Underwater drive unit

Abstract

The present invention relates to an underwater drive unit (10), preferably for an outboard motor or pod-type propeller, comprising a plastic housing (1) designed to be surrounded by water and a metal housing (2) in which an electric drive (3) is housed, wherein the electric drive (3) is enclosed in the metal housing (2) in an airtight seal against the environment and the metal housing (2) is disposed within the plastic housing (1).

Description

Technical field

[0001] The present invention relates to an underwater propulsion unit comprising a plastic housing designed to be exposed to water flow and a metal housing with an electric drive. The present invention further relates to a system of at least two such underwater propulsion units. The present invention also relates to a boat with such an underwater propulsion unit. State of the art

[0002] Underwater propulsion units are frequently equipped with an electric drive. The development of electric underwater propulsion units is subject to several competing requirements.

[0003] On the one hand, the drive unit needs to be housed in a highly thermally conductive material to prevent the electric drive or its power components from overheating. For this reason, drive units are often mounted in metallic housings. On the other hand, the underwater drive unit must have optimal flow characteristics to minimize friction losses when exposed to water. This often involves the use of special coatings or at least exceptionally high-quality surface finishes. Furthermore, the metal housings must be protected from environmental influences, particularly from the resulting corrosion. However, combining a metal housing with low water resistance and a protective coating incurs significant costs. This contradicts another important requirement: cost savings.The development of underwater propulsion units, particularly for lower performance classes, involves a conflict of objectives between cooling, flow optimization, and cost reduction. Furthermore, the design of the underwater propulsion unit plays a role in its marketability. The prior art addresses individual aspects of this conflict.

[0004] EP 2 762 402 A2 discloses a propulsion unit for a ship in which the cooling of the propulsion unit is achieved by cooling the engine both from the inside and from the outside.

[0005] US patent 2004014380 A1 discloses a ship propulsion system which has an electric motor in a housing and also has flow openings through which the propulsion unit can be cooled.

[0006] US patent 20070173140 A1 discloses an integrated outboard motor which has an electric drive in a plastic housing.

[0007] A disadvantage of the solutions known from the prior art, however, is that none of the known methods provides a satisfactory solution to the conflicting objectives of cooling, flow optimization, and cost savings. According to the prior art, either the housing is made of metal, which necessitates complex and expensive post-processing for flow optimization, or the housing is made of plastic, resulting in suboptimal cooling of the electric drive.

[0008] FR 2 823 177 A1 discloses a device with which water can be passed through the stator of an electric motor.

[0009] DE 10 2020 131 564 A1 discloses an electromechanical drive device for a floating device, wherein the drive comprises an electric motor which is housed in a casing, the casing having inlet openings through which the electric motor can be surrounded by water.

[0010] EP 3 809 565 A1 discloses a drive for a boat comprising a housing, wherein a cooling section is provided in the housing which is equipped with a cooling media channel. Description of the invention

[0011] Starting from the known state of the art, it is an object of the present invention to provide an improved underwater propulsion unit.

[0012] The problem is solved by an underwater unit with the features of claim 1. Advantageous further developments are described in the dependent claims, the description, and the figures.

[0013] Accordingly, an underwater drive unit, preferably for an outboard motor or a pod drive, is proposed, comprising a plastic housing designed for water flow and a metal housing in which an electric drive is accommodated. According to the invention, the electric drive is sealed watertight against the environment within the metal housing, and the metal housing is arranged inside the plastic housing.

[0014] Because the metal housing is waterproof and located inside the plastic housing, the functions of "cooling the electric drive" and "flow optimization" are separated. In other words, a "shell-within-a-shell" principle is used, namely a "metal housing-within-a-plastic housing" principle.

[0015] The function "cooling of the electric drive" is fulfilled by means of the metal housing, which has good thermal conductivity properties and thus efficiently transports heat from the electric drive to the medium surrounding the metal housing, water or plastic material.

