Hybrid pod drive assembly and hybrid pod drive

Abstract

A hybrid pod drive assembly (1) comprising a horizontal drive shaft (4) which can be driven by a combustion engine (2) and which is connectable to a vertical shaft (6). The hybrid pod drive assembly (1) comprising a lower transmission unit (7) to transmit the power from the vertical shaft (6) to at least a first propeller shaft (12). The hybrid pod drive assembly (1) further comprising a first electric machine (10) with a first rotor shaft (11) which is coaxial with the first propeller shaft (12) and connected to the first propeller shaft (12). The hybrid pod drive assembly (1) further comprising a second electric machine (20) with a second rotor shaft (21) which is coaxial with a second propeller shaft (22) and connected to the second propeller shaft (22). The second propeller shaft (22) is surrounding the first propeller shaft (12). A rear propeller (13) is mounted to a trailing end of the first propeller shaft (12) and a front propeller (23) is mounted to a trailing end of the second propeller shaft (22). The invention further relates to a corresponding hybrid pod drive (102).

Description

[0001] The present invention relates to a hybrid pod drive assembly for marine applications with a first and a second electric machine and a corresponding hybrid pod drive with a combustion engine.

[0002] 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 DE 10 2009 024 925 A1 a hybrid propulsion device for a commercial watercraft has been disclosed, wherein a horizontally positioned combustion engine is arranged in a hull and connected to a horizontal propeller shaft via a horizontal drive shaft, a vertical shaft, and a gear unit. The propeller shaft is supported in an underwater drive unit. Two electric motors are arranged coaxial to the propeller shaft inside the underwater drive unit.

[0003] EP 2 468 624 B1 shows a hybrid marine propulsion device comprising a main engine, a motor, a clutch provided to the input shaft of the main engine; a horizontal input / output shaft, which is connected to the clutch; a vertical shaft which is joined to the input / output shaft by means of an upper bevel gear; a horizontal propeller axis which is joined to a bottom tip of the vertical shaft by means of a lower bevel gear; and a propeller which is located on the propeller shaft on the other tip side to where the propeller shaft is joined to the vertical shaft. A motor-generator is attached on top of a base and directly connected to the other end side of the input / output shaft to where the vertical shaft is located.

[0004] The purpose of the present invention is to provide an improved hybrid pod drive assembly with compact and streamlined dimensions and a high level of reliability. The hybrid pod drive assembly shall further have a wide range of applicability. Besides, a corresponding hybrid pod drive shall be provided.

[0005] These purposes are achieved by a hybrid pod drive assembly according to claim 1 and by a hybrid pod drive according to claim 6. Further embodiments are claimed in dependent claims.

[0006] The present invention provides a hybrid pod drive assembly with a horizontal drive shaft which can be driven by a combustion engine, and which is connectable to a vertical shaft. The combustion engine may be mounted inside a hull of a water vessel in an essentially horizontal position, i.e. the rotation axis of a crank shaft runs in a horizontal direction. The term connectable means, that the connection between the drive shaft and the vertical shaft can be established by means of at least one clutch. An upper transmission unit may be installed to transmit the power of the combustion engine from the drive shaft to the vertical shaft. A lower transmission unit is installed to transmit the power from the vertical shaft to at least a first propeller shaft.

[0007] The terms horizontal and vertical refer to a hybrid pod drive mounted in an operating position on a water vessel in calm water. However, the terms horizontal and vertical do not limit the corresponding direction to an exact direction but include deviations up to an angle of 15 degrees. Hence, the terms horizontal and vertical can be understood as approximate designations.

[0008] The hybrid pod drive assembly further comprising a first electric machine with a first rotor shaft which is coaxial with the first propeller shaft and connected to the first propeller shaft. The first rotor shaft can be an integral part of a rotor of the first electric machine or rigidly connected to it. The first rotor shaft can be directly and rigidly connected to the first propeller shaft or via other components like a speed reduction gear, as further explained below.

[0009] The hybrid pod drive assembly further comprising a second electric machine with a second rotor shaft which is coaxial with a second propeller shaft and connected to the second propeller shaft. Hence, the hybrid pod drive assembly includes a first and a second propeller shaft. The second propeller shaft is surrounding the first propeller shaft. The second propeller shaft is a hollow shaft, and the first propeller shaft extends through the second propeller shaft. In other words the first propeller shaft is arranged coaxial to the second propeller shaft.

