Power unit, power generation assembly and propulsion system for a ship

Abstract

The power unit (10) for a controllable pitch propeller (1) of a ship comprises a body (11) that is configured to be attached in a rotationally fixed manner to a propeller shaft (4) of a ship or to an extension of a gearbox shaft that is coaxial with the propeller shaft (4), and a pitch angle actuation pump (12) for pressurizing hydraulic fluid for actuating pitch angle actuation means (31, 32) of the propeller (1).

Description

[0001] Power unit, power generation assembly and propulsion system for a ship

[0002] Technical field of the invention

[0003] The present invention concerns a power unit for a controllable pitch propeller of a ship. The invention further concerns a power generation assembly and a propulsion system for a ship.

[0004] Background of the invention

[0005] The main parameters affecting the thrust force delivered by a propeller behind a ship at a given ship speed are the diameter of the propeller, the number of blades of the propeller, the rotation speed of the propeller, and the pitch of the propeller. The diameter of the propeller and the number of blades are always fixed for any given ship. If also the pitch of the propeller is fixed, the thrust force can be changed only be changing the rotation speed of the propeller. The propellers are often driven by an internal combustion engine, such as a two-stroke or four-stroke piston engine. Alternatively, the propellers can be driven by an electric motor. Especially in case of a four-stroke engine, a gearbox is typically arranged between the engine and the propeller to allow both the engine and the propeller to rotate at suitable speeds. However, the gearboxes typically have a fixed gear ratio, although in some applications a two-speed gearbox may be used. With a single-speed gearbox and a fixed-pitch propeller, the thrust force can be changed only by changing the rotation speed of the engine. As the internal combustion engines always have a certain rotation speed range providing the best fuel efficiency, operating outside of this range reduces the efficiency of the engine.

[0006] A controllable pitch propeller allows changing of the pitch angle of the propeller. In a controllable pitch propeller the propeller blades are attached to a propeller hub, which enables changing of the pitch angle during normal operation of the ship. A further control parameter for controlling the thrust force of the propeller is thus provided. This allows the engine driving the propeller to be operated in a more optimal rotating speed range. A controllable pitch propeller also improves the maneuvering characteristics of the ship and enables adapting the pitch angle to changing environmental conditions, such as waves. Different control strategies can be developed for the pitch angle and the engine to optimize the overall efficiency and operation of the propulsion system. Controllable pitch propellers can be and are currently used in many kinds of ships, such as ferries, tugs and anchor handlers, trawlers, dredgers, general cargo vessels and frigates and other naval vessels.

[0007] The diameter of the propeller of a large ship can be several meters and the propeller blades can cover a large area. Changing of the pitch angle of a propeller blade thus requires a lot of torque that is applied via an actuating system. Hydraulic systems can provide sufficient torque for changing the pitch angle. However, supplying of pressurized hydraulic fluid to a propeller that is attached to a rotating shaft is challenging. If the propeller shaft of the ship is arranged in a torque transmission connection with the engine via a gearbox, an oil delivery box can be arranged on an extension of a gearbox shaft on the engine side of the gearbox coaxially with the propeller shaft. The oil delivery box comprises a stator attached to the ship and a rotor that is attached to one end of the gearbox shaft. Pressurized hydraulic fluid is delivered from a hydraulic pump to the stator, from which it can flow into the rotor. The hydraulic fluid is conducted via hydraulic fluid pipes through the gearbox and the propeller shaft to the propeller. If there is no gearbox between the engine and the propeller shaft, an oil delivery box can be arranged around the propeller shaft. The hydraulic fluid is conducted from the stationary part of the oil delivery box into radial bores of the propeller shaft and into hydraulic fluid pipes arranged within the propeller shaft.

[0008] Regardless of whether the hydraulic fluid is supplied to the hub of the propeller via a separate rotor attached to the shaft of the gearbox or directly via a main torque transmitting shaft, there is always some leakage between the rotating and stationary part of the fluid supply arrangement. This is due to the combination of the level of hydraulic pressure and circumferential speed of the ro- tor / stator interface, limiting possible sealing solutions. To prevent excessive leakage, the pressure of the hydraulic fluid needs to be limited. If the propeller diameter and propeller blade area are large, a large torque is needed for changing the pitch angle, and the piston diameter of the pitch angle changing arrangement in the hub of the propeller needs to be increased to achieve the required torque.