[0016] The "flow optimization" function is achieved through the plastic housing, which can be easily and flexibly molded into any shape that is optimal for the specific application of the underwater drive unit. In particular, the use of a plastic housing eliminates the need for costly corrosion protection and flow-optimizing coatings compared to a metal housing, thus reducing manufacturing costs.

[0017] As a result, the metal housing does not require flow-optimized properties or special design features and can have a simple surface finish, making its construction particularly easy. This allows the metal housing to be supplied with a largely untreated surface. The metal housing can also be designed with a simple shape, such as a cylindrical form.

[0018] At the same time, the plastic housing does not need to have sealing properties. Therefore, the plastic housing can be designed solely with regard to flow requirements.

[0019] This underwater propulsion unit, comprising a water-permeable plastic housing and a metal housing containing an electric drive, optimally resolves the conflicting objectives of cost savings, flow optimization, and cooling. Furthermore, the crumple zone provided by the plastic housing protects the metal housing from damage caused by mechanical energy input, such as that which can occur during grounding, particularly water damage that could lead to total failure of the motor and electronics. Additionally, the plastic housing eliminates the need for further environmental protection of the metal housing.

[0020] An underwater unit within the meaning of the present disclosure is a pylon of an outboard motor or a pod which, in the nominal operation of the underwater propulsion unit, is located wholly or partially below the water surface.

[0021] For the purposes of this disclosure, a plastic housing can be understood to be a housing that comprises a plastic. In particular, it can be understood to be a housing made exclusively of one or more plastics or composite materials. The plastic housing can be coated or uncoated. In particular, the plastic housing can be painted. Alternatively or additionally, the plastic housing can have a surface embossing. Preferably, the surface embossing can be designed such that friction is reduced when water flows around the plastic housing.

[0022] For the purposes of this disclosure, a metal housing can be understood to mean a housing that incorporates metal. In particular, it can be understood to mean a housing made entirely of metal. For example, the housing may comprise a casting. Advantageously, the metal housing has an untreated surface. This allows for cost savings.

[0023] The term waterproof is to be understood as meaning that during the nominal operation of the underwater propulsion unit, no water or only a negligible amount of water can penetrate the metal housing.

[0024] Preferably, the electric drive of the underwater propulsion unit is designed for one of the lower power classes of underwater propulsion units, in particular as an electric drive with a power output of 0.2 hp to 80 hp, for example between 0.2 and 0.7 hp, 1 and 3 hp, 1.5 and 3 hp, 5 and 20 hp, or 40 and 80 hp (approx. 150 W to 500 W, 730 W to 2.2 kW, 1.1 and 2.2 kW, 3.6 and 14.7 kW, or 29.4 and 58 kW). This has the advantage that particularly high cost savings can be achieved in this power class with an underwater propulsion unit as disclosed herein.

[0025] According to the invention, the plastic housing has openings which are connected via a flow channel, wherein the plastic housing is designed such that, in the flow-around state of the plastic housing, at least a partial flow around the metal housing takes place.

[0026] Because the plastic housing has openings connected by a flow channel, and because the plastic housing is designed so that the flow around it at least partially surrounds the metal housing, the metal housing can be cooled particularly efficiently. A coating of the metal housing is not required, as it is not part of the outer structure and does not need to perform flow optimization. Therefore, the metal housing does not need to meet any special aerodynamic requirements. At the same time, the metal housing does not need to meet any aesthetic requirements, as it is not, or only minimally, visible from the outside.

[0027] Because the flow around the plastic housing is at least partially around the metal housing, cooling of the metal housing and thus of the drive components located inside it is possible during operation.