[0010] A rear propeller is mounted to a trailing end of the first propeller shaft and a front propeller is mounted to a trailing end of the second propeller shaft. Both propellers can be arranged one after the other at the trailing end of a pod respectively a pod housing. Preferably the two propellers act as counterrotating propellers. Therefore in one embodiment the lower transmission unit is arranged to transmit the power from the vertical shaft to the first propeller shaft and to the second propeller shaft in a way to rotate the first and the second propeller shafts in opposite rotational directions from one another.

[0011] In another embodiment the lower transmission unit may transmit the power from the vertical shaft only to the first propeller shaft or to the second propeller shaft, while the other propeller shaft is driven by the corresponding electric machine, only. The contrarotating effect can be realized anyway by adjusting the appropriate rotating direction of the corresponding electric machine to rotate the second propeller shaft opposite direction to the first propeller shaft.

[0012] Another aspect of the invention is the position of the first and second electric machine in the pod. The first and second electric machines can both be arranged inside a 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 two electric machines 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 electric machines inside the pod housing. Hence, no separate cooling system for the electric machines is necessary. In one embodiment the lower transmission unit between the first electric machine and the second electric machine in axial direction. In in this embodiment the first electric machine is installed in the front of the pod housing and the second electric machine is installed in the back of the pod housing. The second electric machine is fitted with a hollow second rotor shaft which is arranged on the coaxial and central first propeller shaft that is connected to the rear propeller. Such an arrangement of the components enables a streamlined and efficient hydrodynamic design of the pod. This way the hydrodynamic shape of the pod housing can be optimized to minimize the drag force during cruising, although it could increase in the dimension with respect to a conventional pod without any electric machine. The front propellor and / or the rear propeller can be a variable pitch propeller or a foldable propeller in order to further increase efficiency when the corresponding propeller is not used for propulsion.

[0013] In alternative embodiments the first rotor shaft can be connected to the first propeller shaft via a first speed reduction gear and / or the second rotor shaft can be connected to the second propeller shaft via a second speed reduction gear. Such speed reduction gears can be installed to obtain a speed reduction and have an optimal torque and rotation speed at the corresponding propeller. At the same time, if one or both propellers are used for hydrogeneration in a sail drive application the speed reduction gear can work like a speed multiplier for optimizing the electric generation. A preferred type of speed reduction gear is a planetary gear because it can be implemented with very compact dimensions in relation to a high gear ratio.

[0014] The upper transmission unit may comprise a forward clutch and a reverse clutch to transmit driving power from the combustion engine to the vertical shaft selectively in a forward or reverse direction by engaging the corresponding clutch. So the combustion engine can be used to propel the water vessel in a forward or in a reverse direction, depending on the corresponding clutch engagement. A disengagement of both clutches allows for a complete disconnection between the crank shaft of the combustion engine and the vertical shaft, this means a disconnection between the combustion engine and the propellers. The hybrid pod drive assembly can be operated solely by one or both electric machines in forward and reverse direction, when both clutches are disengaged. Both clutches can be pressure operated clutches. In case of a failure in the pressure supply to the clutches, the power from the combustion engine cannot be transmitted from the drive shaft to the vertical shaft. The present invention enables to drive the output shaft in such a situation by the first electric machine and / or the second electric machine. This way, the electric machines provide for a backup solution in case of failure or lack of the main propulsion from the combustion engine or a failure of the clutches. Hence, the reliability of such a hybrid pod drive is increased.

[0015] 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 assembly can beneficially be applied and optimized for different applications in a modular system.

[0016] The first electric machine and the second electric machine can be controlled and can work independently from each other and from the combustion engine. That means for example the rotation speed of one electric machine can be adjusted independent from the rotation speed of the other electric machine to optimize the counter rotation effect. Another example with regard energy savings is to switch off or reduce the rotation speed of the second electric machine if the power of the first electric machine is sufficient for very low speed cruising. 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 assembly. A separate control unit can be installed for the control of the forward 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.

[0017] 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 corresponding control unit.

[0018] Besides the invention relates to a hybrid pod drive including a hybrid pod drive assembly as described above and the combustion engine.

[0019] 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 only one or both electric machines are operated 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 protected areas, where water vessels are forbidden which are driven by a combustion engine. Cruising 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.

