MARINE DRIVE UNIT AND MARINE VESSEL

Abstract

A hybrid marine drive unit mounted to a transom. The drive unit includes a drive housing mounted on the transom, a propelling unit rotatable about a vertical axis and mounted to a lower surface of the drive housing, and a transmission with at least a vertical drive shaft located in the drive housing and extending into the propelling unit. The vertical drive shaft is arranged transmit drive torque from at least one of multiple sources of drive torque. The vertical drive shaft is operably connected to a first source of drive torque arranged within the drive housing, and the vertical drive shaft is operably connected to a horizontal output shaft extending into the drive housing through the transom. The horizontal output shaft is connectable to a second source of drive torque.

Claims

1. Hybrid marine drive unit mounted to a transom, which drive unit comprises a drive housing rigidly mounted on the transom, a propelling unit rotatable about a vertical axis and mounted to a lower surface of the drive housing, and a transmission with at least a vertical drive shaft located in the drive housing and extending into the propelling unit, which vertical drive shaft is arranged to transmit drive torque from at least one of multiple sources of drive torque, wherein: the drive unit is an azimuthing pod drive removably attached to the transom the vertical drive shaft is operably connected to at least one first source of drive torque arranged within the drive housing, and that the vertical drive shaft is operably connected to a horizontal output shaft extending into the drive housing through the transom, wherein the horizontal output shaft is connectable to a second source of drive torque.

2. Hybrid marine drive unit according to claim 1, wherein the first source of drive torque is an electric motor with an independently excited rotor; wherein the rotor is arranged to be freewheeling when its excitation current is deactivated.

3. Hybrid marine drive unit according to claim 2, wherein the at least one electric motor is a polyphase synchronous motor, a switched reluctance motor or a synchronous reluctance motor.

4. Hybrid marine drive unit according to claim 1, wherein the at least one first source of drive torque is operably connected to the upper end of the vertical drive shaft above a gear unit.

5. Hybrid marine drive unit according to claim 1, wherein the at least one electric motor is directly connected to the propelling unit via the vertical drive shaft.

6. Hybrid marine drive unit according to claim 1, wherein the at least one electric motor is operably connected to the vertical drive shaft by a gear unit.

7. Hybrid marine drive unit according to claim 6, wherein the first and second sources of drive torque are operably connected to the vertical drive shaft via the gear unit.

8. Hybrid marine drive unit according to claim 1, wherein the horizontal output shaft is operably connected to the vertical drive shaft via the gear unit.

9. Hybrid marine drive unit according to claim 3, wherein the gear unit comprises opposing bevel gears operatively connected to the horizontal output shaft, wherein each bevel gear is connected or disconnected to the vertical drive shaft by a controllable actuator.

10. Hybrid marine drive unit according to claim 9, wherein the controllable actuator is a clutch.

11. Hybrid marine drive unit according to claim 1, wherein each source of drive torque is arranged to drive the vertical drive shaft independently or in combination.

12. Hybrid marine drive unit according to claim 1, wherein the drive housing comprises a control unit and power electronic controller for the at least one electric motor.

13. Hybrid marine drive unit according to claim 1, wherein the drive housing comprises a steering system with a control unit and a steering drive unit for rotating the propelling unit about its vertical axis.

14. Marine vessel with a hybrid driveline comprising multiple sources of drive torque to propel the vessel, wherein the vessel is provided with at least one hybrid marine drive unit according to claim 1.