[0028] For the purposes of this disclosure, a plastic housing designed for water flow is understood to be a housing made of plastic and having a design, in particular an outer contour, that is optimized for water flow. Advantageously, the plastic housing comprises at least one inlet opening in the front region and at least one outlet opening in the rear region, the flow channel extending along the longitudinal axis L of the underwater drive unit. In other words, during operation of the underwater drive unit, water flowing around it can enter the plastic housing through the inlet opening, flow to the metal housing via the flow channel, and then exit the plastic housing through the outlet opening. This allows for continuous flow around the metal housing, thus ensuring optimal cooling of the drive component during operation.

[0029] Advantageously, the flow channel is at least partially formed by the metal housing. In other words, the metal housing forms at least a boundary or wall section of the flow channel. Because the flow channel is at least partially formed by the metal housing, water, when flowing around the plastic housing, comes into contact with the metal housing through the flow channel. This contact with the water optimizes heat transfer between the metal housing and the water, further improving cooling.

[0030] Advantageously, the plastic housing is connected to a shaft tube via a shaft tube molding. Because the plastic housing is connected to the shaft tube, the metal housing does not need to be welded or molded onto the shaft tube. Compared to established manufacturing methods such as welding the shaft tube to the metal housing or molding a shaft tube connection onto a metal housing as a casting, this significantly reduces production costs, as several manufacturing steps such as turning, drilling, welding, casting, and mechanical finishing are eliminated. Furthermore, connecting the shaft tube to the plastic housing allows for greater design freedom in both the plastic and metal housings.

[0031] The shaft tube can also be directly connected to the metal housing, for example by welding, riveting, or screwing it on, or by forming it as a single piece. Direct connection of the shaft tube to the metal housing can further improve structural strength. The plastic housing can also be connected to the shaft tube – for example, via the previously mentioned molded joint.

[0032] The plastic housing can also be held only by the metal housing, which in turn is connected to the shaft tube. In this configuration, the plastic housing can have a simple opening in the area where the shaft tube passes through, allowing the shaft tube to be inserted without any further fastening of the plastic housing.

[0033] Advantageously, the electric drive comprises an electric motor, optionally a gearbox and / or electronic components, and drives a propeller via a drive shaft. These components are then sealed watertight within the metal housing. The electric motor provides torque to drive the drive shaft. If necessary, the torque can be converted to a different torque / speed ratio via a gearbox.

[0034] Because the electric drive includes an electric motor, a gearbox, and / or an electronic component, all components necessary for driving the propeller via the drive shaft can be cooled by the metal housing, which is at least partially surrounded by water when the plastic housing is exposed to flow. The entire motor unit is thus housed in a metal casing, which, when the plastic housing is exposed to flow, is also at least partially surrounded by water and therefore cooled.

[0035] Advantageously, the metal housing is formed from a cylindrical metal tube, which includes a front tube seal at its front end and / or a rear tube seal at its rear end. This allows the metal housing to be made from a simple tube sealed at both ends with caps. In particular, the tube seal at the rear end can also be part of the metal housing, i.e., formed as a single piece with the metal housing.

[0036] Advantageously, the metal housing features a cable seal at its front end and / or a shaft seal at its rear end. This ensures that the cable and / or drive shaft exit the metal housing without water entering through these interfaces. For example, the cables can be routed from the metal tube using a suitable, tight-fitting screw connection. The use of a cable seal and / or a shaft seal allows the entire motor unit to be housed within the plastic casing in such a way that at least partial water flow around the metal housing is possible without water penetrating it.

[0037] Advantageously, the plastic housing features multiple flow channels. Having several flow channels on or within the plastic housing allows for more even and targeted water flow around the metal housing inside, resulting in improved cooling. Furthermore, this design ensures that frictional losses caused by water entering the plastic housing are distributed evenly. Consequently, this prevents unwanted roll, yaw, or pitch moments from being generated on the plastic housing during operation of the underwater propulsion unit.

[0038] Preferably, the flow channels of the plastic housing can have bulges on the plastic housing, thereby increasing the effective space between the plastic housing and the metal housing. This increases the flow of water to the metal housing and reduces the resulting pressure loss. Furthermore, the bulges can act as longitudinal flow deflectors, thus optimizing the stability of the underwater propulsion unit during operation.

