Propulsion units for ships

Abstract

The present disclosure relates to a propulsion unit (1) for a ship, comprising: a hull structure (2); a shaft (4) rotatably coupled to a propulsion motor (3) inside the hull structure (2); and a thruster (5) coupled to the shaft (4) outside the hull structure (2). A shaft sealing device (6) is arranged to engage the shaft (4) so ​​that at least one first sealing chamber (6a) is defined between adjacent sealing lips (6') and the shaft (4). A first lubrication device is provided for circulating a first lubricant through the first sealing chamber (6a). The first lubrication device (7) further comprises a first lubricant heat exchanger (7e), which is arranged at least partially outside the hull structure (2) for guiding the first lubricant therethrough and for transferring heat from the first lubricant to an environment outside the hull structure (2).

Description

Technical Field

[0001] The present invention relates to a propulsion unit for a ship, and more particularly to a shaft sealing device for such a propulsion unit. Background Art

[0002] The drive shaft of a ship propulsion unit needs to be sealed so that the surrounding water does not enter the structure surrounding the drive shaft via the interface between them. Typically, the shaft seal is provided with at least one sealing lip pressed against the drive shaft to ensure adequate sealing. Conventionally, such a sealing lip is shaped so that the static pressure of the ambient fluid exerts a radial force on the sealing lip so that it is firmly pressed against the drive shaft. In order to prevent this radial force from becoming too large, thereby causing excessive wear, a plurality of sealing lips have been provided so that corresponding sealing chambers are formed between axially adjacent sealing lips. Such a sealing chamber allows the pressure to gradually change from the static pressure of the fluid outside the structure from which the drive shaft protrudes to the pressure inside the structure. Therefore, each sealing lip only needs to seal against a portion of the total pressure difference, resulting in smaller radial forces and increased seal life.

[0003] In addition, if a plurality of such sealed chambers are provided, conventional devices may include the lubricant introduced into the inner sealed chamber. In this case, air pressure is usually introduced into the middle or outer sealed chamber to prevent lubricant contamination.

[0004] Normally, it has been considered that the water surrounding the structure from which the propeller protrudes provides sufficient cooling for any friction heat caused by the sealing lip pressed against the rotating drive shaft. It has now been surprisingly found that the sealing lip can still reach temperature levels that exceed the temperature level allowed based on its material properties, thereby causing premature wear. Summary of the invention

[0005] It is an object of the present invention to provide a propulsion unit equipped with a shaft sealing arrangement which provides more effective cooling of its sealing lips.

[0006] The objects of the invention are achieved by a propulsion unit which is characterized by what is stated in the independent claim. Preferred embodiments of the disclosure are disclosed in the dependent claims.

[0007] The invention is based on the idea of ​​providing a lubricant flow through a sealing chamber formed between axially adjacent sealing lips. More specifically, this lubricant flow is conducted through a heat exchanger which is at least partially exposed to the environment surrounding the housing structure of the propulsion unit. Thus, the lubricant serves to carry away excess heat from the sealing chamber and transfer it to the surrounding environment.

[0008] An advantage of the method and apparatus of the present disclosure is that a simple solution for effective cooling is achieved.

[0009] According to a first aspect of the invention, there is provided a propulsion unit for a vessel, such as a heading propulsion unit. The propulsion unit comprises a hull structure mountable beneath the hull of an associated vessel such that the hull structure is at least partially submerged in water when in use. Most suitably, the propulsion unit is fully submerged in water when in use.

[0010] The propulsion unit further comprises a shaft and a propeller, wherein the shaft extends between the inside and the outside of the housing structure through an opening provided at the housing structure, and the propeller is coupled to the shaft outside the housing structure so as to be rotatable by the shaft.

[0011] The propulsion unit further comprises a shaft sealing arrangement for sealing the interior of the housing structure from the surrounding external environment at the interface of the housing structure and the transmission shaft. The shaft sealing arrangement in turn comprises a plurality of sealing lips axially spaced from each other and engaging the outer periphery of the shaft such that at least one first sealing chamber is defined between adjacent sealing lips and the outer periphery of the shaft. In the context of the present disclosure, the shaft may comprise an assembly comprising an element other than the shaft which rotates with the shaft. For example a shaft sleeve.

[0012] The propulsion unit further comprises a first lubrication device, which in turn comprises a first lubricant circulator. The first lubrication device further comprises a first lubricant feed line for guiding the first lubricant to the first sealed chamber via the first lubricant circulator and a first lubricant return line for guiding the first lubricant from the first sealed chamber back to the first lubricant circulator. It should be noted that the first feed line and the first return line may guide the first lubricant via additional entities not mentioned above.

