizontal position in the back of the pod housing.
The first rotor shaft, i.e. the rotor shaft of the first electric machine can be connected to the propeller shaft via a speed reduction gear. Preferably, such a speed reduction gear is a planetary gear set, which allows for compact design and a relatively high reduction ratio. The planetary gear set can be installed between the first electric machine and the propeller shaft. By this, a speed reduction and an optimal torque and rotation speed at the propeller can be obtained when the first electric machine is used as an electric motor to drive the propeller. During the operation of the first electric machine in a generator mode, i.e. during hydrogeneration in a saildrive application, the speed reduction gear works like a speed multiplier to optimize the electric generation.
In one embodiment the upper transmission unit comprises a forward clutch and a reverse clutch to allow operation of the hybrid pod drive in forward direction, reverse direction and in a neutral status. In neutral status both clutches are disengaged. Said clutches can be arranged in the upper transmission unit together with an upper bevel gear unit, as known from conventional hybrid pod drives. However, a forward and reverse propulsion selectively can also be effected in the neutral status of the clutches when the propeller is driven solely by the power of the first electric machine. The rotating direction of the first rotor shaft and the propeller shaft can be easily switched from forward to reverse by controlling the electric supply to the first electric machine.
The pod housing may preferably comprise at least one cable duct for an electric supply cable of the first electric machine. Such a cable duct inside the pod housing provides a reliable and safe transmission of electric energy from the components inside the hull to the first electric machine in the pod housing and vice versa. No additional or separate cable ducts are necessary to be provided and installed.
The proposed hybrid pod drive may comprise a first motor control unit for the control of the first electric machine and a second motor control unit for the control of the second electric machine. The first and the second electric machines can be of different size and power rating. For example, a smaller first electric machine inside the pod housing allows for a very compact and streamlined design of the pod, what increases the hydrodynamic efficiency of the hybrid pod drive.
Further aspects of the invention belong to different operating modes of the proposed hybrid pod drive. The hybrid pod drive can be operated in a so-called Eco-mode, wherein the combustion engine is only running, when the power requirement exceeds the renewable sources, the maximum power of the electric machines or the available battery capacity. Otherwise one or both electric machines are operated as electric motor to drive the propeller shaft in a pure electric operating mode. The solely electric propulsion by the power of the first and/or second electric machine allows cruising with low noise and zero emission. This can be necessary to be allowed to enter protected areas, where water vessels are forbidden, which are driven by a combustion engine. A drive with zero-noise and zero-pollution sometimes is required in no wake areas or for docking maneuvers in a harbor area. Another advantage of the pure electric mode is, that there is no mechanical wear in those parts of the hybrid pod drive which are not operating in this mode, which increases the service life.
In other operating phases one or both electric machines can be operated together with the combustion engine in a booster mode. The combined power of both electric machines and the combustion engine can be applied to reach a maximum power of the hybrid pod drive in a so-called double over boost mode. Both in full power and also in intermediate power output where it is possible to get the best efficiency and fuel saving of the combustion engine using the first electric machine for small accelerations or changes in speed. Consequently the emissions of the combustion engine can be reduced.
In one generation mode the hybrid pod drive is driven by the combustion engine during cruising. In this charge mode from the combustion engine, the combustion engine is used to drive the water vessel by driving the propeller shaft and at the same time the second electric machine is operated in a generator mode to generate electric energy for charging. The second electric machine can be operated in a generator mode as well.
When the hybrid pod drive is operated the neutral status, i.e. with both clutches disengaged, the power of the combustion engine can be used to generate electric energy by the second electric machine without driving the propeller shaft.
In another generation mode the hydrogeneration effect is used during sailing, when the corresponding electric machine is operating in a generator mode. The effect of hydrogeneration can be used during sailing, when at least one of the first and second electric machines are switched to a generator mode and the propeller is driven by the water streaming through the propeller area of the propeller. Hence, the propeller drives the propeller shaft and at least the first rotor shaft, this way generating electric energy which can be stored in batteries on board of the water vessel. Such an operation mode can be called a charge mode from sailing cruising.
In one embodiment the first electric machine and the second electric machine can be designed with different voltage ranges or different nominal power. This way different configurations of the hybrid pod drive can beneficially be applied and optimized for different applications in a modular system.
For an independent control of the combustion engine and the electric machines, separate control systems can be provided. There can be several control units to control the combustion engine and the electric machines of the hybrid pod drive. A separate control unit can be installed for the control of the forward clutch and the reverse clutch in the upper transmission unit. Each control unit may comprise several control devices with electric and electronic components like inverters, processors, memories for storing data and/or software, interfaces and further communication means. The independently controlled electric machines provide redundancy and a high reliability. In this regard the electric machines can be a backup solution in case of a failure or lack of the combustion engine. The control units can be connected to each other and/or to a central control system of the water vessel by means of appropriate interfaces and wired or wireless connections. An appropriate drive mode in every situation can be determined and selected by the control system, depending on command signals from one or more control heads or other HMI on the water vessel. Consequently corresponding commands for the operation of the first and second electric machines can be transmitted to the first and second motor control unit.
The proposed hybrid pod drive can be used as a saildrive for sailing boats and for other ships and water vessels. The invention will be further and more particularly described in the following, by way of example only, and with reference to the accompanying figure.