[0039] Advantageously, the flow channels are separated from each other by longitudinal ribs, which also secure the metal and plastic housings together. This ensures that the metal housing is easily and securely positioned within the plastic housing. Furthermore, this design allows for the creation of defined flow channels, guaranteeing a predefined flow pattern around the metal housing. This optimizes the cooling of the metal housing during operation of the underwater unit. In other words, this reduces hydrodynamically induced flow losses during operation, thus enabling efficient cooling of the metal housing.

[0040] Advantageously, the flow channels each open into separate inlet and / or outlet openings in the plastic housing. This allows the inlet and / or outlet openings to be specifically adapted to the geometry of the respective flow channels. For example, the inlet openings can have a rectangular cross-section with rounded corners. Alternatively, the outlet openings can have a substantially oval cross-section. In this way, hydrodynamically induced flow losses during operation can be reduced, thus enabling efficient cooling of the metal housing.

[0041] According to an alternative embodiment, the flow channels open into common inlet distributors and / or outlet distributors with a common inlet or outlet opening. This further reduces hydrodynamically induced flow losses, thereby enabling efficient cooling of the metal housing.

[0042] Preferably, the metal housing is arranged substantially centrally within the plastic housing, the plastic housing preferably having a cable routing channel between the metal housing and the plastic housing. By arranging the metal housing substantially centrally within the plastic housing, it is possible to ensure that the flow channels can be arranged uniformly along the circumference of the plastic housing. Furthermore, this ensures that the metal housing is protected from all sides by the plastic housing against mechanical energy input, such as in the event of a collision or grounding.

[0043] Preferably, the openings and / or the flow channel have rigid or variable flow restrictors by means of which the flow rate through the flow channel can be adjusted. By using rigid or variable flow restrictors in the openings and / or the flow channel, a targeted supply of water flowing around the metal housing can be controlled. This allows the cooling of the metal housing to be varied not only depending on the velocity, but also via an additional adjustable parameter. As a result, the cooling of the metal housing and the drive components located within it can be further improved.

[0044] According to the invention, the openings and / or the flow channel have turbulators, the turbulators preferably being connected to the metal housing. Because the openings and / or the flow channel have turbulators, the heat transfer between the metal housing and the water flowing around it can be significantly improved. In other words, the turbulators increase the turbulent flow component, thereby promoting heat transfer. This is particularly true when the turbulators are connected to the metal housing. In this case, both the turbulent flow component in the fluid and the surface area of ​​the metal housing available for heat transfer are increased. Consequently, particularly efficient cooling of the metal housing can be achieved. According to an advantageous embodiment, the turbulators are designed such that the resulting pressure loss is as low as possible despite the generation of turbulence.This allows for efficient cooling without a noticeable impact on flow losses.

[0045] The underwater propulsion unit can, for example, be attached to the shaft of an electric outboard motor. On the top of the shaft, either a control unit with an integrated battery pack and tiller, or a control unit with a tiller but without its own battery pack, can be located. The outboard motor shaft itself can also consist of a simple metal or plastic tube enclosed in a plastic housing.

[0046] The underwater propulsion unit can also be arranged in a pod drive that is located exclusively underwater.

[0047] In a preferred embodiment, the shaft tube is directly connected to the metal housing, preferably welded and / or screwed and / or riveted to the metal housing and / or the shaft tube is formed in one piece with the metal housing.

[0048] The problem is further solved systemically with a system of at least two underwater drive units according to the present disclosure. The at least two underwater drive units of the system have an identical electric drive and / or an identical metal housing, wherein each electric drive is preset to a specific, different power class, and wherein at least one dimension of the plastic housing is selected depending on the preset power class.

[0049] In other words, the system is a product range or product portfolio. The individual, different performance classes can be adjusted to their respective performance levels, for example, via power electronics.