[0013] Preferably, but not necessarily, the first lubricating device further comprises a first lubricant reservoir for holding the first lubricant. For example, the first lubricant reservoir may be implemented as the first lubricant feed line, the first lubricant return line and / or any additional flow lines associated with the first lubricating device. Most preferably, the first lubricant reservoir is implemented as a dedicated first lubricant tank. In this case, the first lubricant circulator is suitably arranged for supplying the first lubricant from the first lubricant tank to the first sealed chamber via the first lubricant feed line. Accordingly, the first lubricant feed line is then suitably arranged to guide the first lubricant from the first sealed chamber back to the first lubricant tank. However, it should be noted that other arrangements are also possible. For example, the first lubricant circulator may alternatively be arranged to be connected to the first lubricant return line. Preferably, but not necessarily, the first lubricant circulator is arranged as a pump.

[0014] Furthermore, the first lubricating device further comprises a first lubricant heat exchanger, which is arranged at least partially in contact with the external environment of the housing structure 2, for guiding the first lubricant through the first heat exchanger 7e and for transferring heat from the first lubricant to the external environment of the housing structure. That is, when in use, the first heat exchanger is at least partially in direct contact with the water in which the propulsion unit is at least partially immersed, so that excess heat taken away from the shaft sealing device by the lubricant can be transferred in the surrounding water. For example, the first heat exchanger can be arranged at least on one side outside the housing structure. For example, the first heat exchanger can be implemented as a separate dedicated component, or by arranging a part of the pipeline associated with the first lubricating device to be at least partially exposed to the environment of the housing structure surrounding the propulsion unit.

[0015] It should be noted that in the context of the present disclosure, unless explicitly stated otherwise, terms such as first, second, third or fourth are not used to imply the number or order of the referred entities but are used to distinguish them from one another.

[0016] Preferably, but not necessarily, the propulsion unit may further comprise a propulsion motor 3 arranged within the hull structure. The propulsion motor is rotatably coupled to the shaft so that the propeller can be rotated by the propulsion motor. Most suitably, the propulsion motor is an electric motor equipped with electricity generated by the main motion of the associated vessel.

[0017] In an embodiment according to the first aspect of the present disclosure, the shaft sealing device may comprise a plurality of sealing lips, such that additionally at least one second sealing chamber is defined between adjacent sealing lips and the outer periphery of the shaft. Most suitably, the second sealing chamber is arranged axially adjacent to the first sealing chamber.

[0018] The shaft sealing device may further comprise a second lubricating device, which in turn comprises a second lubricant circulator. The second lubricating device further comprises a second lubricant feed line for guiding the second lubricant to the second sealed chamber via the second lubricant circulator and a second lubricant return line for guiding the second lubricant from the second sealed chamber back to the second lubricant circulator. It should be noted that the first feed line and the first return line may guide the first lubricant via additional entities not mentioned above.

[0019] Preferably, but not necessarily, the second lubricating device further comprises a second lubricant reservoir for holding the second lubricant. For example, the second lubricant reservoir may be implemented as the second lubricant feed line, the second lubricant return line and / or any additional flow line associated with the second lubricating device. Most suitably, the second lubricant reservoir is implemented as a dedicated second lubricant tank. In this case, the second lubricant circulator is suitably arranged to supply the second lubricant from the second lubricant tank to the second sealed chamber via the second lubricant feed line. Accordingly, the second lubricant feed line is then suitably arranged to guide the second lubricant from the second sealed chamber back to the second lubricant tank. However, it should be noted that other arrangements are also possible. For example, the second lubricant circulator may alternatively be arranged to be connected to the second lubricant return line.

[0020] Preferably, but not necessarily, the first lubricant circulator is configured as a pump.

[0021] Furthermore, the second lubricant device comprises a second lubricant heat exchanger, which is arranged at least partially in contact with the environment outside the housing structure, for guiding the second lubricant through the second heat exchanger and for transferring heat from the second lubricant to the environment outside the housing structure. That is, in use, the second heat exchanger is at least partially in direct contact with the water in which the propulsion unit is at least partially immersed, so that excess heat carried away from the shaft sealing device by the lubricant can be transferred to the surrounding water. For example, the second heat exchanger can be arranged at least on one side outside the housing structure. For example, the second heat exchanger can be implemented as a separate dedicated component or by arranging a part of the pipeline associated with the second lubricating device to be at least partially exposed to the environment of the housing structure surrounding the propulsion unit.

[0022] In an embodiment according to the first aspect of the present disclosure, the shaft sealing device comprises a plurality of sealing lips, so that additionally at least one third sealing chamber is defined between adjacent sealing lips and the outer periphery of the shaft. In this case, the third sealing chamber is suitably arranged axially adjacent to the second sealing chamber.

