Marine hybrid transmission and marine hybrid drive

Abstract

The present invention relates to a marine hybrid transmission (1) comprising a first input shaft (11) to be connected to a combustion engine (10) and a second input shaft (21) to be connected to an electric machine (20). The first input shaft (11) is arranged coaxially to the second input shaft (21) and the first input shaft (11) is connectable to an output shaft (30) by means of at least one clutch (2, 3). The second input shaft (21) is permanently connected to the output shaft (30). The invention further relates to a marine hybrid drive (100) with such a marine hybrid transmission (1).

Description

[0001] The present invention relates to a marine hybrid transmission and to a marine hybrid drive.

[0002] 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.

[0003] 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 marine vessel.

[0004] 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.

[0005] 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.

[0006] This purpose is achieved by a marine hybrid transmission according to claim 1 and by a marine hybrid drive according to claim 8. Further embodiments are claimed in dependent claims.

[0007] The present invention provides a marine hybrid transmission comprising a first input shaft to be connected to a combustion engine and a second input shaft to be connected to an electric machine. The first input shaft is arranged coaxially to the second input shaft. A coaxial arrangement of the first and second input shaft is beneficial to a compact outline of the marine hybrid transmission. The first input shaft is connectable to the output shaft by means of at least one clutch, while the second input shaft is permanently connected to the output shaft. The clutch may be part of a clutch assembly to reverse the direction of rotation between the first input shaft and the output shaft. Such a clutch provides for a propulsion of the marine vessel in a forward and in a reverse direction by the combustion engine.

[0008] The effect of the permanent connection between the second input shaft and the output shaft is, that the output shaft and a propeller connected to the propeller shaft can be controlled and driven by the electric machine, independent of a status of the combustion engine or components of the marine hybrid transmission, especially independent of the status of the clutch. Therefore it is possible to establish independent control systems for the electric machine and the marine hybrid transmission.

[0009] Clutches in marine transmissions are typically pressure operated clutches. In case of a failure in the pressure supply to such a clutch, the power from the first input shaft cannot be transmitted to the output shaft. The present invention enables to drive the output shaft in such a situation 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.

[0010] 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.

[0011] Another mode of operation is a booster-mode, which adds the output power of the electric machine to the combustion engine power output. This is possible 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 by using the electric machine for small accelerations or changes in speed.

[0012] To reduce the required space of the marine hybrid transmission, the second input shaft can be a hollow shaft and the first input shaft can be arranged to extend through the second input shaft. With other words the first input shaft runs through the inner space of the second input shaft in form of the hollow shaft.

[0013] A motor shaft of the electric machine can be arranged parallel to the first input shaft. The motor shaft can be connected to the second input shaft by means of a belt drive with a pulley on each shaft or by a set of gears, especially spur gears.

[0014] The marine hybrid transmission may further comprise a first gear to transmit driving power to the output shaft in a first direction of rotation and a second gear to transmit driving power in an opposing second direction of rotation. First and second directions of rotations may be a forward and a reverse direction. The second input shaft can be permanently connected to the output shaft via the first gear or via the second gear. Said first and second gears can be spur gears, to connect the input shaft with an output shaft which is at least nearly parallel to the input shaft. Said first and second gears can also be bevel gears, to connect a horizontal first input shaft to a vertical output shaft. The later arrangement is typically used for so-called Z-drives, for example in thrusters or pod-drives. The second input shaft can be directly connected to the first gear, i.e. without any other element between them. The direct connection can be realized preferably by means of a splined connection, which provides for a compact and reliable connection.

[0015] In one embodiment the marine hybrid transmission comprises a housing to enclose the first gear, the second gear and the clutch. This way the marine hybrid transmission forms a compact and robust structural unit. Besides, the housing protects the components inside from harmful influence of the surrounding, like humidity, water or dust and keeps lubrication fluid safely inside the housing.

[0016] According to a further embodiment the first input shaft and the second input shaft are arranged on an input side, and wherein the output shaft is arranged on an output side opposed to the input side. Hence, there is each one connection point to the first and second input shaft on the input side, while another connection point for the output shaft is on the opposing output side. Such a layout of the marine hybrid transmission can be used in applications, where the available space does not allow to position the electric machine on the opposite side of the combustion engine at the marine hybrid transmission.