[0050] The use of identical electric drives and / or metal housings allows for the use of the same parts across different products, thus saving costs. By selecting at least one dimension of the plastic housing based on the preset performance class, necessary or advantageous adjustments can be made to the housing. Furthermore, this provides a visual distinguishing feature, allowing consumers to identify the preset performance class or visually differentiate between the various preset performance classes. This can lead to improved product marketing.

[0051] For the purposes of this disclosure, a preset performance class means a manufacturer-specified maximum performance limit that the end user cannot change at will without making extensive modifications to the underwater drive unit, such as by chip tuning or the like.

[0052] For example, at least two of the five power classes mentioned here can be preset, such as 0.2 to 0.7 hp, 1 to 3 hp, 1.5 to 3 hp, 5 to 20 hp, or 40 to 80 hp. Drives suitable for at least two of the mentioned power classes can have, for example, the same power electronics, the same metal housing, and the same electric drive. In particular, one of the possible power classes can then be set by adjusting the power electronics, for example, by flipping a switch or jumper, or by programming or uploading a drive control unit.

[0053] In other words, the same hardware can be used to provide drives of different performance classes. However, a differently designed plastic housing can be selected for each performance class, so that the size and shape of the housing can be adapted to the protection requirements, the necessary flow characteristics, and especially the heat dissipation needs of the respective performance class.

[0054] For example, a small crumple zone and low cooling capacity are sufficient for an underwater propulsion unit in the 0.2 to 0.7 hp class, allowing for a small plastic housing. However, an underwater propulsion unit in the 40-80 hp class requires a large crumple zone and high cooling capacity, necessitating a larger and, in particular, more robust plastic housing. Specifically, the wall thickness of the plastic housing can be increased. Furthermore, the flow characteristics of the 40-80 hp class plastic housing can be adapted to the higher achievable speed and acceleration.

[0055] Advantageously, the first underwater drive unit is preset to a higher performance class than the second underwater drive unit, with the plastic housing of the first underwater drive unit having a larger cross-section and / or a greater length than the plastic housing of the second underwater drive unit.

[0056] This ensures that the first underwater drive unit, with the higher performance class, has a locally increased distance between the plastic and metal housings, thus optimizing heat transfer between them. Ultimately, this improves the operational reliability of the underwater drive unit. It also results in the first underwater drive unit, with the higher performance class, appearing larger compared to the second underwater drive unit, providing a purely visual indication of its higher performance.

[0057] The task is further solved using a boat with an underwater propulsion unit. Brief description of the characters

[0058] Preferred further embodiments of the invention are explained in more detail by the following description of the figures. These show: Figure 1 is a schematic sectional view of a simplified underwater propulsion unit according to a first embodiment in a section plane extending along a longitudinal direction of the underwater propulsion unit; Figure 2 is a detailed sectional view of an underwater propulsion unit according to a further embodiment in a section plane extending along a longitudinal direction of the underwater propulsion unit; Figure 3 is a schematic sectional view of the underwater propulsion unit according to Figure 2 in a section plane oriented perpendicular to the longitudinal axis of the underwater drive unit; Figure 4 a schematic sectional view of the underwater drive unit according to a further embodiment in a section plane running along a longitudinal direction of the underwater drive unit; Figure 5 the underwater drive unit made of Figure 4in a perspective view; and Figure 6 a schematic view of an underwater propulsion unit in which the shaft tube is connected to the metal housing. Detailed description of preferred embodiments

[0059] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0060] In Figure 1Figure 1 shows a schematic sectional view of a simplified underwater drive unit 10 according to a first embodiment. The underwater drive unit 10 is depicted in a section plane extending along a longitudinal direction L of the underwater drive unit. The underwater drive unit 10 comprises a plastic housing 1 designed to be exposed to water flow and a metal housing 2 arranged in the plastic housing 1, in which an electric drive 3 is housed.