[0023] The propulsion unit may also include a pressurized medium supply line in fluid communication with the third sealed chamber, so that the fluid pressure in the third sealed chamber can be adjusted by setting the desired pressure of the air supply line. In particular, this makes it possible to adjust the fluid pressure in the third sealed chamber, thereby offsetting the static pressure of the fluid outside the shell structure of the propulsion unit. Most appropriately, pressurized air is used as a medium for regulating the pressure in the third sealed chamber. Advantageously, such a pressurized medium supply line is also fluidly connected to the second lubricant reservoir so as to adjust the pressure therein, most appropriately corresponding to the pressure in the third sealed chamber. The first lubricant reservoir may also be fluidly connected to the pressurized medium supply line, appropriately via a regulator for controlling the pressure in the first lubricant reservoir, advantageously lower than the pressure in the first lubricant reservoir. The pressure in one or more of the pressurized medium supply line, the second lubricant reservoir and the third sealed chamber may also be controlled with one or more common or public regulators.

[0024] For example, a flow regulator or a pressure regulator can be used as such a regulator.

[0025] Such a regulator may be supplied, for example, by a pressurized medium supply, such as a compressed air supply. Furthermore, such a regulator may be in fluid communication with either or both of the first lubricant reservoir or the second lubricant reservoir for supplying pressurized medium. That is, the reservoir pressures within the first lubricant reservoir and the second lubricant reservoir may be set by a pressurized medium supply, respectively, and then supply the regulator for regulating the pressure in the third sealed chamber.

[0026] Furthermore, such a third sealed chamber may be coupled to a drain reservoir via a drain line in order to drain from the third sealed chamber any fluid (eg water or lubricant) leaking from any axially adjacent sealed chamber.

[0027] In an embodiment according to the first aspect of the present disclosure, the shaft sealing device comprises a plurality of sealing lips, so that additionally at least one fourth sealing chamber is defined between adjacent sealing lips and the outer periphery of the shaft. Most suitably, the fourth sealing chamber is arranged axially adjacent to the third sealing chamber. Furthermore, the fourth sealing chamber is preferably the axially outermost sealing chamber, so that the axially outermost sealing lip associated with the fourth sealing chamber is in direct contact with the surrounding water when in use.

[0028] It should be noted that the present invention also encompasses devices having other sealed chambers than those mentioned in connection with the above embodiments.

[0029] In an embodiment according to the first aspect of the invention, the first heat exchanger is preferably arranged upstream of the first sealed chamber. This prevents any pressure loss on the first heat exchanger from increasing the pressure in the first sealed chamber. Alternatively or additionally, the first heat exchanger can be provided downstream of the first sealed chamber.

[0030] In an embodiment according to the first aspect of the invention, where a second lubrication device is provided, the second heat exchanger is preferably arranged upstream of the second sealed chamber. This prevents any pressure loss on the second heat exchanger from increasing the pressure in the second sealed chamber. Alternatively or additionally, the second heat exchanger may be arranged downstream of the second sealed chamber.

[0031] In an embodiment according to the first aspect of the present disclosure, the first lubrication device may also be equipped with a first bypass valve for selectively directing the first lubricant flow to bypass the first heat exchanger. This allows the first lubricant to be directed to bypass the first heat exchanger, for example, in the event of a heat exchanger failure.

[0032] In an embodiment according to the first aspect of the invention, where a second lubrication device is provided, the second lubrication device may also be equipped with a second bypass valve for selectively directing the second lubricant flow through the second heat exchanger. This allows the first lubricant to be directed to bypass the first heat exchanger, for example in the event of damage to the heat exchanger.

[0033] In an embodiment according to the first aspect of the invention, the portion of the first heat exchanger outside the housing structure is arranged on the outer end surface of the housing structure facing the propeller. This arrangement provides protection for the first heat exchanger, as the propeller protects the heat exchanger from potential collisions with external objects, such as ice. Preferably, but not necessarily, the first heat exchanger may at least partially surround the transmission shaft in an annular manner. Preferably, but not necessarily, the portion of the first heat exchanger may be at least partially covered by a separate fairing, such as a rope sheath, which further provides additional protection for the heat exchanger.

[0034] In an embodiment according to the first aspect of the invention, in the case where a second lubrication device is provided, a portion of the second heat exchanger outside the housing structure is arranged on an outer end surface of the housing structure facing the propeller. This arrangement provides protection for the second heat exchanger, since the propeller protects the heat exchanger from potential collisions with external objects, such as ice. Preferably, but not necessarily, the second heat exchanger may at least partially surround the transmission shaft in an annular manner. Preferably, but not necessarily, the portion of the second heat exchanger may be at least partially covered by a separate fairing, such as a rope sheath, which further provides additional protection for the heat exchanger.

[0035] In an embodiment according to the first aspect of the invention, the first lubrication device may include a first sensor configured to generate a first sensor signal indicative of a first lubricant property. The first sensor may then be coupled to a control unit configured to adjust an output flow of the first lubricant circulator based on the first sensor signal.