Fig. 1: shows a first embodiment of a hybrid pod drive according to the invention in a schematic drawing and
Fig. 2: shows a second embodiment of a hybrid pod drive according to the invention in a more detailed drawing.

The hybrid pod drive 1 as shown in Fig. 1 is mounted on a ship 100. The hybrid pod drive 1 comprises a combustion engine 2 with a crank shaft 3, a first electric machine 10 with a first rotor shaft 11 and a second electric machine 20 with a second rotor shaft 21. The combustion engine 2 is mounted inside a hull 101 of a ship 100 so that its crank shaft 3 is oriented horizontally. This means, that a rotation axis of the crank shaft 3 runs in a horizontal plane. The crank shaft 3 is connected to a drive shaft 4 by means of an engine coupling 14. The engine coupling 14 is built and installed to compensate for radial, axial, or angular offset and for damping torsional vibrations.
The driving power of the combustion engine 2 is further transmitted from the drive shaft 4 to a vertical shaft 6 by an upper transmission unit 5. A lower transmission unit 7 transmits the power from the vertical shaft 6 to a horizontal propeller shaft 8 which is supported in a pod housing 12. The upper and the lower transmission units 5, 7 comprise each a bevel gear set.
The upper transmission unit 5 comprises a forward clutch 15 and a reverse clutch 16 in form of multi-disc clutches. An outer disc carrier of the forward clutch 15 and outer disc carrier of the reverse clutch 16 is rigidly connected to the input shaft 4. A first inner disc carrier of the forward clutch 15 is rigidly connected to a first bevel pinion 23, while a second inner disc carrier of the reverse clutch 16 is rigidly connected to a second bevel pinion 24.
A propeller 9 is fixed to the propeller shaft 8, so that the propeller 8 is mounted at the front end of the pod housing 12. This means that the propeller 8 is acting as a pulling propeller when the water vessel 100 is moving in a forward direction. The first electric machine 10 is mounted in a horizontal position in the back of the pod housing 12.
The first rotor shaft 11, i.e. the rotor shaft of the first electric machine 10 is connected to the propeller shaft 8 via a speed reduction gear 13 which is a planetary gear set. A sun gear of the speed reduction gear 13 is permanently connected to the first rotor shaft 11. A planet carrier of the speed reduction gear 13 is permanently connected to the propeller shaft 8. These connections provide for optimum rotation speed at the propeller 9 when the first electric machine 10 is operated as an electric motor to drive the propeller 9 and for optimum rotation speed of the first rotor shaft 11 for electric generation in the first electric machine 10, when the first electric machine 10 operates in a generator mode.
The combustion engine 2 and the second electric machine 20 are mounted inside the hull 101, whereas the first electric machine 10 is mounted inside the pod housing 12 which is located underneath the bottom of the hull 101. Hence, the pod housing 12 is positioned inside the water during operation. The ambient water has a cooling effect to the pod housing 12 and to the first electric machine 10.
The first electric machine 10, i.e. the first rotor shaft 11 is permanently connected to the propeller shaft 8 and arranged coaxial to the propeller shaft 8. The first electric machine 10 of this embodiment operates predominantly as an electric motor to drive the propeller shaft 8, whereas the second electric machine 20 operates predominantly as a generator to generate electric energy to charge a battery of the water vessel 100.
The second rotor shaft 21, i.e. the rotor of the second electric machine 20 is permanently connected to the drive shaft 4. The crank shaft 3 of the combustion engine 2, the drive shaft 4 and the second rotor shaft 21 are all arranged coaxial to each other. The combustion engine 2 is mounted to the upper transmission unit 5 on the opposite side of the second electric machine 20 which allows for a very flat and slim layout of the hybrid pod drive 1 to be mounted inside a hull 101 with limited space in vertical and lateral direction.
An engine control unit 30 is provided to control the combustion engine 2. A first motor control unit 31 and a second motor control unit 32 are provided for the control of the corresponding first electric machine 10 and the second electric machine 20.
The Fig. 2 shows a second embodiment of a hybrid pod drive 102. Several components of this second embodiment of the hybrid pod drive 102 have the same design and function as the corresponding component of the first embodiment of the hybrid pod drive 1 in Fig. 1. Therefore the corresponding components in Fig. 1 and Fig. 2 have identical referal numbers.
Fig. 2 shows some details of the upper transmission unit 5. It comprises a bevel gear unit with a crown gear 24 which is meshing with a first bevel pinion 22 and with a second bevel pinion 23. Crown gear 24 is fastened to the upper end of the vertical shaft 6. The first and the second bevel pinion 22, 23 are rotatably mounted on the drive haft 4. The first bevel pinion 22 can be connected to the drive shaft 4 by engaging the forward clutch 15 and the second bevel pinion 23 can be connected to the drive shaft 4 by engaging the reverse clutch 16. The corresponding directions forward and reverse may also be exchanged in other embodiments. The vertical shaft 6 of the hybrid pod drive 102 is a two-piece-shaft, wherein the crown gear 24 is rigidly fastened to an upper part of the vertical shaft 6.
The pod housing 12 comprises a cable duct 17 to encase at least one cable 18 for the electric supply of the first electric machine 10. The at least one cable 18 connects the first electric machine 10 to a first motor control unit 31 and may be further connected to a battery. The cable duct 17 inside the pod housing 12 protects the at least one electric cable 18 from water and humidity.
For applications with higher electric power demand, a first electric machine 10 with a higher nominal power rating can be selected and implemented in the pod housing 12 by simply extending the dimensions of the pod housing 12 in axial direction without enlarging the cross-sectional area of the pod. Thus, enabling the compact and streamlined design of the pod with a high hydrodynamic efficiency of the hybrid pod drive 1, 102 for a whole range of different power rated modules of the hybrid pod drives 1, 102 in a modular system.

