EP2238019B1 - Electric engine for a ship - Google Patents

Abstract

The invention relates to a drive for a watercraft comprising a) a rotating unit provided with a propeller; b) an electric motor provided with a coaxial arrangement of rotors and stators and a radially oriented magnetic field, said rotor being arranged on the outside of the body of the watercraft and being non-rotationally connected to the propeller; c) an air gap between the rotor and the stator is flooded and the rotor and/or the stator are encapsulated in a water-tight manner and d) when seen in the axial direction, water-lubricated friction bearings that at least radially support said rotating unit are arranged on both sides of the air gap.

Description

The invention relates to a drive for a watercraft, in particular a pod drive or a drive for an underwater vehicle.

Drives for underwater vehicles with housed outside the pressure shell electric motors are known. For this purpose, for example, on the US 5509830 directed. Such a design allows the waiver of a passage for a drive shaft through the pressure shell, so that the drive can be configured without pressure-resistant seals. Moreover, the vibration and noise problems associated with such driveshaft penetrations do not occur. In addition, on the US 5,607,329 A directed.

Another application example is pod ship propulsion systems, for which an electric propulsion engine is housed in a nacelle hinged to a ship's hull. The energy for operating the outside-mounted engine is usually generated by means of a diesel generator, which is housed in a suitable location in the ship's hull.

Pod marine propulsion systems have a number of advantages over conventional propulsion systems. This is on the one hand, the connection of an effective propulsion system with a control unit, resulting from the rotation of pod ship propulsion relative to the ship's longitudinal axis. This circumstance is particularly important for ferries and icebreakers. In addition, pod ship propulsion engines are characterized by a reduced noise within the hull and lower vibration tendency. Furthermore, additional space is created in the hull by displacing at least parts of the drive to the outside. Due to the above advantages, pod ship propulsion systems, especially for cruise liners, in which, in addition to the high Eigenmanövrierfähigkeit high comfort for the passengers, enforced.

The US 2714866 discloses a design of a pod ship propulsion with a Frischwasserumströmten electric motor with coaxial arrangement of rotor and stator. The radially inner rotor is rotationally rigidly connected to a hollow shaft, which cooperates via a coupling with a coaxially disposed within the hollow shaft drive shaft of the propeller. Due to the intermediate coupling, the construction is expensive, in addition, the drive shaft of the propeller is supported by radial bearings with a relatively small diameter.

Another embodiment of a pod ship propulsion is from the DE 102004048754 A1 known. Described is a pod ship propulsion with high efficiency, wherein a slow-running, large-scale propeller is driven by a high-speed electric motor via an intermediate hydrodynamic power split transmission. This measure creates an energy-efficient drive system, which, however, is structurally complex.

Alternatively, generic direct drives without intermediary gearboxes have therefore been proposed which use high-pole, large-building electric motors. One possible embodiment is to design the rotor of an electric motor as an external rotor and to connect it torsionally rigid with a propeller in a rotating unit. For example, on the by the DE 3141339 A1 disclosed drive for an underwater vehicle.

This results in a drive, in which the stator of an electric motor is housed in a circumferential groove of a cylindrical portion of the vehicle body. The rotor of the electric motor is placed in the hub of a rotating unit, which simultaneously carries the propeller. The air gap between the rotor and the stator is flooded with water. To run the revolving unit rolling bearings are provided, wherein the bearing shells are attached to the axial side surfaces of the rotating unit, or the circumferential groove for receiving the stator. With such a bearing arrangement tilting moments on the propeller, which change the airgap dimensions, are difficult to intercept. In addition, rolling bearings are problematic in terms of limited surface pressures and resistance to sediment contamination. In addition, such bearings can absorb shock and vibration only to a limited extent, or they allow only minor deformation.

For constructive improvement of the drive were therefore in the cited document DE 3141339 A1 discloses electric drives in the form of disc motors. Here, tilting moments are supported on the rotating unit by magnetic forces at the air gap of the electric motor. A corresponding construction is from the EP 1140618 A1 known. The disadvantage, however, is that the static and dynamic loads emanating from the propeller act directly on the air gap tolerances of the disc motor and thus influence its power output. Furthermore, bearings of such disk motor arrangements are offset radially inward due to the radial extent of the rotor disk, so that as the bearing circumference increases, the surface pressures in the bearing increase.