[0009] When a controllable pitch propeller is used, there is a need to monitor the propeller blade pitch angle to ensure safe operation of the controllable pitch propeller. When using electrical sensors directly in the rotating parts for monitoring the pitch angle, electrical power is needed in the rotating parts for powering the sensors. Supplying the electrical power to the rotating parts is challenging. One way to supply electrical power from a stationary part to a rotating part is to use an electrically conductive ring and electrically conductive brushes arranged in contact with the ring. A drawback of this solution is that the brushes wear and thus need regular maintenance. Another option is the use of inductive power supply, which is contactless. A problem with inductive power supply is that the rotation speed of the propeller shaft is relatively low and not optimal for inductive power supply. Also, due to the large thrust forces transmitted by the propeller shaft, movements of the propeller shaft can be significant and a relatively large gap is needed between the rotating and stationary parts of the inductive power supply, which limits the magnitude of electric power that can be transmitted inductively.

[0010] Due to the challenges of the electrical power supply, propeller blade pitch angles have been monitored using an electrical sensor arranged in the stationary part of the oil delivery box. The sensor monitors the position of a component attached to a hydraulic fluid pipe supplying hydraulic fluid to the hub of the propeller. When the oil delivery box is arranged around a main torque transmitting shaft, to accommodate the component, the propeller shaft is normally provided with a radial slot, which weakens the propeller shaft.

[0011] Summary of the invention

[0012] An object of the invention is to provide for a controllable pitch propeller of a ship a power unit that solves at least some of the problems of prior art propulsion systems. Another object of the invention is to provide a power generation assembly comprising such a power unit. A further object of the invention is to provide a propulsion system comprising such a power unit. The invention is defined in the independent claims.

[0013] The power unit according to the invention comprises a body that is configured to be attached in a rotationally fixed manner to a propeller shaft of a ship or to an extension of a gearbox shaft that is coaxial with the propeller shaft. According to one aspect of the invention, the power unit comprises a pitch angle actuation pump for pressurizing hydraulic fluid for actuating pitch angle actuation means of the propeller. According to another aspect of the invention, the power unit comprises an electric generator, which is provided with a torque trans- mission element that is configured to be arranged in a mechanical torque transmission connection with a non-rotating drive element so that rotating movement of the propeller shaft or the gearbox shaft drives the electric generator. The power unit can comprise both the pitch angle actuation pump and the electric generator or one of those.

[0014] The power unit is thus configured to rotate coaxially with the propeller shaft and it can be self-contained in regard to hydraulic power and / or electricity. The problems relating to the supply of pressurized hydraulic fluid and / or electricity to the rotating propeller shaft can thus be avoided.

[0015] According to an embodiment of the invention, the pitch angle actuation pump is provided with a torque transmission element that is configured to be arranged in a mechanical torque transmission connection with a non-rotating drive element so that rotating movement of the propeller shaft or the gearbox shaft drives the pitch angle actuation pump. The torque transmission element can be a gearwheel. By means of the torque transmission element and the drive element the pitch angle actuation pump can be powered by the rotating movement of the propeller shaft or the gearbox shaft. However, the pitch angle actuation pump could also be electrically powered.

[0016] According to an embodiment of the invention, the pitch angle actuation pump is a variable displacement pump. This allows simple control of the flow of hydraulic fluid to the pitch angle actuation means.

[0017] According to an embodiment of the invention, the power unit comprises a manifold for receiving pressurized hydraulic fluid from the pitch angle actuation pump and for supplying hydraulic fluid to the pitch angle actuation pump.

[0018] According to an embodiment of the invention, the power unit comprises a hydraulic fluid tank for storing the hydraulic fluid. All the hydraulic fluid needed for the operation of the pitch angle actuation means can thus be stored in the power unit and no external fluid supply is needed.