[0061] The metal housing 2 is waterproof and contains the electric drive 3. The metal housing 2 is completely enclosed within the plastic housing 1. Thus, a "shell-within-a-shell" principle is employed, namely a "metal housing-within-a-plastic housing" principle. The outer shell, the plastic housing 1, serves to optimize flow, as water flows around the plastic housing 1 during operation of the underwater drive unit 10. The inner shell, the metal housing 2, serves to cool the metal housing 2 and thus ultimately the electric drive 3. The metal housing 2 is untreated and was manufactured without any significant surface treatment.

[0062] The plastic housing 1 is connected to a shaft tube 6. The connection between the shaft tube 6 and the plastic housing 1 is made via a shaft tube protrusion 7. In this case, the shaft tube 6 does not need to be sealed. The underwater drive unit 10 can be connected to a boat (not shown) via the shaft tube 6. The propulsion of the underwater drive unit 10 is generated by an electric drive 3 driving a drive shaft 8 in the metal housing 2, to which a propeller 9 is mounted.

[0063] Figure 2Figure 1 shows a detailed sectional view of an underwater drive unit 10 according to a further embodiment in a section plane extending along a longitudinal direction of the underwater drive unit 10. The plastic housing 1 has openings 4 which are connected via a flow channel 5. The plastic housing 1 is designed such that, when the flow is around the plastic housing 1, the flow at least partially extends around the metal housing 2.

[0064] The openings 4 comprise an inlet opening 4' located in the front area of ​​the plastic housing 1 and an outlet opening 4" located in the rear area of ​​the plastic housing 1. The flow channel 5 extends between the inlet opening 4' and the outlet opening 4" essentially along a longitudinal axis L of the underwater drive unit 10.

[0065] The flow channel 5 of the underwater drive unit 10 is partially formed by the metal housing 2. This means that when water flows around the plastic housing 1, it enters the flow channel 5 through the inlet opening 4' and wets the metal housing 2. The heat transfer between the metal housing 2 and the surrounding water is facilitated by the water-metal housing contact surface pair. The metal housing 2 is watertight.

[0066] The plastic housing 1 is connected to a shaft tube 6. The connection between the shaft tube 6 and the plastic housing 1 is made via a shaft tube protrusion 7. In this case, the shaft tube 6 does not need to be sealed. The underwater drive unit 10 can be connected to a boat (not shown) via the shaft tube 6. The propulsion of the underwater drive unit 10 is generated by an electric drive 3 driving a drive shaft 8 in the metal housing 2, to which a propeller 9 is mounted.

[0067] The in Figure 2 The underwater drive unit 10 shown has two flow channels 5. Accordingly, the underwater drive unit 10 has two inlet openings 4' and two outlet openings 4". The inlet openings 4 and the outlet openings 4" are each designed as separate openings 4 in the plastic housing 1.

[0068] According to the illustration in Figure 2The metal housing 2 further comprises a metal tube 60, which includes a front tube seal 61 at its front end and a rear tube seal 62 at its rear end. The metal tube 60 is a simple, untreated metal tube. The front tube seal 61 and the rear tube seal 62 can each be considered a cap. These caps seal the metal tube 2 against water ingress. The caps can be connected to the metal tube 60 via screw connections, in particular via flanges, optionally with the addition of suitable gaskets. Furthermore, the metal housing 2 has a cable seal 63 at its front end and a shaft seal 64 at its rear end. In this specific embodiment, the cable seal 63 is arranged on the front tube seal 63, and the shaft seal 64 is arranged on the rear tube seal 62.

[0069] A cable 65 is guided from the metal housing 2 into the cable guide channel 50 via the cable seal 63, which is arranged in the front pipe seal 61 of the metal housing 3, and is sealed against water ingress. The cable 65 is then guided from the cable guide channel 50 into the shaft tube 6 at the shaft tube protrusion 7.

[0070] The electric drive 3 can comprise i) a motor, ii) a motor with a gearbox, iii) a motor with electronics and iv) a motor with gearbox and electronics.