[0036] Preferably, but not necessarily, the control unit is configured to adjust the output flow of the first lubricant circulator by controlling an associated circulator motor, the associated circulator motor being configured to drive the first lubricant circulator. Alternatively or additionally, a variable displacement circulator may be used and arranged to be controlled by the control unit.

[0037] For example, the first sensor may be arranged as a first temperature sensor, which is configured to generate a first sensor signal indicating a first lubricant temperature. Most suitably, the first temperature sensor is configured to generate a first sensor signal indicating a first lubricant temperature. Advantageously, the first temperature sensor is arranged downstream of the first sealing chamber, but may also be arranged upstream of the first sealing chamber. Furthermore, the control unit may advantageously be configured to increase the output flow of the first lubricant circulator if the first sensor signal indicates an excessively high first lubricant temperature. Alternatively or additionally, the control unit is advantageously configured to reduce the output flow of the first lubricant circulator if the first sensor signal indicates an insufficient first lubricant temperature. This arrangement provides sufficient lubricant flow to ensure proper lubrication and cooling when the temperature of the lubricant increases and its viscosity decreases. Accordingly, when the temperature of the lubricant decreases and its viscosity increases, excessive lubricant flow, which leads to increased sealing chamber pressure and premature wear of the sealing lip, is prevented.

[0038] Such excess or insufficient lubricant temperature may be appropriately determined based on the lubricant used and the specification and material of the sealing device. Advantageously, the output flow of the first lubricant circulator is controlled by the control unit based on the lubricant temperature according to a predetermined control curve, chart or map.

[0039] As another example, the first sensor may be arranged as a first pressure sensor indicating a first lubricant pressure in the first sealing chamber. Furthermore, the control unit is advantageously configured to increase the output flow of the first lubricant circulator if the first sensor signal indicates an insufficient first lubricant pressure. Alternatively or additionally, the control unit is advantageously configured to reduce the output flow of the first lubricant circulator if the first sensor signal indicates an excessive first lubricant pressure. In a similar manner, this arrangement also prevents excessive lubricant pressure in the sealing chamber from causing excessive wear of the sealing lip while ensuring sufficient lubrication.

[0040] Furthermore, such excess or insufficient lubricant pressure can be appropriately determined based on the lubricant used and the specifications and materials of the sealing device. Advantageously, the output flow of the first lubricant circulator is controlled by the control unit based on the lubricant temperature according to a corresponding predetermined control curve, chart or map.

[0041] It is also possible to use both the first pressure sensor and the first temperature sensor simultaneously to control the first lubricant circulator.

[0042] In an embodiment according to the first aspect of the present invention, in the case where a second lubrication device is provided, the second lubrication device may include a second sensor configured to generate a second sensor signal indicative of a second lubricant property. The second sensor may then be coupled to the control unit, which is configured to adjust the output flow of the second lubricant circulator based on the second sensor signal.

[0043] Preferably, but not necessarily, the control unit is configured to adjust the output flow of the second lubricant circulator by controlling an associated circulator motor, the associated circulator motor being configured to drive the second lubricant circulator. Alternatively or additionally, a variable displacement circulator may be used and arranged to be controlled by the control unit.

[0044] For example, the second sensor may be arranged as a second temperature sensor, which is configured to generate a second sensor signal indicating the second lubricant temperature. Advantageously, the second temperature sensor is arranged downstream of the second sealing chamber, but may also be arranged upstream of the second sealing chamber. Furthermore, the control unit may advantageously be configured to increase the output flow of the second lubricant circulator if the second sensor signal indicates a second lubricant temperature that is too high. Alternatively or additionally, the control unit is advantageously configured to reduce the output flow of the second lubricant circulator if the second sensor signal indicates an insufficient second lubricant temperature. This arrangement provides sufficient lubricant flow to ensure proper lubrication and cooling when the temperature of the lubricant increases and its viscosity decreases. Accordingly, when the temperature of the lubricant decreases and its viscosity increases, an excessive lubricant flow that leads to an increase in the sealing chamber pressure and premature wear of the sealing lip is prevented.

[0045] Such excess or insufficient lubricant temperature may be appropriately determined based on the lubricant used and the specification and material of the sealing device. Advantageously, the output flow of the second lubricant circulator is controlled by the control unit based on the lubricant temperature according to a corresponding predetermined control curve, chart or map.

[0046] As another example, the second sensor may be arranged as a second pressure sensor indicating a second lubricant pressure in the second sealing chamber. Furthermore, the control unit is advantageously configured to increase the output flow of the second lubricant circulator if the second sensor signal indicates an insufficient second lubricant pressure. Alternatively or additionally, the control unit is advantageously configured to reduce the output flow of the second lubricant circulator if the second sensor signal indicates an excessive second lubricant pressure. In a similar manner, this arrangement also prevents excessive lubricant pressure in the sealing chamber from causing excessive wear of the sealing lip while ensuring sufficient lubrication.