[0019] According to an embodiment of the invention, the power unit comprises an electronic control unit for controlling the operation of the pitch angle actuation pump. The electronic control unit can be configured to communicate, for example via wireless communication means, with a pitch angle control unit located outside of the power unit. According to an embodiment of the invention, the power unit comprises at least two pitch angle actuation pumps. Two pitch angle actuation pumps provide redundancy for the pitch angle actuation system.

[0020] According to an embodiment of the invention, the power unit comprises a hydraulic fluid inlet that is configured to allow supply of pressurized hydraulic fluid into the power unit and further to the pitch angle actuation means when the power unit is stationary to allow emergency operation of the pitch angle actuation means. This allows changing of the pitch angle even when the pitch angle actuation pumps are not operating.

[0021] According to an embodiment of the invention, the torque transmission element of the electric generator is a gearwheel.

[0022] According to an embodiment of the invention, the power unit comprises a hub lubrication pump for pressurizing lubrication oil for lubricating parts of a propeller hub. By providing the power unit with a hub lubrication pump, even supply of lubrication oil to a rotating propeller shaft can be avoided.

[0023] According to an embodiment of the invention, the power unit comprises a lubrication oil tank for storing the lubrication oil.

[0024] The power generation assembly according to the invention comprises a power unit defined above and a drive element that is configured to be attached to a stationary structure of the ship in a non-rotating manner and configured to be arranged in a mechanical torque transmission connection with a pitch angle actuation pump, electric generator and / or another device of the power unit so that rotating movement of a propeller shaft or a gearbox shaft of the ship drives said pump, said electric generator and / or said other device.

[0025] The propulsion system according to the invention comprises a propeller shaft, a controllable pitch propeller attached to the propeller shaft, and a power unit defined above attached in a rotationally fixed manner to the propeller shaft or to an extension of a gearbox shaft that is coaxial with the propeller shaft.

[0026] According to an embodiment of the invention, the propulsion system comprises a drive element that is attached to a stationary structure of the ship in a nonrotating manner and arranged in a mechanical torque transmission connection with a pitch angle actuation pump, electric generator and / or another device of the power unit so that rotating movement of the propeller shaft or the gearbox shaft of the ship drives said pump, said electric generator and / or said other device.

[0027] According to an embodiment of the invention, the drive element is a gearwheel.

[0028] According to an embodiment of the invention, the drive element is arranged around the propeller shaft.

[0029] According to an embodiment of the invention, the propulsion system is provided with at least one support rod having a first end attached to the drive element and a second end that is attached to a stationary structure of the ship to prevent rotation of the drive element.

[0030] According to an embodiment of the invention, the propulsion system comprises hydraulically operable pitch angle actuation means.

[0031] According to an embodiment of the invention, the power unit comprises a hydraulic fluid inlet that is configured to allow supply of pressurized hydraulic fluid into the power unit and further to the pitch angle actuation means when the power unit is stationary to allow emergency operation of the pitch angle actuation means, and the propulsion system comprises a hydraulic unit for supplying pressurized hydraulic fluid into the power unit via the hydraulic fluid inlet.

[0032] According to an embodiment of the invention, the hydraulic unit comprises a hydraulic pump and / or a pressure accumulator.

[0033] According to an embodiment of the invention, the propulsion system comprises a pitch angle sensor.

[0034] According to an embodiment of the invention, the pitch angle sensor is connected to wireless communication means that are configured to communicate with a pitch angle control unit.

[0035] Brief description of the drawings

[0036] Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which

[0037] Fig. 1 shows a propulsion system of a ship, Fig. 2 shows a propeller shaft and a power unit according to an embodiment of the invention,

[0038] Fig. 3 shows an enlarged view of the power unit of figure 2,

[0039] Fig. 4 shows a cross-sectional view of the power unit of figures 2 and 3,

[0040] Fig. 5 shows a propeller hub,

[0041] Fig. 6 shows a simplified hydraulic diagram of a pitch angle actuation system, and

[0042] Fig. 7 shows as a block diagram parts of a propulsion system according to an embodiment of the invention.