[0017] The present invention provides a marine hybrid transmission with an optimal integration between the combustion engine and the electric machine. The described design provides that the electric motor is installed in the limited space of an engine room with a direct engagement to the coaxial second input shaft.

[0018] The invention further comprises a marine hybrid drive with a combustion engine, with an electric machine and with a marine hybrid transmission as described above. Depending on the requirements of the specific application, the electric machine can be a low voltage machine to be operated for example on 48 Volt or it can be a high voltage machine to be operated in a range between 360 and 400 Volt. The proposed marine hybrid drive can be used for thrusters, pod drives, saildrives or marine shaft devices, just to name a few exemplary applications.

[0019] 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. 1shows a marine hybrid drive with a combustion engine, with an electric machine and with a marine hybrid transmission according to the invention in a schematic drawing and Fig. 2shows a sectional view of a marine hybrid transmission according to the invention.

[0020] The marine hybrid drive 100 as shown in Fig. 1 comprises a combustion engine 10, an electric machine 20 and a marine hybrid transmission 1. The marine hybrid drive 100 is mounted in an engine room inside a hull 101 of a marine vessel.

[0021] The marine hybrid transmission 1 comprising a first input shaft 11 which is connected to a crank shaft 12 of the combustion engine 10 and a second input shaft 21 is connected to the electric machine 20. A motor shaft 22 of the electric machine 20 runs parallel to the first input shaft 11.

[0022] The first input shaft 11 is arranged coaxially to the second input shaft 21. The second input shaft 21 is a hollow shaft and the first input shaft 11 centrally extends through the second input shaft 21. Hence, the first input shaft 11 is partially arranged inside the second input shaft 21. Such a coaxial arrangement of the first input shaft 11 and the second input shaft 21 allows for a compact layout of the marine hybrid transmission 1.

[0023] The first input shaft 11 can be connected to an output shaft 30 of the transmission 1 by means of a clutch assembly 4 comprising a first clutch 2 and a second clutch 3. The first input shaft 11, the second input shaft 21 and the output shaft 30 are supported in a housing 7 of the marine hybrid transmission 1. The housing 7 further encloses the clutch assembly 4 and several spur gears 5, 6, 24, 31, 32, 33. There is a flange mounted to the trailing end of the output shaft 30. This flange provides for a connection point 34 to connect the output shaft 30 to a propeller shaft of the marine vessel.

[0024] When the combustion engine 10 is operating, a first gear 5 transmits driving power from the first input shaft 11 to the output shaft 30 in a forward direction of rotation, when the first clutch 2 is engaged. The first gear 5 is meshing with a first output gear 31 which is fastened to the output shaft 30. A second gear 6 transmits driving power from the first input shaft 11 to the output shaft 30 in a reverse direction of rotation, when the second clutch 3 is engaged. The second gear 6 is meshing with a reversing gear 33 which is also meshing with a second output gear 32 on the output shaft 30.

[0025] When the electric machine 20 is operating as an electric motor, the power of the electric machine 20 is transmitted via the second input shaft 21, the first gear 5 and the first output gear 31 to the output shaft 30. The second input shaft 21 is permanently connected to the output shaft 30 via the first gear 5 and the first output gear 31. The electric machine 20 alone can drive the output shaft 30 in a forward or in a reverse direction when the first clutch 2 and the second clutch 3 are disengaged. This way an electric cruising is enabled, especially to cruise protected areas with low noise and zero emission. It is possible to drive the water vessel with zero noise and zero pollution during docking maneuvers and during no-wake cruising in the pure electric drive mode.

[0026] Another option is to drive the output shaft 30 in a boost mode by the combustion engine 10 and the electric machine 20 together. Therefore, the first clutch 2 or the second clutch 3 has to be engaged.

[0027] Another option is to operate the electric machine 20 in a generator mode to generate electric energy for charging a battery or to provide electric energy to other consumers on the marine vessel. The electric machine 20 can be driven by the power of the combustion engine 10 when one of the clutches 2 or 3 is engaged. If the transmission is installed on a sailboat, the output shaft 30 can rotate for the effect of the propeller and effect a so-called hydrogeneration during sailing. Such a charge mode from sailing cruising can also be used to recharge the batteries, provided that a sailboat speed is greater than 3-4 knots that comport a rotation of the propeller for the drag effect at the propeller.