15. Marine vessel according to claim 14, wherein the at least one hybrid marine drive unit comprises at least one electric motor arranged within a drive housing and that the drive unit is operatively connected to an internal combustion engine arranged within the hull of the vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. In the drawings:

[0022] FIG. 1 shows a lower perspective view of a schematically illustrated vessel comprising a pair of drive units;

[0023] FIG. 2 shows a schematic side view of a driveline according to a first example;

[0024] FIG. 3 shows a schematic side view of a driveline according to a second example;

[0025] FIG. 4 shows a schematic side view of a driveline according to a third example;

[0026] FIG. 5 shows a schematic transmission for the driveline in FIG. 2;

[0027] FIG. 6 shows a schematic transmission for the driveline in FIG. 3; and

[0028] FIG. 7 shows a schematic transmission for the driveline in FIG. 4.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0029] FIG. 1 shows a lower perspective view of a schematically illustrated marine vessel 100 comprising two marine drive units 103, 103′ according to the invention. In this example, the marine drive units 103, 103′ are identical and only one will be described in further detail below. The marine drive units 103, 103′ are mounted to a transom 102 on the vessel 100. Each marine drive unit 103, 103′ comprises an upper and a lower unit, wherein the upper unit is a drive housing 104, 104′ rigidly mounted on the transom 102. The lower unit is a propelling unit 105, 105′ rotatable about a vertical axis and mounted to a lower surface 106, 106′ of each drive housing 104, 104′. The schematically indicated marine drive units 103, 103′ in FIG. 1 are preferably located below the waterline of the vessel hull 101. The example shown in FIG. 1 shows propelling units in the form of steerable pods which comprise twin forward facing, pulling propellers 107, 107′. As will be described below, alternative propelling units can be employed within the scope of the invention.

[0030] The marine drive units in FIG. 1 are controllable by a control means (not shown) such as a throttle lever located at an operating position on-board the vessel. The throttle lever can be connected to an electronic control unit (ECU) via suitable wiring, which ECU is connected to a source of energy, such as a battery pack or a fuel cell via additional wiring. Such an energy source is located within the hull of the vessel and can comprise a power electronic controller (PEC) and an electronic controller for calibrating and charging a battery pack. The throttle lever be used for controlling the first source of drive torque, such as at least one electric motor within the drive housing, and the second source of drive torque, such as an engine located within the hull of the vessel. The first and second sources of drive torque form a hybrid driveline and the sources can be operated individually or together. Electronic controllers of this type are known in the art and will not be shown or described in further detail here.

[0031] FIG. 2 shows a cross-sectional side view of a drive unit 203 according to a first example shown in FIG. 1. FIG. 2 shows the drive unit 203 mounted to a transom 202 of a marine vessel (see FIG. 1). The drive unit 203 comprises an upper drive housing 204, and a lower propelling unit 205, where the propelling unit 205 is rotatably mounted to a lower surface 206 of the drive housing 204 in order to steer the vessel. The drive housing 204 encloses a transmission comprising a vertical drive shaft 210 arranged transmit drive torque from at least one source of drive torque to a pair of forward-facing counter rotating propellers 207 on the propelling unit 205. The transmission further comprises a gear unit 213 operably connectable to an upper end of the vertical drive shaft 210. In FIG. 2, a first source of drive torque is an electric motor 211 with a vertical output shaft 212 that is operably connected to the vertical drive shaft 210 directly through the gear unit 213. The electric motor 211 can be disconnected from the through shaft comprising the vertical drive shaft 210 and the vertical output shaft 212 by demagnetizing the rotor. A horizontal output shaft 220 is connected to a second source of drive torque in the form of an inboard ICE 221 located within the hull of the vessel (see FIG. 2).

[0032] The gear unit 213 comprises a set of bevel gears 214, 215, 216 which are in constant driving contact with each other. Each bevel gear is associated with a respective driving or driven shaft 212, 210, 220 and is switchable between a connected state and a disconnected state for transferring torque to the vertical drive shaft 210. The bevel gear 216 is fixed to the horizontal output shaft 220 and is switchable between a driven state and a freewheeling state by a main clutch 224 adjacent the ICE 221. Each bevel gear 214, 215 on the vertical drive shaft 210 is controllable between its connected and disconnected states by a corresponding actuatable clutch 214′, 215′ mounted adjacent the respective bevel gear (see FIG. 5). Switching can be achieved by actuation or deactuation of a suitable controllable clutch or mechanical actuator. In the subsequent text switching is performed using wet or dry multi-plate clutches, or lamella clutches, hereafter referred to as “clutches”. Lamella clutches of this type can be pneumatically or hydraulically actuated using a suitable source of fluid pressure. The design or control of such clutches is known in the art and will not be described in further detail here.