[0071] Figure 3 shows a schematic sectional view of the underwater propulsion unit 10 according to the in Figure 2 The embodiment shown is in a section plane AA, which is oriented perpendicular to the longitudinal axis L and passes through the front pipe seal 61.

[0072] Therefore, in Figure 3The underwater drive unit 10 is shown, comprising a plastic housing 1 designed for water flow and a metal housing 2 arranged within the plastic housing 1, containing an electric drive (not shown). The plastic housing 1 has several flow channels 5, which are separated from each other by longitudinal ribs 20. The longitudinal ribs also fix the metal housing 2 and the plastic housing 1 to each other. The metal housing 2 is arranged essentially centrally within the plastic housing 1. Furthermore, the plastic housing 1 has a cable guide channel 50 between the metal housing 2 and the plastic housing 1.

[0073] The cable 65 is guided from the metal housing 2 into the cable guide channel 50 via the cable seal 63, which is located in the front pipe seal 61 of the metal housing 3, and is sealed against water ingress. The cable 65 is then guided from the cable guide channel 50 into the shaft tube 6 at the shaft tube protrusion 7.

[0074] Figure 4 Figure 1 shows a schematic sectional view of the underwater propulsion unit 10 according to a further embodiment in a section plane extending along the longitudinal direction 11. Accordingly, the figure from Figure 4An underwater propulsion unit 10 comprises a plastic housing 1 designed for water flow and a watertight metal housing 2 with an electric drive 3 arranged within the plastic housing 1. The plastic housing 1 has several flow channels 5, each running between separate inlet openings 4 and separate outlet openings 5. The plastic housing 1 is designed such that, when water flows around it, the metal housing 2 is at least partially surrounded by the flow. In this specific example, the flow around the metal housing 2 occurs through the flow through the individual flow channels 5. The respective flow channels 5 are partially formed by the metal housing 2. When water flows around the plastic housing 1, the flowing water wets the outside of the metal housing 2.

[0075] The plastic housing 1 is connected to a shaft tube 6, the connection being made via a shaft tube molding 7. The electric drive 3 of the underwater drive unit comprises an electric motor 31, a gearbox 30, and an electronic component, and drives a propeller (not shown) via a drive shaft 8.

[0076] The metal housing 2 of the underwater drive unit 10 has a cable seal 63 (not shown) at its front end for sealing a cable 65 and a shaft seal 64 at its rear end. The cable seal 63 is arranged on a front tube seal 61, which is located at a front end of the metal tube 60. The shaft seal 64 is arranged on a rear tube seal 62, which is located at a rear end of the metal tube 60.

[0077] The inlet openings 4' have a substantially rectangular cross-section with rounded edges. The outlet openings 4" have a substantially oval cross-section. This reduces hydrodynamically induced flow losses, thereby enabling efficient cooling of the metal housing 2.

[0078] Figure 5 The underwater propulsion unit 10 is shown. Figure 4 in a perspective view. This view shows that the individual flow channels 5 of the underwater propulsion unit have 10 protrusions. In other words, the plastic housing has 1 protrusion. The respective inlet openings 4' and outlet openings 4" are located at the beginning and end of each protrusion.

[0079] Figure 6 shows an underwater propulsion unit 10, similar to the variant from Figure 1The difference here is that the shaft tube 6 is directly connected to the metal housing 2. In the illustrated embodiment, the connection is provided by a weld 22 between the shaft tube 6 and the metal housing 2.

[0080] The direct connection between the shaft tube 6 and the metal housing 2 can also be achieved by screwing or riveting. In a further embodiment, the shaft tube 6 can be formed integrally with the metal housing 2.

[0081] In the aforementioned variants, the plastic housing 1 can also be connected to the shaft tube 6 - as in Figure 6 shown. A shaft tube forming 7 is also provided here, which serves to connect the plastic housing 1 with the shaft tube 6.