Referals

1: hybrid pod drive
2: combustion engine
3: crank shaft
4: drive shaft
5: upper transmission unit
6: vertical shaft
7: lower transmission unit
8: propeller shaft
9: propeller
10: first electric machine
11: first rotor shaft
12: pod housing
13: speed reduction gear
14: engine coupling
15: forward clutch
16: reverse clutch
17: cable duct
18: cable
20: second electric machine
21: second rotor shaft
22: first bevel pinion
23: second bevel pinion
24: crown gear
30: engine control unit
31: first motor control unit
32: second motor control unit

100: water vessel
101: hull
102: hybrid pod drive

Claims

Hybrid pod drive (1, 102) comprising a combustion engine (2) with a crank shaft (3) which is connected to a drive shaft (4), an upper transmission unit (5) to transmit the power from the drive shaft (4) to a vertical shaft (6), a lower transmission unit (7) to transmit the power from the vertical shaft (6) to a horizontal propeller shaft (8), a first electric machine (10) with a first rotor shaft (11) and a second electric machine (20) with a second rotor shaft (21), wherein the first rotor shaft (11) is arranged coaxial to the propeller shaft (8), wherein the first rotor shaft (11) is permanently connected to the propeller shaft (8) and wherein the second rotor shaft (21) is permanently connected to the drive shaft (4).
Hybrid pod drive (1, 102) according to claim 1, wherein the propeller shaft (8) is supported in a pod housing (12), and wherein the first electric machine (10) is arranged in the pod housing (12).
Hybrid pod drive (1, 102) according to claim 1 or 2, wherein a propeller (9) is fixed to the propeller shaft (8), so that the propeller (9) is mounted at a front end of the pod housing (12).
Hybrid pod drive (1, 102) according to one of the preceding claims, wherein the first rotor shaft (11) is connected to the propeller shaft (8) via a speed reduction gear (13).
Hybrid pod drive (1, 102) according to one of the preceding claims, wherein the upper transmission unit (5) comprises a forward clutch (15) and a reverse clutch (16).
Hybrid pod drive (1, 102) according to one of claims 2 to 5, wherein the pod housing (12) comprises at least one cable duct (17) for an electric supply cable of the first electric machine (10).
Hybrid pod drive (1, 102) according to one of the preceding claims, wherein a first motor control unit (31) is provided to control the first electric machine (10), and wherein a second motor control unit (32) is provided for the control of the second electric machine (20).