The invention has for its object to provide a drive for a watercraft, which overcomes the disadvantages set out above. What is needed is a transmission-free direct drive, which leads to a structurally simplified and yet stable generic ship propulsion and whose large-sized electric motor provides an efficient drive for a slowly revolving propeller.

The object is solved by the features of the independent claim. Accordingly, the drive according to the invention for a watercraft comprises a revolving unit, which additionally carries the rotor of an electric motor in addition to the propeller, so that there is a rotationally fixed connection between the rotor and the propeller. The electric motor has a coaxial arrangement of rotor and stator and a radially directed magnetic field in the air gap between Rotor and stator on. The stator is housed either in an air gap pointing portion of the hull of the vessel or in a hinged to the hull of the vessel gondola housing a pod drive. Preference is given to a radially large-sized generator having a plurality of poles.

The air gap between the rotor and the stator is flooded, in which area either ambient water, preferably filtered, or fresh water is supplied. For separation from the water-filled air gap, the stator cladding is preferably encapsulated waterproof. This is achieved either by a can of austenitic steel or another non-electrically conductive material. For this purpose, inter alia, a glass or carbon fiber reinforced material or an elastomer in question. Alternatively, the seal can be done by a potting compound.

In the event that a volume area is sealed off to seal the stator, a pressure compensation vessel is preferably provided for this area. According to the stator, the rotor is encapsulated, as far as this is not carried out purely passive with permanent magnets. This therefore relates to embodiments with external excitation, in which case the energy required for the external excitation preferably is transmitted without contact, in particular inductively, across the air gap.

According to the invention, at least one water lubricated sliding bearing is arranged for supporting the rotating unit in the axial direction on both sides of the air gap, which is designed and oriented such that at least one support takes place in the radial direction for the revolving unit. The water-lubricated sliding bearings lead to a variety of advantages, on the one hand they are characterized by a high load capacity and a high resistance to contamination and the ingress of sediments. In addition, they tolerate to some extent structural deformations, especially when using a hard-soft mating, and thus can absorb vibrations and shocks.

Furthermore, the water-lubricated slide bearings used in the invention are inexpensive and can be constructed of individual segments, which in turn are separately exchangeable.

The water-lubricated plain bearings used according to the invention for the axial support of the rotating unit allow safe guidance even for high-performance drives. In addition, it is preferable to provide an additional, separately applied thrust bearing for the large thrust washers which is likewise designed as a water-lubricated sliding bearing, again in particular in the form of a hard-soft pairing for the bearing surfaces. Further, a segmented design of the sliding bearing is preferred, so that when worn individual components can be replaced. It also simplifies the assembly and adjustment of the plain bearing.

For a further development of the invention, the region of the circulating unit, which serves to support the propeller, is axially spaced from that region in which the rotor is arranged and on which the water-lubricated plain bearings are provided for radial support. Furthermore, the thrust bearing is designed to intercept the propeller thrust as close as possible to the point of introduction of the propeller forces. The further design is advantageous because the propeller forces and the associated deformations are kept as far as possible from the rotor and its storage, thereby remain largely constant during operation, the air gap tolerances, so that unwanted fluctuations in the drive power can be avoided.

In order to implement the preferred spacing of the propeller relative to the plain bearings arranged in the axial direction on both sides of the air gap, a hub disc is provided, which carries the propeller and which is rotationally rigidly connected to the part of the revolving unit which carries the rotor. This part can be cylindrical or hollow cylindrical.

According to the invention, the rotor is designed as an internal rotor. Accordingly, the rotating unit comprises a rotor supporting or receiving part, which is inserted into a recess in that part of the ship's hull or the nacelle, which serves to receive the stator (fixed part) is inserted. Subsequently, this is referred to as a support body. Accordingly, the support body runs through the water-lubricated plain bearings on both sides of the air gap on the inner wall of the recess in the fixed part.