[0043] Detailed description of embodiments of the invention

[0044] Figure 1 shows schematically a simplified view of a propulsion system according to an embodiment of the invention. The propulsion system produces thrust force for a ship. The ship can be any kind of a ship, such as a ferry, tug or anchor handler, trawler, dredger, general cargo vessel, or frigate or other naval vessel.

[0045] The propulsion system comprises an internal combustion engine 6. The engine 6 can be a piston engine. The engine can be either a four-stroke engine or a two-stroke engine. The propulsion system comprises a propeller 1 , which is a controllable pitch propeller. The propeller 1 comprises two or more propeller blades 2, which are rotatably attached to a propeller hub 3. The number of propeller blades 2 can be, for instance, 3-7. In the embodiments of figures 1 to 5, the propeller 1 comprises four propeller blades 2.

[0046] The rotating motion of the engine 6 is transmitted to the propeller 1 by means of a propeller shaft 4. In the embodiment of figure 1 , the propulsion system is provided with a gearbox 5. The term “propeller shaft” refers here to the whole shaft line between the propeller 1 and the gearbox 5. If the propulsion system did not comprise a gearbox, the propeller shaft would be the whole shaft line between the propeller 1 and the engine 6. The propeller shaft 4 can comprise two or more parts connected one after another. The gearbox 5 has at least one input shaft that is coupled to the crankshaft of the engine 6. The gearbox 5 comprises an output shaft that is coupled to the propeller shaft 4. The gearbox 5 is not necessary, but the propeller shaft 4 could also be coupled directly to the crankshaft of the engine 6. The gearbox 5 can have a fixed gear ratio. Alternatively, the gearbox 5 could be for example a two-speed gearbox. The gearbox 5 could have two input shafts to allow the propeller shaft 4 to be driven by two engines 6.

[0047] The propeller hub 3 comprises a rotatable flange 32 for each propeller blade 2. An example of a propeller hub 3 is shown in figure 5. By rotating the flange 32, the propeller blade 2 rotates about a rotation axis that this perpendicular to the rotation axis of the propeller shaft 4. The propeller blades 2 are not freely rotating about the rotation axis but can turn over a certain angle to allow the pitch angle of the propeller 1 to be adjusted within a predetermined range.

[0048] As the propeller blades 2 are rotated about the rotation axis of the respective flanges 32, the pitch angle of the propeller 1 changes. The flanges 32 are rotated by means of a piston 31 that is arranged inside the propeller hub 3. The piston 31 has a first piston surface 31 A and a second piston surface 31 B. By applying hydraulic pressure onto the first piston surface 31 A or the second piston surface 31 B, the piston 31 is moved either towards the astern or towards the bow of the ship and the pitch angle of the propeller 1 is changed. The piston 31 and the flanges 32 form pitch angle actuation means of the propeller 1 . The pitch angle actuation means could be implemented also in some alternative way. For instance, the pitch angle actuation means could comprise separate pistons for each of the propeller blades 2 and / or for different rotation directions of the propeller blades 2.

[0049] The larger the propeller blades 2 are, the greater force is needed to change the pitch angle. The force can be increased either by raising the hydraulic pressure applied onto the piston surfaces 31 A, 31 B of the piston 31 or by making the piston surfaces larger. In prior art solutions, the pressurized hydraulic fluid needed for moving the piston has been introduced into the propeller shaft via an oil delivery box comprising a rotating rotor and a stationary stator. The available hydraulic pressure has been limited by the capability of the sealing arrangement between the stator and the rotor.

[0050] The power unit 10 according to the invention solves problems encountered in the prior art propulsion systems. Different views of a power unit according to an embodiment of the invention are shown in figures 2 to 4. In the embodiment of figures 2 to 4, the power unit 10 comprises a body 11 that is configured to be attached in a rotationally fixed manner to the propeller shaft 4 of a ship. The power unit 10 thus rotates together with the propeller shaft 4. The power unit 10 is arranged apart from the propeller hub 3. The power unit 10 can be located close to the bow end of the propeller shaft 4.