[0033] In FIGS. 2 and 6, the vertical output shaft 212 of the electric motor 211 passes through the gear unit 213. The gear unit 213 comprises an upper first bevel gear 214 arranged on the vertical output shaft 212 and a lower second bevel gear 215 arranged on the vertical drive shaft 210. The first and second bevel gears 214, 215 are in driving connection with the intermediate third bevel gear 216 arranged on the horizontal output shaft 220. The horizontal output shaft 220 is connected to a second source of drive torque in the form of an inboard ICE 221 located within the hull of the vessel (see FIG. 1). The horizontal output shaft 220 passes through a seal 222 in the transom 202 and is fixed in a vibration absorbing bushing 223 supported by the ICE output shaft. The clutch 224 is provided between the horizontal output shaft 220 and the ICE crankshaft to control the rotation of the horizontal output shaft 220. The first and second bevel gears 214, 215 are freely rotatable about the vertical output shaft 212 and the vertical drive shaft 210, respectively, in their disconnected state. Similarly, the third bevel gear 216 is freely rotatable with the horizontal output shaft 220 when the clutch 224 adjacent the ICE221 in its disconnected state. The bevel gears 214, 215 are selectably connected to the vertical drive shaft 210 in order to transmit torque from the ICE 221 to the vertical drive shaft 210 and the propellers. In this way, the vertical drive shaft 210 can be operably connected to the horizontal output shaft 220 which extends out of the drive housing 204 through the transom 202.

[0034] In operation, the driveline can be operated in electric mode using the electric motor 211 rotating the vertical output shaft 212 and the vertical drive shaft 210 directly as shown in FIGS. 2 and 5 to drive the vessel in a forward direction. FIG. 5 shows a schematic view of the transmission for the driveline in FIG. 2. In the electric mode, the rotor of the electric motor 211 is magnetized and the bevel gears 214, 215 are disconnected from the vertical drive shaft 210. Propelling the vessel in a reverse direction is achieved by switching the direction of rotation of the electric motor 211.

[0035] Alternatively, the driveline can be operated in ICE mode, wherein the rotor (not shown) of the electric motor 211 is demagnetized making the vertical output shaft 212 freely rotatable relative to the motor. In the gear unit 213, the first bevel gear 214 is maintained disconnected while the second bevel gear 215 is connected to the vertical drive shaft 210 by actuation of the clutch 215′. At the same time, the third bevel gear 216 is driven by the horizontal output shaft 220 by actuation of the main clutch 224. The ICE 221 can then be operated to transmit torque to the horizontal shaft 220 and the vertical drive shaft 210 via the third bevel gear 216 and the second bevel gear 215, in order to propel the vessel in a forward direction. In order to propel the vessel in a reverse direction the main clutch 224 is deactuated. The second bevel gear 215 is then disconnected by deactuation of the clutch 215′, while the first bevel gear 214 is connected to the vertical output shaft 212 by actuation of the clutch 214′. Subsequently, the third bevel gear 216 continues to be driven by the horizontal output shaft 220 by actuation of the main clutch 224. The ICE 221 can then be operated to transmit torque to the horizontal shaft 220 and the vertical drive shaft 210 via the third bevel gear 216 and the first bevel gear 214.

[0036] According to a further example, the driveline can be operated in a hybrid mode using the electric motor 211 and the ICE 221 together. In the hybrid mode, the gear unit 213 is operated in the same way as in the ICE mode described above, wherein the rotor of the electric motor 211 is magnetized so that the motor can be operated to drive the vertical output shaft 212 to assist the ICE 221. The direction of rotation of the electric motor 211 is selected to correspond with the direction of rotation of the currently connected first or second bevel gear 214, 215.