[0047] Furthermore, such excess or insufficient lubricant pressure can be appropriately determined based on the lubricant used and the specifications and materials of the sealing device. Advantageously, the output flow of the first lubricant circulator is controlled by the control unit based on the lubricant temperature according to a corresponding predetermined control curve, chart or map.

[0048] It is also possible to use both the first pressure sensor and the first temperature sensor simultaneously to control the first lubricant circulator.

[0049] In an embodiment according to the first aspect of the present disclosure, wherein a second lubrication device is provided, both the first lubricant circulator and the second lubricant circulator are driven by a common circulator motor.

[0050] It should be noted that the first aspect of the present disclosure covers any combination of two or more embodiments as discussed above or variations thereof.

[0051] According to a second aspect of the present invention, a vessel is provided. In particular, the vessel comprises one or more propulsion units according to the first aspect of the present invention as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Hereinafter, the present disclosure will be described in more detail by way of preferred embodiments with reference to the accompanying drawings, in which

[0053] Figure 1 is a schematic diagram of a propulsion unit according to an embodiment of the present invention;

[0054] Figure 2 yes Figure 1 A more detailed schematic diagram of .

[0055] Figure 3 is a partial cross-sectional view of a propulsion unit according to an embodiment of the present disclosure as seen from a perspective view;

[0056] Figure 4 yes Figure 3 A perspective view of the propulsion unit is shown, and

[0057] Figure 5yes Figure 3 A perspective view of a propulsion unit is shown with the heat exchanger covered. DETAILED DESCRIPTION

[0058] Figure 1 is a schematic diagram of a propulsion unit according to an embodiment of the present invention. In particular, the propulsion unit 1 is intended to be coupled to a vessel under its hull. The propulsion unit 1 has a housing structure, i.e. a housing, in which a propulsion motor 3 is accommodated. A propeller 5 is arranged outside the housing structure 2 and is coupled to the propulsion motor 3 via a transmission shaft 4. The transmission shaft 4 passes through the housing structure 2, while a shaft sealing device 6 seals the interior of the housing structure 2 from the outside of the housing structure 2 at the interface of the transmission shaft 4 and the housing structure 2. A first lubricating device 7 and a second lubricating device 8 are provided for lubricating and cooling the shaft sealing device 6, and a control unit 10 is provided for controlling the lubricating devices 7, 8.

[0059] Figure 2 yes Figure 1 A more detailed schematic diagram of the first lubrication device, the second lubrication device and other entities associated therewith of the illustrated embodiment. Specifically, the shaft sealing device 6 comprises a plurality of sealing lips 6' engaged with the transmission shaft 4. A first sealing chamber 6a is defined between the axially adjacent sealing lips 6' and the transmission shaft 4. Figure 2 In the embodiment shown, the first sealing chamber is also the axially innermost sealing chamber. The second sealing chamber 6b is also defined between the axially adjacent sealing lip 6' and the transmission shaft 4. In the illustrated embodiment, the second sealing chamber 6b is axially adjacent to the first sealing chamber 6a, that is, they are separated by mutual sealing lips. The third sealing chamber 6c is also defined between the axially adjacent sealing lip 6' and the transmission shaft 4. In the illustrated embodiment, the third sealing chamber 6c is axially adjacent to the second sealing chamber 6b, that is, they are separated by mutual sealing lips 6'. The fourth sealing chamber 6d is also defined between the axially adjacent sealing lip 6' and the transmission shaft 4. In the illustrated embodiment, the fourth sealing chamber 6c is the axially outermost sealing chamber and is axially adjacent to the third sealing chamber 6c, that is, they are separated by mutual sealing lips 6'.

[0060] The first sealed chamber 6a is associated with the first lubricating device 7 so that the first lubricant lubricates and cools the first sealed chamber and the sealing lip 6' associated therewith. In particular, the first lubricant from the first lubricant reservoir 7a provided as a separate tank is circulated through the first sealed chamber 6a by the first lubricant circulator 7b, after which the first lubricant is returned to the first lubricant reservoir 7a again. Before entering the first sealed chamber 6a, the first lubricant is guided through a first heat exchanger 7e, which is at least partially in contact with the environment around the housing structure, so that a heat exchange between the first lubricant and the surrounding environment is achieved. A first bypass valve 7f is also arranged in connection with the first heat exchanger so that, for example, in the event of failure of the first heat exchanger 7e, the first lubricant can be guided through the first heat exchanger 7e, thereby preventing the risk of lubricant leaking to the surrounding environment. In the embodiment shown, the first bypass valve 7f also provides a closed position, in which the circulation of the first lubricant is completely stopped. The first lubricating device is also provided with a first sensor 7g. In the embodiment shown, the first sensor 7g is a temperature sensor arranged downstream of the first sealed chamber 6a, but other types of sensors and their arrangements can also be envisaged. The first sensor 7g is coupled to a control unit 10 which regulates the output flow of the first lubricant circulator 7b by controlling a circulator motor 7b' driving the first lubricant circulator.

