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The present invention relates to a marine propulsion device with two electric machines and to a water vessel with such a propulsion device.
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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 systems and all-electric systems.
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In the
WO 2012/035914 A1 a marine propulsion apparatus is described with a transmission mechanism which uses bevel gear units for changing the power transmission direction of drive shafts, and which transmits drive power from drive power sources disposed in the ship body to a propeller of a pod. The marine propulsion apparatus is provided with a pair of electric motors which are disposed onboard as drive power sources. The transmission mechanism drives the propeller by transmitting drive power from a pair of onboard horizontal drive shafts, which are respectively connected to the electric motors, to a vertical drive shaft by way of an upper bevel gear set. The drive power is further transmitted from the vertical drive shaft to a horizontal propeller shaft in the pod by way of a lower bevel gear set in the pod.
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The purpose of the present invention is to provide an improved marine propulsion device with a first and a second electric machine, which can be effectively used in a wide range of applications. Further a corresponding water vessel shall be provided.
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This purpose is achieved by a marine propulsion device according to claim 1 and by a water vessel according to claim 10. Further embodiments are claimed in dependent claims.
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The present invention provides a marine propulsion device comprising a first electric machine with a first motor shaft, a horizontal drive shaft coupled to the first motor shaft and an upper bevel gear set to transmit propulsion power from the horizontal drive shaft to a vertical shaft. The first motor shaft can be coaxial to the horizontal drive shaft. The first motor shaft can be directly coupled to the horizontal drive shaft or via other components like a coupling for vibration damping or to adjust possible misalignments. The proposed marine propulsion device comprises further a second electric machine with a second motor shaft. The second motor shaft is coupled to the vertical shaft and the second motor shaft is arranged parallel to the vertical shaft. This means, that the second motor shaft is not coaxial, but parallel and positioned with an offset to the vertical shaft. This way, the whole second electric motor can be arranged with a horizontal offset regarding to the vertical shaft. Such an arrangement allows for a compact design of the marine propulsion system in axial and in a vertical direction. This can be beneficial to fit the marine propulsion device in a restricted space inside the hull of a water vessel. With the two electric machines, a water vessel can be driven solely on electric power, i.e. without a combustion engine. Environmental risks and costs incurred using diesel combustion engines can be avoided with such an all-electric propulsion device. All-electric propulsion devices are useful to cruise in protected areas or no-wake areas with low noise and zero emission.
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The first and second motor shafts are part of the corresponding electric machine and can be rigidly connected to a rotor of the corresponding electric machine. The terms horizontal and vertical refer to a marine propulsion device 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 from an exact horizontal or vertical direction up to an angle of 15 degrees. Hence, the terms horizontal and vertical can be understood as approximate designations.
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The marine propulsion device may comprise a lower bevel gear set to transmit propulsion power from the vertical shaft to a propeller shaft supported in an underwater housing. The underwater housing can be a pivotable housing of a pod for steering the corresponding water vessel in a desired heading.
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The second electric machine can be supported by an intermediate casing, which is fastened to a housing of the upper bevel gear set. The intermediate casing may comprise a mounting flange which can be mounted to a counterflange of the housing of the upper bevel gear set. The mounting flange of the intermediate casing can be adapted to a counterflange of a conventional housing of an upper bevel gear set. This allows an easy implementation of a second electric machine in a conventional marine propulsion device with only one first electric machine. The second electric machine together with the intermediate casing can be easily implemented as one module of a modular system, with the benefit of increased flexibility and variety of marine propulsion devices reusing such a module in different arrangements.
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The second motor shaft can be coupled to the vertical drive shaft by means of a spur gear set. The spur gear set may have one or more gear steps. In one embodiment with two gear steps the spur gear set consists of three spur gears. A driving spur gear is fastened to the second motor shaft. A driven spur gear is fastened to the vertical shaft. An intermediate spur gear is arranged in between the driving and the driven spur gears and meshing with both.
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The spur gear set can be encased in the intermediate casing. In other words the intermediate casing forms a housing for the spur gear set. This way the intermediate casing can protect the spur gear set from detrimental influence of the environment and, at the same time, the intermediate casing can hold a fluid for cooling and lubricating of the spur gear inside. Therefore appropriate sealing means can be provided at the interfaces to the adjacent components. The intermediate casing can comprise a sealing interface to hold a sealing against water leakage, as an example.