A particular advantage of this embodiment is the fact that the support body for receiving and / or for supporting the rotor may have a separate buoyancy volume, for example, by a voluminous, watertight executed embodiment or by separate buoyancy bodies. Due to the buoyancy volume, the water-lubricated plain bearings on both sides of the air gap can be relieved and / or the rotating unit is balanced so that a defined preload of the bearings is made. As a result, especially when starting the area of mixed friction in the camps go through quickly.

Figur 1

zeigt einen erfindungsgemäßen Antrieb im Axialschnitt, wobei der Rotor als Innenläufer ausgebildet ist.

The invention will be explained in more detail below with reference to an embodiment in conjunction with a figure representations. In this is shown in detail:

FIG. 1

shows a drive according to the invention in axial section, wherein the rotor is designed as an internal rotor.

FIG. 1 shows schematically simplified a preferred embodiment of the invention in longitudinal section along the axis of rotation 17. Shown is a revolving unit 1, comprising a propeller 2, which is supported by a hub disc 15. An additional part of the rotating unit 1 is the hood 14, which is designed aerodynamically.

The rotor 4 of the electric motor 3 is part of the rotating unit and is arranged coaxially with the stator 5, which is housed in a fixed part 16. The fixed part may be either a gondola housing of a pod ship drive rotatably hinged to a ship's hull, or a part of the ship hull itself, such as the stern area of an underwater vehicle.

On both sides of the air gap 11, a first water-lubricated sliding bearing 12.1 and a second water-lubricated sliding bearing 12.2 is provided for the expiry of the rotating unit 1 on the fixed part 16. For the present embodiment, these water-lubricated plain bearings 12.1, 12.2 are designed as radial bearings. Further embodiments, such as a combination of radial and axial bearings, are conceivable. For the illustrated preferred embodiment, however, a separate thrust bearing 13 is provided to intercept the thrust forces of the propeller 2, which is mounted as possible propellemah. In the present case, the support is made on a flange 19 connected to the fixed part 16, wherein the separate thrust bearing 13 double-acting is formed and traction / thrust loads of the propeller 2 traps in the axial direction.

The water-lubricated plain bearings 12.1, 12.2 used according to the invention and the correspondingly designed separate axial bearings 13 are preferably segmented and designed as a hard-soft pairing. This results in bearings with high load capacity, which are insensitive to penetrating sediments. In addition, the bearings are inexpensive and can safely intercept the forces and moments even for drives with high performance in the range of a few megawatts. Furthermore, the bearings spring safely from a certain inherent elasticity shocks. That is, they are deformable to some extent. However, only so far as the necessary tolerances of the air gap 11 for the electric motor 3 can be safely met.

The electric motor 3 has a watertight encapsulation, in particular of the plated areas. For this purpose, a abgekapseiter stator 8 is provided to protect the stator. For the illustrated embodiment, a rotor 4 is selected with external excitation, so that on the rotor side an encapsulated rotor region 7 is present. For external excitation, a unit for contactless energy transfer 6 is provided for supplying the energy required for the external excitation from the existing part 16 to the circulating unit 1. This can be designed as an annular coil arrangement for inductive energy transmission or as an exciter machine. The details of the embodiment are not shown in the figures.

For the embodiment of the encapsulated rotor region 7 and the encapsulated stator region 8, different embodiments are conceivable, for example the use of a split tube or the use of casting compounds for watertight encapsulation. For the illustrated embodiment, the encapsulated area in the rotating unit, the encapsulated rotor portion 7, by an at least partially elastic material made of fiberglass from water-filled area of the air gap 11 separately. For pressure equalization of the encapsulated rotor portion 7, a pressure compensation vessel 9 is provided.

The rotor 4 is designed as an internal rotor. Accordingly, the rotor-carrying part 10 of the rotating unit 1 is formed as a support body 18 which receives or supports the rotor 4. This support member 18 is inserted into a recess in the fixed part 16 and is supported by means of the water-lubricated plain bearings 12.1, 12.2 in the radial direction against the inner wall of this recess in the fixed part 16 from.