[0037] The propelling unit 205 contains a gearbox 208 operably connected to a lower end of the vertical drive shaft 210, which can be rotated as shown by the arrow Ai to drive the counter rotating propellers 207. Gearboxes for driving counter-rotating shafts of this type are well known and will not be described in further detail.

[0038] The drive housing 204 further comprises a control unit and power electronics controller (PEC) 230 for the electric motor 211. The combined control unit and power electronics controller (PEC) 230 is also used for controlling a steering arrangement 240 described below. The outer enclosure for the drive housing 204 provides a thermal mass to absorb the heat generated by the electric motor 211 and the PEC 230. In operation, the drive housing 204 is immersed in water and the water provides effective convection cooling. The electric motor 211 is connected to the PEC 230, which supplies current to the electric motor 211 from an inboard energy storage (not shown). Control means such as a throttle and a steering means (not shown) are provided at an operator station on-board the vessel.

[0039] The propelling unit 205 is arranged to be rotatable relative to the lower surface 206 of the drive housing by a steering arrangement 240 in order to steer the vessel. The steering arrangement 240 is located in the drive housing comprises a steering system with a control unit and a steering drive unit for rotating the propelling unit about its vertical axis. The steering drive unit can comprise an electric motor. The steering drive unit drives a steering transmission comprising a pinon gear that drives a gear fixed to the propelling unit 205 about the central axis X of the vertical drive shaft 210 as indicated by the arrow A2.

[0040] The drive housing 204 in FIG. 2 further comprises a coolant and lubricant circuit 250. FIG. 2 schematically indicates a closed coolant and lubrication circuit for the gear unit 213, the vertical drive shaft 210, the steering arrangement 240 and the electric motor 211. The closed coolant and lubrication circuit comprises a pump, a reservoir, a supply conduit connected to conduits for cooling the electric motor 211 and a conduit supplying the coolant/lubricant to the gear unit and steering arrangement. The provision of a closed coolant and lubrication circuit allows internal components to be cooled without using water from the surrounding body of water. As described above, the outer enclosure of the drive housing 204 can provide additional cooling by using it as a thermal mass to absorb the heat generated by the electric motor 211 and the PEC 230. The arrangement also allows the same system to be used for both cooling and lubrication.

[0041] FIG. 3 shows a schematic side view of a driveline according to a second example. FIG. 3 shows the drive unit 303 mounted to a transom 302 of a marine vessel (see FIG. 1). The drive unit 303 comprises an upper drive housing 304, and a lower propelling unit 305, where the propelling unit 305 is rotatably mounted to a lower surface 306 of the drive housing 304 in order to steer the vessel. The drive housing 304 encloses a transmission comprising a vertical drive shaft 310 arranged to transmit drive torque from at least one source of drive torque to a pair of forward-facing counter rotating propellers 307 on the propelling unit 305. The transmission further comprises a gear unit 313 operably connectable to an upper end of the vertical drive shaft 310, which passes directly through the gear unit 313. In FIGS. 3 and 6, a first source of drive torque is an electric motor 311 with a horizontal output shaft 312 that is operably connectable to the vertical drive shaft 310 directly through the gear unit 313. FIG. 6 shows a schematic view of the transmission for the driveline in FIG. 3. The electric motor 311 can be disconnected from the horizontal output shaft 312 and the through shaft comprising the vertical drive shaft 310 and a vertical support shaft 318 by demagnetizing the rotor. A horizontal output shaft 320 is connected to a second source of drive torque in the form of an inboard internal combustion engine (ICE) 321 located within the hull of the vessel (see FIG. 3 or 1).