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In one embodiment the intermediate casing is used to fasten the marine propulsion device to the hull of the corresponding water vessel. For this the intermediate casing comprises at least one fastening element to fasten the intermediate casing to a support structure of a hull. Such a fastening element can be a flange, a mounting eye or any kind of a carrying bracket, just to name a few examples. There may be arranged several such fastening elements at the intermediate casing.
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According to one embodiment, the marine propulsion device comprises a control system, which is configured to independently control the operation of the first electric machine and the second electric machine. Each of the two electric machines may have its dedicated power electronic means like inverters and/or controllers. An independent control of the two electric machines allows for different operating modes. The control system can be configured to control operation of the marine propulsion device in three operation modes. A first operating mode using only the first electric machine for propulsion, a second operating mode using only the second electric machine for propulsion and a third operating mode using the first and the second electric machines for propulsion.
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Additional operating modes can be applied, including the operation of the first or the second electric machine in a generator mode to generate electric energy. The generated electric energy can be used to charge a battery or to feed other electric consumers of the corresponding water vessel. When the marine propulsion device is applied as a sail drive the effect of hydrogeneration can be used during sailing, when the propeller is driven by the water streaming through the propeller area. Hence, the propeller drives the vertical shaft via the propeller shaft. The first or the second electric machine can be switched to a generator mode and electric energy is generated. The generated electric energy can be used to recharge a battery or to feed other electric consumers.
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In view of efficient operation, the first electric machine and the second electric machine may have different nominal power. Beneficially the first electric machine may have a power range of 30 to 110 Kilowatt and the second electric machine may have a power range of about 30 to 60 Kilowatt. There may be also applied different voltages at the first and the second electric machine. One of the machines might be operated in a high voltage range between 360 and 400 Volt, while the other electric machine is operated at a low voltage of about 48 Volt. An appropriate size and nominal power of the first and the second electric machine can be chosen to meet the requirements of the individual application.
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The control system shall be arranged to select the appropriate operation modes depending on the current power demand, which again depends on the required rotational speed of the propeller. Hence, each of the two electric machines can be related to specific speed ranges of the propeller or a propeller shaft. The control system may operate the marine propulsion system in a so-called Eco-Mode, wherein the first electric machine only runs when a required power exceeds a maximum power of the second electric machine, or vice versa. In many operational phases it might be sufficient to run only one of the two electric machines, which reduces operation time and maintenance efforts at the other electric machine and energy consumption of the marine propulsion device.
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Further embodiments comprise at least one of a first clutch and a second clutch, wherein the first clutch is arranged to selectively connect and disconnect the vertical shaft and the first motor shaft, and wherein the second clutch is arranged to selectively connect and disconnect the vertical shaft and the second motor shaft.
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Said first and second clutch can be arranged in one clutch assembly, wherein a clutch member can be moved to a first switching position to connect the vertical shaft with the first motor shaft or to a second switching position to connect the vertical shaft with the second motor shaft. Additionally a third switching position can be arranged to disconnect the vertical shaft from the first motor shaft and the second motor shaft. The third switching position is a neutral position or idle position. In the neutral position the vertical shaft can not be driven by neither the first electric machine nor the second electric machine.
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The first clutch and/or the second clutch can be pressure operated or electrically operated. The first and/or the second clutch can be controlled by the control system. This way, the control system may disconnect this electric machine from the vertical shaft which is not operational in the first or second operation mode. In first operating mode as described above, the second electric machine can be disconnected from the vertical shaft, whereas in the second operating mode, the first electric machine can be disconnected from the vertical shaft. Subsequently the frictional losses will be reduced, due to less components being driven and rotating in the corresponding operation mode.
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The proposed marine propulsion device can generally be applied in different marine propulsion systems like stern drives, Z-drives or pod drives. The invention relates further to a water vessel with a marine propulsion device as described above.
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The invention and its benefits will be further described in the following, by way of example only, and with reference to the accompanying figure.
- Fig. 1
- shows a marine propulsion device according to the invention in a sectional drawing and
- Fig. 2
- shows a perspective view of another embodiment of a marine propulsion device according to the invention.
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The embodiment of Fig. 1 shows a marine propulsion device 1 which is mounted to a hull 101 of a water vessel 100. Fig. 1 shows only a section of the bottom of the hull 101. An upper part of the marine propulsion device 1 including a first electric machine 10 and a second electric machine 20 is positioned inside the hull 101, whereas a lower part including a propeller 9 of the marine propulsion device 1 is positioned outside and underneath the hull 101.