An advantage resulting from an embodiment with a rotor as an internal rotor can be seen in the fact that the support body 18 introduced into the recess in the stationary part 16 can be provided with its own buoyancy volume. This is achieved in that at least parts of this supporting body 18 are sealed and hollow or formed with a buoyant material. For this purpose, a cylindrical or hollow cylindrical design comes into question. By the buoyancy forces, the weight of the rotating unit 1 is at least partially compensated. This results in a relief of asymmetric, static bearing forces in the water-lubricated plain bearings 12.1, 12.2, so that in particular improves the slow-speed behavior.

In addition, by balancing the rotating unit by appropriate choice of the buoyancy forces of the hood 14, the hub disc 15 and the support body 18, the relative position of the lifting point and the center of gravity of the rotating unit 2 and the size of the resulting torque can be adjusted so that the lubricated sliding bearings 12.1, 12.2 are defined to be biased and so bearing vibrations be damped. Furthermore, the mixed friction phase is traversed faster at low speeds.

In the figure representation, the arranged in the axial direction on both sides of the air gap, water-lubricated plain bearings 12.1, 12.2 are arranged substantially on the predetermined by the air gap 11 radius. This represents a preferred embodiment, since in this way radially bulky bearings arise with correspondingly reduced surface pressure. However, embodiments are conceivable in which the water-lubricated slide bearings 12.1, 12.2 are arranged on a deviating from the air gap 11 radius. It is thus possible, for structural reasons, to set the water-lubricated slide bearings 12.1, 12.2 to an even larger or even to a reduced diameter.

Further embodiments of the invention are conceivable within the scope of the following claims. Thus, an inventive drive more than comprise a propeller, it is conceivable in particular for a pod ship propulsion that a pulling and pushing propeller are mounted on both sides of a nacelle, and it is conceivable that each propeller is driven by a separate electric motor or drive multiple propellers with an electric motor.

Claims (9)

1. A drive unit for a watercraft, including

   1.1 a rotatable gondola, steerable with respect to a ship hull;

   1.2 a rotating unit (1) with a propeller (2);

   1.3 an electric motor (3) with a coaxial arrangement of rotor (4) and stator (5) and a radially-oriented magnetic field, whereas the rotor (4) is designed as an internal rotor and is connected in a torsionally rigid manner to the propeller (2);

   1.4 whereas the stator (5) is received in the gondola and the rotor (4) is carried by a supporting body (18), which is inserted into a recess in the gondola as a part of the rotating unit (1); and

   1.5 the air gap (11) between the rotor (4) and the stator (5) is flooded, whereas the rotor (4) and/or the stator (5) are encapsulated in a watertight manner;
   and

   1.6 water-lubricated slide bearings (12.1, 12.2) are arranged, seen in axial direction, on both sides of the air gap (11), bearings by means of which the supporting body (18) rotates against the inside wall of the recess in the gondola; and

   1.7 the supporting body (18) has a separate buoyancy volume for relieving and/or balancing the water lubricated slide bearings (12.1, 12.2).
2. The drive unit of claim 1, characterised in that the separate buoyancy volume is formed of hollow and sealed parts of the supporting body (18) and/or of buoyant materials on the supporting body (18).
3. The drive unit of claim 1 or 2, characterised in that the propeller (2) is axially spaced apart from the slide bearings (12.1,12.2) arranged on both sides of the air gap (11).
4. The drive unit of claim 3, characterised in that the propeller (2) is carried by a hub disc (15), which is connected in a torsionally rigid manner to a rotor-carrying part (10) of the rotating unit (1).
5. The drive unit according to any of the preceding claims, characterised in that a separate axial bearing (13) is provided for the rotating unit (1), which is designed as a water lubricated slide bearing.
6. The drive unit of claim 5, characterised in that the separate axial bearing (13) of the rotating unit (1), seen in axial direction, is arranged between the propeller and the rotor.
7. The drive unit according to any of the preceding claims, characterised in that the rotor (4) and/or the stator (5) are encapsulated in a watertight manner by a can made of a non electrically-conducting material or of a casting compound.
8. The drive unit according to at least one of the preceding claims, characterised in that a pressure compensation vessel is allocated to the rotor (4) and/or stator (5) which is encapsulated in a watertight manner.
9. The application of a drive unit according to one of the previous claims for a pod ship drive unit and/or for driving a submersible.

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