[0061] In a similar manner, the second sealed chamber 6b is associated with the second lubricating device 8, so that the second lubricant lubricates and cools the second sealed chamber and the sealing lip 6' associated therewith. In particular, the second lubricant from the second lubricant reservoir 8a provided as a separate tank is circulated through the second sealed chamber 6b by the second lubricant circulator 8b, and the second lubricant is returned to the second lubricant reservoir 8a again. Before entering the second sealed chamber 6b, the second lubricant is guided through the second heat exchanger 8e, which is at least partially in contact with the environment around the housing structure, thereby achieving heat exchange between the second lubricant and the surrounding environment. The second bypass valve 8f is also arranged to be coupled to the second heat exchanger, so that, for example, in the event of failure of the second heat exchanger 8e, the second lubricant can be guided through the second heat exchanger 8e, thereby preventing the risk of lubricant leakage to the surrounding environment. In the illustrated embodiment, the second bypass valve 8f also provides a closed position, in which the second lubricant circulation is completely stopped. The second lubricating device 8 is also provided with a second sensor 8g. In the embodiment shown, the second sensor 8g is a temperature sensor arranged downstream of the second sealed chamber 6b, but other types of sensors and their arrangements are also conceivable. The second sensor 8g is coupled to a control unit 10, which regulates the output flow of the second lubricant circulator 8b by controlling a circulator motor 8b' driving the second lubricant circulator.

[0062] In the illustrated embodiment, the first lubricant reservoir 7a is coupled to a first lubricant supply line 7a' for filling the first lubricant reservoir 7a. Correspondingly, the second lubricant reservoir 8a is coupled to a second lubricant supply line 8a' for filling the second lubricant reservoir 8a.

[0063] In the illustrated embodiment, both the first lubricant circulator 7a and the second lubricant circulator 8a are driven by the same circulator motor 7b', 8b', although separate motors may also be implemented.

[0064] In the illustrated embodiment, the air supply line 11 is coupled to the second lubricant reservoir 8a and also to the first lubricant reservoir 7a via a corresponding regulator in order to set a desired reservoir pressure in the first lubricant reservoir 7a lower than the pressure of the air supply line 11 .

[0065] In addition, the air supply line 11 is also coupled to the third sealed chamber 6c along the regulator line 9a, so that the pressure in the third sealed chamber 6c can be adjusted. That is, the pressure in the third sealed chamber is set so as to offset the hydrostatic pressure in the environment around the housing structure 2, that is, to smooth the pressure difference acting on the sealing device 6. Although other arrangements are possible, the drawings show an embodiment in which the pressure in the second lubricant reservoir 8a and the third sealed chamber 6c is controlled by the pressure in the air supply line 11, while a separate regulator for controlling the pressure in the first lubricant reservoir 7a is provided.

[0066] The third sealed chamber 6c is also coupled to a drain reservoir 9c via a drain line 9b. This enables any water in the fourth sealed chamber 6d or lubricant leaking from the second sealed chamber 6b into the third sealed chamber 6c to be drained therefrom. Effectively, any lubricant from the second sealed chamber 6b is prevented from contaminating the environment surrounding the housing structure 2.

[0067] When in use, the first and second sealed chambers 6a, 6b are mainly occupied by the first and second lubricants respectively. The third sealed chamber 6c is mainly occupied by air supplied via the regulator line 9a, while the fourth sealed chamber 6d is mainly occupied by water from the surrounding environment.

[0068] Figure 3 is a partial cross-sectional view of a propulsion unit 1 according to an embodiment of the present disclosure as seen from a perspective view. In particular, Figure 3 A housing structure 2 is shown which defines an interior space and, as mentioned above, accommodates components of the propulsion unit 1. Furthermore, a portion of the shaft 4 can be seen, namely its sleeve extending through the housing structure 2. A sealing device 6 is provided around the transmission shaft 4. Furthermore, portions of a first heat exchanger 7e and a second heat exchanger 8e can be seen on the end face of the housing structure 2 around the transmission shaft 4.

[0069] Figure 4 yes Figure 3 A perspective view of a propulsion unit is shown. Figure 4 The arrangement of the first heat exchanger and the second heat exchanger annularly around the drive shaft 4 is shown more clearly.

[0070] Figure 5 yes Figure 3 and Figure 4 A perspective view of a propulsion unit is shown. Except for the heat exchanger which is covered by a separate fairing in the form of a ropeguard 12.