[0051] Instead of attaching the power unit 10 to the propeller shaft 4, the power unit 10 could be attached to an extension of a gearbox shaft that is coaxial with the propeller shaft 4. The power unit 10 could thus be attached to an extension of the output shaft of the gearbox 5 between the gearbox and the engine 6. This could be beneficial in ships having a relatively short propeller shaft 4 and thus little space between the gearbox and the astern of the ship.

[0052] According to one aspect of the invention, the power unit 10 comprises a pitch angle actuation pump 12 for pressurizing hydraulic fluid for actuating the pitch angle actuation means 31 , 32 of the propeller 1 . The high pressure needed for rotating the propeller blades 2 for adjusting the pitch angle can thus be produced by one or more pumps that rotate with the propeller shaft 4 or with a coaxial shaft rotating synchronically with the propeller shaft 4. As the high pressure fluid does not need to be supplied from a non-rotating part to a rotating part, the connections of the hydraulic circuit are simpler to seal. This reduces leakages and also allows using higher pressures in the pitch angle actuation system. As higher pressures can be used, the piston 31 of the propeller hub 3 can have smaller dimensions. A relatively small propeller hub 3 can thus be used even for propellers 1 having large propeller blades 2. A certain propeller hub 3 could thus be used for larger propellers than before.

[0053] In the embodiments of figures 2 to 4 and 5, the power unit 10 comprises two pitch angle actuation pumps 12. This provides redundancy and allows changing of the pitch angle even in case one of the pitch angle actuation pumps 12 fails.

[0054] In the embodiment of figures 2 to 4, the propulsion system is provided with a gearwheel 21 that is arranged around the propeller shaft 4 and attached to a stationary structure of the ship in a non-rotating manner. The gearwheel 21 is supported around the propeller shaft 4 by means of a bearing 25. The bearing 25 can be either a rolling bearing or sliding bearing. In the embodiment of figures 2 to 4, the gearwheel 21 is attached to the ship by means of two support rods 22. The support rods 22 prevent the gearwheel 21 from rotating with the propeller shaft 4, but allow small movements of the gearwheel 21 in the axial direction of the propeller shaft 4.

[0055] Each pitch angle actuation pump 12 is provided with a gearwheel 13 that is arranged in a mechanical torque transmission connection with the non-rotating gearwheel 21 . Rotating movement of the propeller shaft 4 or the gearbox shaft thus drives the pitch angle actuation pumps 12. External power supply is thus not needed for driving the pitch angle actuation pumps 12. The gearwheels 13, 21 provide a simple and reliable way of driving the pitch angle actuation pumps 12, but also other means could be used for driving the pumps 12. For instance, friction wheels could be used as torque transmitting elements of the pitch angle actuation pumps 12, or the power unit 10 could be provided with electric motors for driving the pitch angle actuation pumps 12. Alternatively, a belt or chain could be used for driving the pitch angle actuation pumps 12.

[0056] If the power unit 10 was arranged between the gearbox 5 and the engine 6, the pitch angle actuation pumps 12 could be driven in a similar way as in the embodiments of the figures. The gearwheel 21 for driving the gearwheels 13 of the pitch angle actuation pumps 12 could thus be arranged around an extension of the output shaft of the gearbox 5. However, the space on the front side of the gearbox 5 may be too small for accommodating a driving gearwheel that is large enough for reaching a sufficient rotation speed of the pitch angle actuation pumps 12. In that case, instead of using a non-rotating driving gearwheel 21 , the driving gearwheel 21 could be rotated around the extension of the output shaft of the gearbox 5 at a suitable rotation speed.