[0042] The gear unit 313 comprises a set of bevel gears 315, 316, 317, 319 which are in constant driving contact with each other. Each bevel gear is associated with a respective driving or driven shaft 310, 320, 312, 318 and is switchable between a connected state and a disconnected state for transferring torque to the vertical drive shaft 210. The bevel gear 316 fixed to the horizontal output shaft 320 from the ICE 321 is switchable between a driven state and a freewheeling state by a main clutch 324 adjacent the ICE 321. The bevel gear 317 fixed to the horizontal output shaft 312 from the electric motor 311 is switchable between a driven state and a freewheeling state by magnetizing and demagnetizing the rotor of the electric motor 311. Each bevel gear 319, 315 on the vertical drive shaft 310 is controllable between its connected and disconnected states by a corresponding actuatable clutch 319′, 315′ mounted adjacent the respective bevel gear. Switching the bevel gears 319, 315 can be achieved by actuation or deactuation of a suitable controllable clutch or mechanical actuator. In the subsequent text switching is performed using wet multi-plate clutches, or lamella clutches, hereafter referred to as “clutches”. Hence, each bevel gear 319, 315 on the vertical drive shaft 310 is controllable between its connected and disconnected states by a corresponding actuatable clutch 319′, 315′ mounted adjacent the respective bevel gear.

[0043] With reference to FIG. 6, the vertical drive shaft 310 passes directly upwards through the gear unit 313 and exits as the upper supporting shaft 318. The gear unit 313 comprises an upper first bevel gear 319 and a lower second bevel gear 315 arranged on the vertical drive shaft 310. The first and second bevel gears 319, 315 are in driving connection with an intermediate third bevel gear 316 fixed to a first horizontal output shaft 320 connected to a main clutch 324 via a main clutch 324. The first and second bevel gears 319, 315 are further in driving connection with an intermediate fourth bevel gear 317 arranged on a second horizontal output shaft 312. The fourth bevel gear 317 is arranged opposite the third bevel gear 316 coaxially with the first horizontal output shaft 320. The second horizontal output shaft 312 is connected to a first source of drive torque in the form of an electric motor 311. The first horizontal output shaft 320 is connected to a second source of drive torque in the form of an inboard ICE 321 located within the hull of the vessel (see FIG. 1). The first horizontal output shaft 320 passes through a seal 322 in the transom 302 and is fixed in a vibration absorbing bushing 323 supported by the ICE output shaft. A main clutch 324 is provided between the first horizontal output shaft 320 and the ICE crankshaft to control the rotation of the first horizontal output shaft 320. The first and second bevel gears 319, 315 are freely rotatable about the supporting shaft 318 and the vertical drive shaft 310, respectively, in their disconnected state. Similarly, the third bevel gear 316 is freely rotatable with the first horizontal output shaft 320 in its disconnected state. The fourth bevel gear 317 is freely rotatable about the second horizontal output shaft 312 with the main clutch 324 in its disconnected state. The upper and lower bevel gears 319, 315 are selectably connected to the vertical drive shaft 310 in order to transmit torque from the electric motor 311 and/or the ICE 321 to the vertical drive shaft 310 and the propellers. In this way, the vertical drive shaft 310 can be operably connected to the first horizontal output shaft 320, which extends out of the drive housing 304 through the transom 302, and to the second horizontal output shaft 312.

[0044] In operation, the driveline can be operated in electric mode using the electric motor 311 for rotating the horizontal second output shaft 312 and the vertical drive shaft 310 to drive the vessel in a forward direction. In this mode, the third bevel gear 316 is allowed to rotate freely by disconnection of the main clutch 324. In the gear unit 313, the first bevel gear 319 is maintained disconnected while the second bevel gear 315 is connected to the vertical drive shaft 310 by actuation of the lower clutch 315′. At the same time, the rotor of the electric motor 311 is magnetized allowing it to be operated to transmit torque to the second horizontal output shaft 312 and the vertical drive shaft 310 via the fourth bevel gear 317 and the second bevel gear 315, in order to propel the vessel in a forward direction. Propelling the vessel in reverse direction is achieved by switching the direction of rotation of the electric motor 311.