[0071] Although the figures discuss the invention in conjunction with an embodiment employing a first lubricating device 7 and a second lubricating device, it should be understood that the invention encompasses a propulsion unit implemented with a single lubricating device, or alternatively, a propulsion unit implemented with more than two lubricating devices.

[0072] Reference numerals list

[0073] 1 Propulsion unit

[0074] 2 Shell structure

[0075] 3 Propulsion motor

[0076] 4 Axis

[0077] 5. Thrusters

[0078] 6 Shaft sealing device

[0079] 6' Sealing Lip

[0080] 6a First sealed chamber

[0081] 6b Second sealed chamber

[0082] 6c Third sealed chamber

[0083] 6d Fourth Sealed Chamber

[0084] 7. First lubrication device

[0085] 7a First lubricant reservoir

[0086] 7a' First lubricant supply line

[0087] 7b First lubricant circulator

[0088] 7b' First lubricant circulator motor

[0089] 7c Fir lubricant feed line

[0090] 7d First lubricant return line

[0091] 7e First lubricant heat exchanger

[0092] 7f First bypass valve

[0093] 7g First Sensor

[0094] 8 Second lubrication device

[0095] 8a Second lubricant reservoir

[0096] 8a' Second lubricant supply line

[0097] 8b Second lubricant circulator

[0098] 8b' Second lubricant circulator motor

[0099] 8c Second lubricant feed line

[0100] 8d Second lubricant return line

[0101] 8e Second lubricant heat exchanger

[0102] 8f Second bypass valve

[0103] 8g Second sensor

[0104] 9a Regulator line

[0105] 9b Discharge line

[0106] 9c Discharge reservoir

[0107] 10 Control unit

[0108] 11 Air supply line

[0109] 12 Rope sheath

Claims

1. A propulsion unit (1) for a ship, the propulsion unit comprising: a hull structure (2) which is mountable beneath the hull of an associated vessel such that the hull structure (2) is at least partially submerged in water when in use; a shaft (4) extending between the interior and the exterior of the housing structure (2) through an opening provided at the housing structure; a propeller (5) coupled to the shaft (4) outside the housing structure (2) so as to be rotatable by the shaft (4); A shaft sealing device (6) comprising a plurality of sealing lips (6') axially spaced from each other and engaging the outer periphery of the shaft (4) such that at least a first sealing chamber (6a) is defined between adjacent sealing lips (6') and the outer periphery of the shaft (4), and A first lubricating device (7), the first lubricating device comprising in sequence: - a first lubricant circulator (7b); a first lubricant feed line (7c) for conducting a first lubricant to the first sealed chamber (6a) via the first lubricant circulator (7b), and - a first lubricant return line (7d) for guiding the first lubricant from the first sealed chamber (6a) back to the first lubricant circulator (7b), wherein the first lubricating device (7) further comprises a first lubricant heat exchanger (7e), the first lubricant heat exchanger being arranged to be at least partially in contact with an external environment of the housing structure (2), for guiding the first lubricant through the first lubricant heat exchanger (7e) and for transferring heat from the first lubricant to the external environment of the housing structure (2); wherein the shaft sealing device (6) further comprises a plurality of sealing lips (6'), such that additionally at least a second sealing chamber (6b) is defined between adjacent sealing lips (6') and the outer periphery of the shaft (4), The invention is characterized in that it further comprises a second lubricating device (8), wherein the second lubricating device comprises in sequence: - a second lubricant circulator (8b); - a second lubricant feed line (8c) for guiding a second lubricant to the second sealed chamber (6b) via the second lubricant circulator (8b); - a second lubricant return line (8d) for guiding the second lubricant from the second sealed chamber (6b) back to the second lubricant circulator (8b), and a second lubricant heat exchanger (8e) arranged at least partially outside the housing structure for conducting a second lubricant through the second lubricant heat exchanger and for transferring heat from the second lubricant to an environment outside the housing structure, wherein the shaft sealing device (6) comprises a plurality of sealing lips (6') such that additionally at least a third sealing chamber (6c) is defined between adjacent sealing lips (6') and the outer periphery of the shaft (4), The propulsion unit (1) further comprises a regulator in fluid communication with the third sealed chamber (6c), so that the fluid pressure in the third sealed chamber (6c) can be adjusted by the regulator. wherein the shaft sealing device (6) comprises a plurality of sealing lips (6') such that additionally at least one fourth sealing chamber (6d) is defined between adjacent sealing lips (6') and the outer periphery of the shaft (4), wherein the fourth sealing chamber (6d) is the axially outermost sealing chamber, so that the axially outermost sealing lip (6') associated with the fourth sealing chamber (6d) is in direct contact with the surrounding water during use, and The third sealed chamber (6c) is also coupled to a drain reservoir (9c) via a drain line (9b) so that water from the fourth sealed chamber (6d) or the second lubricant leaking from the second sealed chamber (6b) into the third sealed chamber (6c) can be discharged therefrom.