[0082] However, the plastic housing 1 can also be arranged without contact with the shaft tube 6 if there is a direct connection between the shaft tube 6 and the metal housing 2. For example, the shaft tube 6 can simply pass through an opening in the plastic housing 1.

[0083] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention. Reference symbol list

[0084] 1 Plastic housing 2 Metal housing 3 Electric drive 4 Openings 4 Inlet openings 4 Outlet openings 5 ​​Flow channel 6 Shaft tube 7 Shaft tube shaping 8 Drive shaft 9 Propeller 10 Underwater drive unit 20 Longitudinal ribs 22 Weld 30 Gearbox 31 Electric motor 50 Cable guide channel 60 Metal tube 61 Front tube seal 62 Rear tube seal 63 Cable seal 64 Shaft seal 65 Cable

Claims

1. Underwater propulsion unit (10), preferably for an outboard motor or a pod drive, comprising a plastic housing (1) configured for water to flow around and a metal housing (2) in which an electric drive (3) is accommodated, wherein the electric drive (3) is accommodated in the metal housing (2) so as to be sealed off from surroundings in a watertight manner and the metal housing (2) is arranged inside the plastic housing (1), wherein the plastic housing (1) has openings (4) which are connected via a flow channel (5), wherein the plastic housing (1) is configured such that, when water flows around the plastic housing (1), the water flows at least partially around the metal housing (2), wherein the openings (4) and / or the flow channel (5) have turbulators.

2. Underwater propulsion unit (10) according to claim 1, characterized in that the plastic housing (1) comprises an inlet opening (4') in a front region and an outlet opening (4") in a rear region, and the flow channel (5) extends along the longitudinal axis (L) of the underwater propulsion unit (10).

3. Underwater propulsion unit (10) according to claim 1 or 2, characterized in that the flow channel (5) is delimited at least partially by the metal housing (2).

4. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the plastic housing (1) is connected to a shaft tube (6), wherein the connection is preferably made via a shaft tube moulded-on portion (7).

5. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the electric drive (3) comprises an electric motor (31), an optional transmission (30) and / or an electronic component and drives a propeller (9) via a drive shaft (8).

6. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the metal housing (2) has a metal tube (60) which comprises a front tube seal (61) at a front end and / or a rear tube seal (62) at its rear end, wherein in particular the metal housing (2) has a cable seal (63) at its front end for sealing a cable (65) and / or a shaft seal (64) at its rear end.

7. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the plastic housing (1) has a plurality of flow channels (5).

8. Underwater propulsion unit (10) according to claim 7, characterized in that the flow channels (5) are separated from one another via longitudinal ribs (20), wherein the longitudinal ribs (20) further fix the metal housing (2) and the plastic housing (1) to one another.

9. Underwater propulsion unit (10) according to claim 7 or 8, characterized in that the flow channels (5) each open into separate inlet openings (4') and / or outlet openings (4") in the plastic housing (1).

10. Underwater propulsion unit (10) according to claim 7 or 8, characterized in that the flow channels (5) open into common inlet distributors and / or outlet distributors with a common inlet opening or outlet opening.

11. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the metal housing (2) is arranged substantially centrally in the plastic housing (1), wherein the plastic housing (1) preferably has a cable guide channel (50) between the metal housing (2) and the plastic housing (1).

12. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the openings (4) and / or the flow channel (5) have rigid or variable flow-limiting means, by means of which the flow through the flow channel (5) can be adjusted.

13. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the turbulators are preferably connected to the metal housing (2).

14. Underwater propulsion unit (10) according to one of the preceding claims, characterized in that the shaft tube (6) is connected directly to the metal housing (2), preferably is welded and / or screwed and / or riveted to the metal housing, and / or the shaft tube (6) is configured in one piece with the metal housing (2).

15. Boat having an underwater propulsion unit (10) according to one of the preceding claims 1 to 14.

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