[0045] Alternatively, the driveline can be operated in ICE mode, wherein the rotor (not shown) of the electric motor 311 is demagnetized making the second horizontal output shaft 312 freely rotatable. In the gear unit 313, the first bevel gear 319 is maintained disconnected while the second bevel gear 315 is connected to the vertical drive shaft 310 by actuation of the clutch 315′. At the same time, the third bevel gear 316 and the first horizontal output shaft 320 are operatively connected to the ICE 321 by actuation of the main clutch 324. The ICE 321 can then be operated to transmit torque to the horizontal shaft 320 and the vertical drive shaft 310 via the third bevel gear 316 and the second bevel gear 315, in order to propel the vessel in a forward direction. In order to propel the vessel in a reverse direction the main clutch 324 is deactuated. The second bevel gear 315 is then disconnected by deactuation of the clutch 315′, while the first bevel gear 319 is connected to the vertical support shaft 318 by actuation of the clutch 319′. Subsequently, the third bevel gear 316 continues to be driven the horizontal output shaft 320 by actuation of the main clutch 324. The ICE 321 can then be operated to transmit torque to the horizontal shaft 320 and the vertical drive shaft 310 via the third bevel gear 316 and the first bevel gear 319.

[0046] According to a further example, the driveline can be operated in a hybrid mode using the electric motor 311 and the ICE 321 together. In the hybrid mode, the gear unit 313 is operated in the same way as in the ICE mode described above, wherein the rotor of the electric motor 311 is magnetized so that the motor can be operated to drive the vertical output shaft 312 to assist the ICE 321. The direction of rotation of the electric motor 311 is selected to correspond with the direction of rotation of the currently connected first or second bevel gears 314, 315 selected for forward or reverse operation of the vessel using the ICE 321.

[0047] The propelling unit 305 contains a gearbox 308 operably connected to a lower end of the vertical drive shaft 310, which can be rotated as shown by the arrow Ai to drive the counter rotating propellers 307. Gearboxes for driving counter-rotating shafts of this type are well known and will not be described in further detail.

[0048] The drive housing 304 further comprises a control unit and power electronics controller (PEC) 330 for the electric motor 311. The combined control unit and power electronics controller (PEC) 330 is also used for controlling a steering arrangement 340 described below. The outer enclosure for the drive housing 304 provides a thermal mass to absorb the heat generated by the electric motor 311 and the PEC 330. In operation, the drive housing 304 is immersed in water and the water provides effective convection cooling. The electric motor 311 is connected to the PEC 330, which supplies current to the electric motor 311 from an inboard energy storage (not shown). Control means such as a throttle and a steering means (not shown) are provided at an operator station on-board the vessel.

[0049] The propelling unit 305 is arranged to be rotatable relative to the lower surface 306 of the drive housing by a steering arrangement 340 in order to steer the vessel. The steering arrangement 340 is located in the drive housing comprises a steering system with a control unit and a steering drive unit for rotating the propelling unit about its vertical axis. The steering drive unit can comprise an electric motor. The steering drive unit drives a steering transmission comprising a pinon gear that drives a gear fixed to the propelling unit 305 about the central axis X of the vertical drive shaft 310 as indicated by the arrow A2.

[0050] The drive housing 304 in FIG. 3 further comprises a coolant and lubricant circuit of the same type as described with reference to FIG. 2 above.

[0051] FIG. 4 shows a schematic side view of a driveline according to a third example. FIG. 4 shows the drive unit 403 mounted to a transom 402 of a marine vessel (see FIG. 1). The drive unit 403 comprises an upper drive housing 404, and a lower propelling unit 405, where the propelling unit 405 is rotatably mounted to a lower surface 406 of the drive housing 404 in order to steer the vessel. The drive housing 404 encloses a transmission comprising a vertical drive shaft 410 arranged to transmit drive torque from at least one source of drive torque to a pair of forward-facing counter rotating propellers 407 on the propelling unit 405. The transmission further comprises a gear unit 413 operably connected to an upper end of the vertical drive shaft 410. In FIGS. 4 and 7, one first source of drive torque is an electric motor 411 with a vertical output shaft 412 that is operably connectable to the vertical drive shaft 410 directly through the gear unit 413. A further first source of drive torque is a second electric motor 417 with a horizontal output shaft 418 that is operably connectable to the vertical drive shaft 410 via the gear unit 413.