2. The propulsion unit (1) according to claim 1, characterized in that The portion of the first lubricant heat exchanger (7e) located outside the housing structure (2) is arranged on the outer end surface of the housing structure (2) facing the propeller (5).

3. The propulsion unit (1) according to claim 2, characterized in that The portion of the first lubricant heat exchanger (7e) is at least partially covered by a fairing.

4. The propulsion unit (1) according to claim 3, characterized in that The fairing is a rope sheath (12).

5. The propulsion unit (1) according to any one of the preceding claims 1 to 3, characterized in that The portion of the second lubricant heat exchanger (8e) located outside the housing structure (2) is arranged on the outer end surface of the housing structure (2) facing the propeller.

6. The propulsion unit (1) according to claim 5, characterized in that The portion of the second lubricant heat exchanger (8e) is at least partially covered by a fairing.

7. The propulsion unit (1) according to claim 6, characterized in that The fairing is a rope sheath (12).

8. A propulsion unit (1) according to any one of the preceding claims 1 to 4, characterised in that The first lubrication device (7) comprises a first sensor (7g), the first sensor (7g) being configured to generate a first sensor signal indicating a first lubricant property, the first sensor (7g) being coupled to a control unit (10), the control unit (10) being configured to adjust an output flow of the first lubricant circulator (7b) based on the first sensor signal.

9. The propulsion unit according to claim 8, characterized in that The control unit (10) is configured to adjust the output flow of the first lubricant circulator (7b) by controlling an associated circulator motor (7b'), the circulator motor (7b') being configured to drive the first lubricant circulator (7b).

10. The propulsion unit according to claim 8, characterized in that The first sensor (7g) is arranged as a first temperature sensor, the first temperature sensor being configured to generate a first sensor signal indicating a first lubricant temperature, and wherein the control unit (10) is configured to - if the first sensor signal indicates a first lubricant temperature that is too high, increase the output flow of the first lubricant circulator (7b), and / or - if the first sensor signal indicates an insufficient first lubricant temperature, reducing the output flow of the first lubricant circulator (7b), Alternatively, the first sensor (7g) is configured as a first pressure sensor for indicating a first lubricant pressure in the first sealed chamber (6a), and wherein the control unit (10) is configured to - if the first sensor signal indicates insufficient first lubricant pressure, increasing the output flow of the first lubricant circulator (7b), and / or - if the first sensor signal indicates a first lubricant pressure that is too high, reducing the output flow of the first lubricant circulator (7b).

11. The propulsion unit (1) according to any one of the preceding claims 1 to 4, characterized in that The second lubrication device (8) comprises a second sensor (8g) configured to generate a second sensor signal indicative of a second lubricant property, the second sensor being coupled to a control unit (10) configured to adjust an output flow of the second lubricant circulator (8b) based on the second sensor signal.

12. The propulsion unit (1) according to claim 11, characterized in that The control unit (10) is configured to adjust the output flow of the second lubricant circulator (8b) by controlling an associated circulator motor (8b'), the circulator motor (8b') being configured to drive the second lubricant circulator (8b).

13. The propulsion unit (1) according to claim 11, characterized in that The second sensor is arranged as a second temperature sensor, the second temperature sensor being configured to generate a second sensor signal indicative of a second lubricant temperature, and wherein the control unit is configured to - increase the output flow of the second lubricant circulator if the second sensor signal indicates a second lubricant temperature that is too high, and / or - if the second sensor signal indicates an insufficient second lubricant temperature, reducing the output flow of the second lubricant circulator, and / or The second sensor is arranged as a second pressure sensor, the second pressure sensor indicating a second lubricant pressure in the second sealed chamber, and wherein the control unit is configured to - increase the output flow of the second lubricant circulator if the second sensor signal indicates an insufficient second lubricant pressure, and / or If the second sensor signal indicates a second lubricant pressure that is too high, reducing the output flow of the second lubricant circulator.

14. The propulsion unit (1) according to any one of the preceding claims 1 to 4, characterized in that Both the first lubricant circulator (7b) and the second lubricant circulator (8b) are driven by a common circulator motor (7b', 8b').

15. A propulsion unit according to any one of the preceding claims 1 to 4, characterised in that It also includes a propulsion motor (3) arranged in the housing structure (2), and wherein the propulsion motor (3) is rotatably coupled to the shaft (4) so ​​that the propeller (5) can be rotated by the propulsion motor (3).

16. A propulsion unit according to any one of the preceding claims 1 to 4, characterised in that The propulsion unit is a heading propulsion unit.

17. A ship, characterized in that: Comprising a propulsion unit (1) according to any one of claims 1-16.

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