[0057] In the embodiment of figures 2 to 4, the power unit 10 comprises a manifold 18 for receiving pressurized hydraulic fluid from the pitch angle actuation pumps 12 and for supplying hydraulic fluid to the pitch angle actuation pumps 12. The power unit 10 comprises a hydraulic fluid tank 19 for storing the hydraulic fluid. Both the manifold 18 and the hydraulic fluid tank 19 rotate with the propeller shaft 4. However, the hydraulic fluid tank 19 could also be stationary. The hydraulic fluid tank 19 does not need to be arranged around the propeller shaft 4, but it could be arranged apart from the power unit 10 and the propeller shaft 4. In that case hydraulic fluid would need to be supplied from a stationary part to a rotating part. However, the hydraulic fluid could be supplied to the pitch angle actuation pumps 12 at a relatively low pressure. The pressure could be, for instance, less than 10 bar. With low pressures, the sealing of the connection between the stationary part and the rotating part would be much simpler than in case the pressure needed for changing the pitch angle is produced by stationary hydraulic pumps. The power unit 10 would thus provide significant benefits even without an integrated hydraulic fluid tank 19.

[0058] The pitch angle actuation pumps 12 can be variable displacement pumps. The power unit 10 can comprise an electronic control unit 23 for controlling the operation of the pitch angle actuation pumps 12.

[0059] In the embodiments of the figures, the pitch angle actuation pumps 12 are driven by the rotating motion of the propeller shaft 4. Consequently, when the propeller shaft 4 is not rotating, no hydraulic power is produced and the pitch angle cannot be changed. For allowing changing of the pitch angle also in case the propeller shaft 4 is not rotating, the power unit 10 can comprise a hydraulic fluid inlet that is configured to allow supply of pressurized hydraulic fluid into the power unit 10 and further to the pitch angle actuation means 31 , 32 when the power unit 10 is stationary to allow emergency operation of the pitch angle actuation means 31 , 32. The propulsion system can comprise a hydraulic unit that can be connected to the hydraulic fluid inlet and comprises a hydraulic pump and / or a pressure accumulator. The hydraulic unit can be a stationary unit located apart from the propeller shaft 4.

[0060] According to one aspect of the invention, the power unit 10 comprises an electric generator 16. The electric generator 16 is provided with a torque transmission element 17 that is arranged in a mechanical torque transmission connection with a non-rotating drive element 21 . In the embodiment of the figures 2 to

[0061] 4, the torque transmission element 17 is a gearwheel and the non-rotating drive element 21 is the same gearwheel that is used for driving the pitch angle actuation pumps 12. The rotating movement of the propeller shaft 4 thus drives the electric generator 16. Instead of using the same gearwheel 21 for driving the pitch angle actuation pumps 12 and the electric generator 16, the propulsion system could be provided with a separate driving gearwheel for the electric generator 16. As with the pitch angle actuation pumps 16, some other means, such as a belt or chain, could be used for driving the electric generator 16. If the power unit 10 was arranged between the engine 6 and the gearbox

[0062] 5, the electric generator 16 could be driven in a similar way as the pitch angle actuation pumps 12. In the embodiment of figures 2 to 4, the power unit 10 comprises two electric generators 16.

[0063] The electric generators 16 can produce electric power for any electrical devices rotating with the propeller shaft 4. There is thus no need to have electrically conductive brushes or inductive power transmission between stationary and rotating parts. The electrical devices powered by the electric generators 16 can include, for instance, different sensors, communication means and control devices. The electric generators 16 could power even electric motors used for driving the pitch angle actuation pumps 12. Although it is beneficial to provide the power unit 10 with the electric generators 16, that is not necessary. A power unit 10 provided with the pitch angle actuation pumps 12 would provide many benefits even without the electric generators 16. Similarly, a power unit 10 with the electric generators 16 would provide many benefits even without the pitch angle actuation pumps 12.

[0064] In the embodiments of the figures, the power unit 10 comprises a hub lubrication pump 14 for pressurizing lubrication oil for lubricating parts of a propeller hub 3. The power unit 10 also comprises a lubrication oil tank 20 for storing the lubrication oil. The hub lubrication pump 14 and the lubrication oil tank 20 are part of a hub lubrication system. The hub lubrication system is independent from the pitch angle actuation system. The hub lubrication pump 14 and lubrication oil tank 20 arranged in the power unit 10 provide similar benefits as the parts of the pitch angle actuation system arranged in the power unit 10 by removing the need to supply pressurized liquid from a stationary part to a rotating part.