[0052] FIG. 7 shows a schematic view of the transmission for the driveline in FIG. 4. The electric motors 411, 417 can be disconnected from their respective shaft 412, 418 and the through shaft comprising the vertical drive shaft 410 by demagnetizing their respective rotors. A horizontal output shaft 320 is connected to a second source of drive torque in the form of an inboard ICE 321 located within the hull of the vessel (see FIGS. 4 and 1).

[0053] The gear unit 413 comprises a set of bevel gears 414, 415, 416, 419 which are in constant driving contact with each other. Each bevel gear is associated with a respective driving or driven shaft 412, 410, 420, 418 and is switchable between a connected state and a disconnected state for transferring torque to the vertical drive shaft 410. The bevel gear 416 fixed to the horizontal output shaft 420 from the ICE 421 is switchable between a driven state and a freewheeling state by a main clutch 424 adjacent the ICE 421. The bevel gear 419 fixed to the horizontal output shaft 418 from the electric motor 417 is switchable between a driven state and a freewheeling state by magnetizing and demagnetizing the rotor of the electric motor 417. Each bevel gear 414, 415 on the vertical drive shaft 410 is controllable between its connected and disconnected states by a corresponding actuatable clutch 414′, 415′ mounted adjacent the respective bevel gear. Switching the bevel gears 414, 415 can be achieved by actuation or deactuation of a suitable controllable clutch or mechanical actuator. In the subsequent text switching is performed using wet multi-plate clutches, or lamella clutches, hereafter referred to as “clutches”. Hence, each bevel gear 414, 415 is controllable between its connected and disconnected states by a corresponding actuatable clutch 414′, 415′ mounted adjacent the respective bevel gear.

[0054] With reference to FIG. 7, the vertical output shaft 412 of the electric motor 411 passes directly through the gear unit 413. The gear unit 413 comprises an upper first bevel gear 414 arranged on the vertical output shaft 412 and a lower second bevel gear 415 arranged on the vertical drive shaft 410. The first and second bevel gears 414, 415 are in driving connection with an intermediate third bevel gear 416 arranged on a first horizontal output shaft 420 connected to a main clutch 424 via a main clutch 424. The first and second bevel gears 414, 415 are further in driving connection with an intermediate fourth bevel gear 419 arranged on a second horizontal output shaft 418. The fourth bevel gear 419 is arranged opposite the third bevel gear 416 coaxially with the first horizontal output shaft 420. The second horizontal output shaft 418 is connected to an optional further source of drive torque in the form of a second electric motor 417. The first horizontal output shaft 420 is connected to a second source of drive torque in the form of an inboard ICE 421 located within the hull of the vessel (see FIG. 1). The first horizontal output shaft 420 passes through a seal 422 in the transom 402 and is fixed in a vibration absorbing bushing 423 supported by the ICE output shaft. A clutch 424 is provided between the first horizontal output shaft 420 and the ICE crankshaft to control the rotation of the first horizontal output shaft 420. The first and second bevel gears 414, 415 are freely rotatable about the vertical output shaft 412 and the vertical drive shaft 410, respectively, in their disconnected state. Similarly, the third bevel gear 416 is freely rotatable about the first horizontal output shaft 420 in its disconnected state. The fourth bevel gear 419 is freely rotatable about the second horizontal output shaft 418 in its disconnected state. The upper and lower bevel gears 414, 415 are selectably connected to their respective shaft in order to transmit torque from the ICE 421 and/or from the second electric motor 417 to the vertical drive shaft 410 and the propellers. In this way, the vertical drive shaft 410 can be operably connected to the first horizontal output shaft 420 which extends out of the drive housing 404 through the transom 402.