[0020] 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. Electric drive support can be used in full power and in intermediate power output, whenever it is possible to get the best efficiency and fuel saving of the combustion engine, e.g. by using the power of the first and / or the second electric machine for small accelerations or changes in speed. Consequently the emissions of the combustion engine can be reduced.

[0021] In a first generating mode the hybrid pod drive is driven by the combustion engine during cruising. In this charge mode the combustion engine is used to mechanically drive the water vessel by driving at least one of the propeller shafts and at the same time at least one of the two electric machines is operated in a generator mode to generate electric energy for charging a battery aboard the water vessel.

[0022] The proposed hybrid pod drive provides an optimal integration between the combustion engine and the two electric machines to drive the counter rotating propellers, and in addition to have the possibilities to recharge the battery from the combustion engine during the cruising.

[0023] In a second generating mode the hydrogeneration effect is used during sailing, when the corresponding electric machine is operating in a generator mode and the combustion engine is disconnected from the propeller shafts, e.g. by disengaged the above mentioned forward and the reverse clutches. 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 corresponding propeller is driven by the water streaming through the propeller area. Hence, the propeller drives the propeller shaft and the rotor shaft of the corresponding electric machine, 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.

[0024] 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. 1shows an embodiment of a hybrid pod drive according to the invention in a schematic drawing.

[0025] The hybrid pod drive 102 as shown in Fig. 1 is mounted on a ship 100. The complete hybrid pod drive 102 comprises a hybrid pod drive assembly 1 and a combustion engine 2 with a crank shaft 3. The hybrid pod drive assembly 1 excludes the combustion engine 2 with its crank shaft 3. The combustion engine 2 is mounted inside a hull 101 of a ship 100 so that its crank shaft 3 is oriented in a horizontal direction. The crank shaft 3 is connected to a drive shaft 4 by means of an engine coupling 15. The engine coupling 15 is built and installed to compensate for radial, axial, or angular offset and for damping torsional vibrations.

[0026] 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. The upper transmission unit 5 comprises a forward clutch 8 and a reverse clutch 9 to transmit driving power from the drive shaft 4 to the vertical shaft 6 selectively in a forward or reverse direction by engaging the corresponding clutch 8 or 9. The forward clutch 8 and the reverse clutch 9 are both pressure-operated multi-disc clutches. An outer disc carrier of the forward clutch 8 and outer disc carrier of the reverse clutch 9 are rigidly connected to the drive shaft 4. A first inner disc carrier of the forward clutch 8 is rigidly connected to a first bevel pinion 16, while a second inner disc carrier of the reverse clutch 9 is rigidly connected to a second bevel pinion 17. Both bevel pinions 16, 17 are permanently meshing with a crown gear 18 which is fastened to the upper end of the vertical shaft 6.

[0027] The hybrid pod drive assembly 1 can be operated solely by one or both electric machines 10, 20 in forward and reverse direction, when both clutches 8 and 9 are disengaged. In such a pure electric operating mode it is possible to maneuver forward and reverse by the power of one or both electric machines 10, 20 without any further interaction with the clutches 8, 9 in the upper transmission unit 5.

[0028] A lower transmission unit 7 transmits the power from the vertical shaft 6 to a horizontal first propeller shaft 12 and to a horizontal second propeller shaft 22 in a way to rotate the first and the second propeller shafts 12, 22 in opposite rotational directions from one another. Hence, the rear propeller 13 is contrarotating to the front propeller 23. The lower transmission unit 7 comprises a further bevel gear set to generate the inverse rotation of the front propeller 23 and the rear propeller 13 which are disposed at the trailing end of a pod housing 19 so that axial lines of the front propeller 23 and the rear propeller 13 coincide with each other. Hence, the two propellers 13 and 23 generate a propulsive force while being rotated in opposite directions.

[0029] The hybrid pod drive assembly 1 further comprises a first electric machine 10 with a first rotor shaft 11 and a second electric machine 20 with a second rotor shaft 21. The second propeller shaft 22 is a hollow shaft which surrounds the first propeller shaft 12. A rear propeller 13 is mounted to a trailing end of the first propeller shaft 12 and a front propeller 23 is mounted to a trailing end of the second propeller shaft 22. This means that the rear propeller 13 and the front propeller 23 are acting as pushing propellers when the water vessel 100 is propelled in a forward direction.