[0028] A motor shaft 22 of the electric machine 20 runs parallel to the second input shaft 21. The motor shaft 22 is connected to the second input shaft 21 via a set of spur gears 23 and 24. The electric machine 20 is positioned on a side of the marine hybrid transmission 1, so that the electric machine 20 does not extend over the axial length of the marine hybrid transmission 1. This can be beneficial for a compact layout in axial direction when the space inside the hull is limited in the axial direction.

[0029] The first input shaft 11 is arranged on an input side 8 of the marine hybrid transmission 1, while the output shaft 30 is arranged on an output side 9 opposed to the input side 8.

[0030] A further embodiment of the marine hybrid transmission 1 is shown in Fig. 2. The principal layout of this marine hybrid transmission 1 is the same as shown in the embodiment of Fig. 1. Therefore, the same referal numbers are used for the same elements.

[0031] The driving connection between the electric machine 20 and the second input shaft 21 is realized by a belt drive in the embodiment of Fig. 2. For this, a belt pulley 25 is fixed to the second input shaft 21.

[0032] Fig. 2 further shows some details of the second input shaft 21 and its permanent connection with the first gear 5. The second input shaft 21 is directly connected to the first gear 5 by a splined connection 29 which is formed on an extension 28 of the first gear 5. Such a direct connection between the second input shaft 21 and the first gear 5 allows for a compact layout and a reliable function.

[0033] The second input shaft 21 is a hollow shaft which is supported in the housing 7 by a first bearing 26 on the input side 8 of the marine hybrid transmission 1. The first bearing 26 is a double-row ball bearing. At the inner surface of the second input shaft 21 there is a second bearing 13 located to support the first input shaft 11 inside the second input shaft 21. The second bearing 13 is a needle bearing. The first input shaft 11 is further supported in the housing 7 on the output side 9 by means of a third bearing 27, which is a double-row angular ball bearing.Referals

[0034] 1marine hybrid transmission 2clutch 3clutch 4clutch assembly 5first gear 6second gear 7housing 8input side 9output side 10combustion engine 11first input shaft 12crank shaft 13second bearing 20electric machine 21second input shaft 22motor shaft 23spur gear 24spur gear 25belt pulley 26first bearing 27third bearing 28extension 29splined connection 30output shaft 31first output gear 32second output gear 33reversing gear 34output connection 100marine hybrid drive 101hull

Claims

1. Marine hybrid transmission (1) comprising a first input shaft (11) to be connected to a combustion engine (10) and a second input shaft (21) to be connected to an electric machine (20), wherein the first input shaft (11) is arranged coaxially to the second input shaft (21), wherein the first input shaft (11) is connectable to an output shaft (30) by means of at least one clutch (2, 3) and wherein the second input shaft (21) is permanently connected to the output shaft (30).

2. Marine hybrid transmission (1) according to claim 1, wherein the second input shaft (21) is a hollow shaft, and wherein the first input shaft (11) extends through the second input shaft (21).

3. Marine hybrid transmission (1) according to claim 1 or 2, wherein the electric machine (20) comprises a motor shaft (22) which is arranged parallel to the first input shaft (11).

4. Marine hybrid transmission (1) according to one of the preceding claims, wherein the marine hybrid transmission (1) comprises a first gear (5) to transmit driving power from the first input shaft (11) to the output shaft (30) in a forward direction of rotation and a second gear (6) to transmit driving power from the first input shaft (11) to the output shaft (30) in a reverse direction of rotation, and wherein the second input shaft (21) is permanently connected to the output shaft (30) via the first gear (5).

5. Marine hybrid transmission (1) according to claim 4, wherein the second input shaft (21) is directly connected to the first gear (5) by means of a splined connection (29).

6. Marine hybrid transmission (1) according to claim 4 or 5, wherein the marine hybrid transmission (1) comprises a housing (7) to enclose the first gear (5), the second gear (6) and the at least one clutch (2, 3).

7. Marine hybrid transmission (1) according to one of the preceding claims, wherein the first input shaft (11) and the second input shaft (21) are arranged on an input side (8), and wherein the output shaft (30) is arranged on an output side (9) opposed to the input side (8).

8. Marine hybrid drive (100) with a combustion engine (10), with an electric machine (20) and with a marine hybrid transmission (1) according to one of the preceding claims.

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