[0055] In operation, the driveline can be operated in electric mode using the electric motor 411 rotating the output shaft 412 and the vertical drive shaft 410 directly to drive the vessel in a forward direction, as described for FIGS. 4 and 6. The second electric motor 417 can be operated together with, or instead of the electric motor 411 in electric mode. In this mode, the third bevel gear 416 is allowed to rotate freely by disconnection of the main clutch 424. This is achieved by maintaining the first bevel gear 414 disconnected. At the same time, or alternatively, the fourth bevel gear 419 is connected to the second horizontal output shaft 418 by actuation of the clutch 419′ and the second bevel gear 415 is connected to the vertical drive shaft 410 by actuation of the clutch 415′. Propelling the vessel in reverse direction is achieved by switching the direction of rotation of the electric motors 411, 417. The provision of two electric motors provides a degree of redundancy in case one motor should malfunction.

[0056] Alternatively, the driveline can be operated in ICE mode, wherein the rotors (not shown) of the electric motors 411, 417 are demagnetized making the vertical output shaft 412 and the second horizontal output shaft 418 freely rotatable. In the gear unit 413, the first bevel gear 414 is maintained disconnected while the second bevel gear 415 is connected to the vertical drive shaft 410 by actuation of the clutch 415′. At the same time, the third bevel gear 416 and the first horizontal output shaft 420 are operatively connected to the ICE 421 by actuation of the main clutch 424. The ICE 421 can then be operated to transmit torque to the horizontal shaft 420 and the vertical drive shaft 410 via the third bevel gear 416 and the second bevel gear 415, in order to propel the vessel in a forward direction. In order to propel the vessel in a reverse direction the main clutch 424 is deactuated. The second bevel gear 415 is then disconnected by deactuation of the clutch 415′, while the first bevel gear 414 is connected to the vertical output shaft 412 by actuation of the clutch 414′. Subsequently, the third bevel gear 416 continues to be driven by the horizontal output shaft 420 by actuation of the main clutch 424. The ICE 421 can then be operated to transmit torque to the horizontal shaft 420 and the vertical drive shaft 410 via the third bevel gear 416 and the first bevel gear 414.

[0057] According to a further example, the driveline can be operated in a hybrid mode using the electric motors 411, 417 and the ICE 421 together. In the hybrid mode, the gear unit 413 is operated in the same way as in the ICE mode described above, wherein the rotor of the electric motor 411 and/or the electric motor 417 is magnetized so that the motors can be operated to drive the vertical output shaft 412 to assist the ICE 421. The direction of rotation of the electric motors 411, 417 is selected to correspond with the direction of rotation of the currently connected first or second bevel gears 414, 415 selected for forward or reverse operation of the vessel using the ICE 421.

[0058] The propelling unit 405 contains a gearbox 408 operably connected to a lower end of the vertical drive shaft 410 , which can be rotated as shown by the arrow A.sub.l to drive the counter rotating propellers 407. Gearboxes for driving counter-rotating shafts of this type are well known and will not be described in further detail.

[0059] The drive housing 404 further comprises a control unit and power electronics controller (PEC) 430 for the electric motor 411. The combined control unit and power electronics controller (PEC) 430 is also used for controlling a steering arrangement 440 described below. The outer enclosure for the drive housing 404 provides a thermal mass to absorb the heat generated by the electric motor 411 and the PEC 430. In operation, the drive housing 404 is immersed in water and the water provides effective convection cooling. The electric motor 411 is connected to the PEC 430, which supplies current to the electric motor 411 from an inboard energy storage (not shown). Control means such as a throttle and a steering means (not shown) are provided at an operator station on-board the vessel.

[0060] The propelling unit 405 is arranged to be rotatable relative to the lower surface 406 of the drive housing by a steering arrangement 440 in order to steer the vessel. The steering arrangement 440 is located in the drive housing comprises a steering system with a control unit and a steering drive unit for rotating the propelling unit about its vertical axis. The steering drive unit can comprise an electric motor. The steering drive unit drives a steering transmission comprising a pinon gear that drives a gear fixed to the propelling unit 405 about the central axis X of the vertical drive shaft 410 as indicated by the arrow A.sub.2.

[0061] The drive housing 404 in FIG. 4 further comprises a coolant and lubricant circuit of the same type as described with reference to FIG. 2 above.

[0062] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.