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A first motor shaft 11 of the first electric machine 10 is coupled to a horizontal drive shaft 2 which is an input shaft to an an upper bevel gear set 3. The power from the first motor shaft 11 is transmitted via the horizontal drive shaft 2 and the upper bevel gear set 3 to a vertical shaft 5. A lower bevel gear set 6 is arranged underneath the hull 101 to transmit propulsion power from the vertical shaft 5 to a horizontal propeller shaft 7, which is supported in an underwater housing 8. The vertical shaft 5 in this example is made of an upper shaft section and a lower shaft section which are rigidly connected to each other. In the
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The second electric machine 20 comprises a second motor shaft 21 which is arranged parallel to the vertical shaft 5, so that the second electric machine 20 is arranged in a vertical direction. The second motor shaft 21 is coupled to the vertical shaft 5 by means of a spur gear set 23, which is encased in an intermediate casing 22. The second electric machine 20 is supported by said intermediate casing 22. The intermediate casing 22 is fastened to the housing 4 of the upper bevel gear set 3. The spur gear set 23 comprises two gear steps. A driving spur gear 24 is fastened to the second motor shaft 21. A driven spur gear 26 is fastened to the vertical shaft 5. An intermediate spur gear 25 is arranged in between the driving spur gear 24 and the driven spur gear 26 and meshes with both. The intermediate spur gear 25 is supported in the intermediate casing 22.
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The marine propulsion device 1 comprises further a first clutch 12 and a second clutch 13, which are shown schematically in Fig. 1. In this embodiment the first clutch 12 and the second clutch 13 are both form-fitting clutches. The first clutch 12 and the second clutch 13 are part of one clutch assembly 14. A switching member of the clutch assembly 14 can be moved to different switching positions to connect the first motor shaft 11 and/or the second motor shaft 21 to the vertical shaft 5. In other embodiments the first clutch 12 and the second clutch 13 can be separate clutches, wherein the first clutch 12 is arranged to selectively connect and disconnect the vertical shaft 5 and the first motor shaft 11, and wherein the second clutch 13 is arranged to selectively connect and disconnect the vertical shaft 5 and the second motor shaft 21.
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A control system 30 is provided to independently control the operation of the first electric machine 10 and the second electric machine 20. The control system 30 is configured to control operation of the marine propulsion device 1 in several operation modes, a first operating mode using only the first electric machine 10 for propulsion, a second operating mode using only the second electric machine 20 for propulsion and a third operating mode using the first and the second electric machines 10, 20 simultaneously for propulsion. Control system 30 can also control the actuation of the first clutch 12 and the second clutch 13 in order to adjust a requested operation mode.
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Fig. 2 shows another embodiment of a marine propulsion device 1, wherein the same numbers are used to indicate the same components with regard to Fig. 1. The intermediate casing 22 comprises fastening elements 27, 28, 32 to fasten the intermediate casing 22 to the hull 101. The fastening elements 27, 28, 32 in this embodiment comprise a first support bracket 27, a second support bracket 28 and a mounting plate 32. The mounting plate 32 can be mounted to a corresponding flange at the hull 101. A sealing 29 is arranged to seal a gap 31 between the marine propulsion system 1 and the hull 101 against water leakage. The sealing 29 is attached to the mounting plate 32.
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A support frame 15 is arranged to fasten the first electric machine 10 inside the hull 101.
Referals
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- 1
- marine propulsion device
- 2
- horizontal drive shaft
- 3
- upper bevel gear set
- 4
- housing
- 5
- vertical shaft
- 6
- lower bevel gear set
- 7
- propeller shaft
- 8
- underwater housing
- 9
- propeller
- 10
- first electric machine
- 11
- first motor shaft
- 12
- first clutch
- 13
- second clutch
- 14
- clutch assembly
- 15
- support frame
- 20
- second electric machine
- 21
- second motor shaft
- 22
- intermediate casing
- 23
- spur gear set
- 24
- driving spur gear
- 25
- intermediate spur gear
- 26
- driven spur gear
- 27
- fastening element, support bracket
- 28
- fastening element, support bracket
- 29
- sealing
- 30
- control system
- 31
- gap
- 32
- fastening element, mounting plate
- 100
- water vessel
- 101
- hull