[0030] Both electric machines 10 and 20 are arranged in the pod housing 19 which is mounted underneath the bottom of the hull 101. The first rotor shaft 11, i.e. the rotor shaft of the first electric machine 10, is arranged coaxial to the first propeller shaft 12 and connected to the first propeller shaft 12 via a first speed reduction gear 14. The speed reduction gear 14 is a planetary gear unit. A sun gear of the speed reduction gear 14 is rigidly connected to the first rotor shaft 11, while a planet carrier of the speed reduction gear 14 is permanently connected to the first propeller shaft 12. These connections provide for optimum rotation speed at the rear propeller 13 when the first electric machine 10 is operated as an electric motor to drive the rear propeller 13 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.

[0031] The second rotor shaft 21, i.e. the rotor shaft of the second electric machine 20, is coaxial and permanently connected to the second propeller shaft 22. In other embodiments the second rotor shaft 21 may be connected to the second propeller shaft 22 via a further speed reduction gear.

[0032] In the pod housing 19 the lower transmission unit 7 is mounted between the first electric machine 10 and the second electric machine 20 in axial direction. In a forward cruising direction of the water vessel 100 the first electric machine 10 is positioned in front of the lower transmission unit 7, while the second electric machine 20 is positioned behind the lower transmission unit 7. The axial direction is related to the rotating axis of the first and second propeller shafts 12, 22.

[0033] The second propeller shaft 22 is rotatably supported in the pod housing 19 and the first propeller shaft 12 is rotatably supported in the second propeller shaft 22, so that both propeller shafts 12 and 22 are directly or indirectly supported in the pod housing 19.Referals

[0034] 1hybrid pod drive assembly 2combustion engine 3crank shaft 4drive shaft 5upper transmission unit 6vertical shaft 7lower transmission unit 8forward clutch 9reverse clutch 10first electric machine 11first rotor shaft 12first propeller shaft 13rear propeller 14first speed reduction gear 15engine coupling 16first bevel pinion 17second bevel pinion 18crown gear 19pod housing 20second electric machine 21second rotor shaft 22second propeller shaft 23front propeller 100water vessel 101hull 102hybrid pod drive

Claims

1. Hybrid pod drive assembly (1) comprising a horizontal drive shaft (4) which can be driven by a combustion engine (2) and which is connectable to a vertical shaft (6), a lower transmission unit (7) to transmit the power from the vertical shaft (6) to at least a first propeller shaft (12), the hybrid pod drive assembly (1) further comprising a first electric machine (10) with a first rotor shaft (11) which is coaxial with the first propeller shaft (12) and connected to the first propeller shaft (12), the hybrid pod drive assembly (1) further comprising a second electric machine (20) with a second rotor shaft (21) which is coaxial with a second propeller shaft (22) and connected to the second propeller shaft (22), wherein the second propeller shaft (22) is surrounding the first propeller shaft (12), wherein a rear propeller (13) is mounted to a trailing end of the first propeller shaft (12), and wherein a front propeller (23) is mounted to a trailing end of the second propeller shaft (22).

2. Hybrid pod drive assembly (1) according to claim 1, wherein the lower transmission unit (7) is arranged to transmit the power from the vertical shaft (6) to the first propeller shaft (12) and to the second propeller shaft (22) in a way to rotate the first and the second propeller shafts (12, 22) in opposite rotational directions from one another.

3. Hybrid pod drive assembly (1) according to claim 1 or 2, wherein the lower transmission unit (7) is mounted between the first electric machine (10) and the second electric machine (20) in axial direction.

4. Hybrid pod drive assembly (1) according to one of the preceding claims, wherein the first rotor shaft (11) is connected to the first propeller shaft (12) via a first speed reduction gear (14) and / or the second rotor shaft (21) is connected to the second propeller shaft (22) via a further speed reduction gear.

5. Hybrid pod drive assembly (1) according to one of the preceding claims, wherein an upper transmission unit (5) is arranged to transmit the power from the drive shaft (4) to the vertical shaft (6) and wherein the upper transmission unit (5) comprises a forward clutch (8) and a reverse clutch (9).

6. Hybrid pod drive (102) comprising a hybrid pod drive assembly (1) according to one of the preceding claims and the combustion engine (2).

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