[0065] Parts of the power unit 10 can be attached to the body 11 of the power unit 10 either directly or indirectly. However, some parts of the power unit 10 could also be attached directly to the propeller shaft 4.

[0066] Figure 6 shows the pitch angle actuation system as a simplified hydraulic diagram. The two pitch angle actuation pumps 12 are arranged in parallel and pressurize hydraulic fluid that is supplied to the pumps 12 from the tank 19. The pitch angle actuation system is provided with a flow control valve 26. The flow control valve 26 is used for selecting whether hydraulic pressure is applied onto the first piston surface 31 A or the second piston surface 31 B of the piston 31 in the propeller hub 3. The flow control valve 26 can be arranged in the power unit 10. The flow control valve 26 can be either electrically or hydraulically controlled valve. The pressurized hydraulic fluid is supplied to the piston 31 via pipes that are arranged within the propeller shaft.

[0067] Figure 7 shows part of the propulsion system according to an embodiment of the invention as a block diagram. The electronic control unit 23 of the power unit 10 can form a local control unit that controls the operation of the pitch angle actuation pumps 12, the lubrication pump 14 and the flow control valve 26. The electronic control unit 23 can be powered by the electric generators 16. The power unit 10 could comprise a battery that powers the electronic control unit 23 when the propeller shaft 4 is not rotating and the electric generators 16 do not generate power. The propulsion system can comprise a remote control unit 29, and the electronic control unit 23 can be configured to communicate with the remote control unit 29.

[0068] The power unit 10 can comprise wireless communication means 28 for communicating with the remote control unit 29. The wireless communication means 28 can be integrated with the electronic control unit 23 of the power unit 10 or the wireless communication means can comprise a separate transceiver 28.

[0069] The propulsion system can comprise a pitch angle sensor 27 that is configured to monitor the pitch angle of the propeller 1 . The pitch angle sensor 27 could be located in the propeller hub 3, propeller shaft 4 or power unit 10. The pitch angle sensor 27 can be configured to communicate with the electronic control unit 23 of the power unit 10. Alternatively, the pitch angle sensor 27 could communicate directly with the remote control unit 29. The pitch angle sensor 27 could comprise an integrated wireless transmitter or it could be connected to separate wireless communication means that are configured to communicate with the remote control unit 29.

Claims

Claims:1 . A power unit (10) for a controllable pitch propeller (1 ) of a ship, the power unit (10) comprising a body (11 ) that is configured to be attached in a rotationally fixed manner to a propeller shaft (4) of a ship or to an extension of a gearbox shaft that is coaxial with the propeller shaft (4), and a pitch angle actuation pump (12) for pressurizing hydraulic fluid for actuating pitch angle actuation means (31 , 32) of the propeller (1 ).

2. The power unit (10) according to claim 1 , wherein the pitch angle actuation pump (12) is provided with a torque transmission element (13) that is configured to be arranged in a mechanical torque transmission connection with a non-rotating drive element (21 ) so that rotating movement of the propeller shaft (4) or the gearbox shaft drives the pitch angle actuation pump (12).

3. The power unit (10) according to claim 2, wherein the torque transmission element (13) is a gearwheel.

4. The power unit (10) according to any of claims 1 to 3, wherein the pitch angle actuation pump (12) is a variable displacement pump.

5. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises a manifold (18) for receiving pressurized hydraulic fluid from the pitch angle actuation pump (12) and for supplying hydraulic fluid to the pitch angle actuation pump (12).

6. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises a hydraulic fluid tank (19) for storing the hydraulic fluid.

7. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises an electronic control unit (23) for controlling the operation of the pitch angle actuation pump (12).

8. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises at least two pitch angle actuation pumps9. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises a hydraulic fluid inlet that is configured to allow supply of pressurized hydraulic fluid into the power unit (10) and further to the pitch angle actuation means (31 , 32) when the power unit (10) is stationary to allow emergency operation of the pitch angle actuation means (31 , 32).

10. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises an electric generator (16), which is provided with a torque transmission element (17) that is configured to be arranged in a mechanical torque transmission connection with a non-rotating drive element (21 ) so that rotating movement of the propeller shaft (4) or the gearbox shaft drives the electric generator (16).

11. A power unit (10) for a controllable pitch propeller (1 ) of a ship, the power unit (10) comprising a body (11 ) that is configured to be attached in a rotationally fixed manner to a propeller shaft (4) of a ship or to an extension of a gearbox shaft that is coaxial with the propeller shaft (4), and an electric generator (16), which is provided with a torque transmission element (17) that is configured to be arranged in a mechanical torque transmission connection with a non-rotating drive element (21 ) so that rotating movement of the propeller shaft (4) or the gearbox shaft drives the electric generator (16).

12. The power unit (10) according to claim 10 or 11 , wherein the torque transmission element (17) of the electric generator (16) is a gearwheel.

13. The power unit (10) according to any of the preceding claims, wherein the power unit (10) comprises a hub lubrication pump (14) for pressurizing lubrication oil for lubricating parts of a propeller hub (3).

14. The power unit (10) according to claim 13, wherein the power unit (10) comprises a lubrication oil tank (20) for storing the lubrication oil.

15. A power generation assembly comprising a power unit (10) according to any of the preceding claims and a drive element (21 ) that is configured to be attached to a stationary structure of the ship in a non-rotating manner and configured to be arranged in a mechanical torque transmission connection with a pitch angle actuation pump (12), electric generator (16)and / or another device (14) of the power unit (10) so that rotating movement of a propeller shaft (4) or a gearbox shaft of the ship drives said pump (12), said electric generator (16) and / or said other device (14).

16. A propulsion system for a ship, the propulsion system comprising a propeller shaft (4), a controllable pitch propeller (1 ) attached to the propeller shaft (4), and a power unit (10) according to any of claims 1 to 14 attached in a rotationally fixed manner to the propeller shaft (4) or to an extension of a gearbox shaft that is coaxial with the propeller shaft (4).

17. The propulsion system according claim 16, wherein the propulsion system comprises a drive element (21 ) that is attached to a stationary structure of the ship in a non-rotating manner and arranged in a mechanical torque transmission connection with a pitch angle actuation pump (12), electric generator (16) and / or another device (14) of the power unit (10) so that rotating movement of the propeller shaft (4) or the gearbox shaft of the ship drives said pump (12), said electric generator (16) and / or said other device (14).

18. The propulsion system according to claim 17, wherein the drive element (21 ) is a gearwheel.

19. The propulsion system according to claim 17 to 18, wherein the drive element (21 ) is arranged around the propeller shaft (4).

20. The propulsion system according to any of claims 17 to 19, wherein the propulsion system is provided with at least one support rod (22) having a first end attached to the drive element (21 ) and a second end that is attached to a stationary structure of the ship to prevent rotation of the drive element (21 ).21 . The propulsion system according to any of claims 17 to 20, wherein the propulsion system comprises hydraulically operable pitch angle actuation means (31 , 32).

22. The propulsion system according to claim 21 , wherein the power unit (10) comprises a hydraulic fluid inlet that is configured to allow supply of pressurized hydraulic fluid into the power unit (10) and further to the pitch angle actuation means (31 , 32) when the power unit (10) is stationary toallow emergency operation of the pitch angle actuation means (31 , 32), and the propulsion system comprises a hydraulic unit for supplying pressurized hydraulic fluid into the power unit (10) via the hydraulic fluid inlet.

23. The propulsion system according to claim 22, wherein the hydraulic unit comprises a hydraulic pump and / or a pressure accumulator.

24. The propulsion system according to any of claims 16 to 23, wherein the propulsion system comprises a pitch angle sensor (27).

25. The propulsion system according to claim 24, wherein the pitch angle sensor (27) is connected to wireless communication means (28) that are configured to communicate with a pitch angle control unit (29).

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