DE102024121802B3 - Coupling device - Google Patents

Abstract

The present invention relates to a coupling device for compensating radial, axial, and/or angular positional deviations of connected, essentially coaxial shafts, in particular for connecting a turbine shaft to a generator shaft. The coupling device has diaphragm disks at opposite ends, each of which can be connected to the turbine shaft and the generator shaft. The coupling device is designed at least as a detachable, two-part shaft coupling, and at least one connection for a first coupling element and a second coupling element of the coupling device is formed by means of a first flange connection and a further non-positive connection. The present invention avoids the disadvantages of the prior art. In particular, the present invention provides a detachable and reproducibly precise connection of shafts. The simple assembly, disassembly, and alignment of the coupling device are a major advantage over known coupling devices. Furthermore, by distributing the torque between a flange connection and a further non-positive connection, a smaller, lighter design of the coupling can be achieved than with a coupling with only one flange.

Description

The present invention relates to a coupling device for compensating radial, axial and/or angular positional deviations of connected substantially coaxial shafts.

Coupling devices of the above-mentioned type are already known from the prior art.

The WO 01 / 46 563 A1 discloses a machine set, in particular a vertical hydropower machine set, in which the turbine shaft of a turbine is connected to the generator shaft of a generator. The machine set is intended to reduce the stress caused by alternating hydraulic forces exerted on the turbine. WO 01 / 46 563 A1 discloses a coupling between the turbine shaft and generator shaft that allows mobility perpendicular to the longitudinal axis to decouple the forces. This reduces the vibration stresses on the generator and relieves the load on the support structure in the generator area.

The DE 698 24 801 T2 relates to shafts for rotating electrical machines, particularly an improved composite shaft with a flexible double-diaphragm shaft. The new composite shaft incorporates a flexible disc shaft between two rigid shafts to tolerate larger misalignments. The composite shaft is intended for connecting turbomachinery to rotating electrical machines connected by a composite shaft.

The EP 0 211 090 A1 discloses a manufacturing process for a flexible coupling for torque transmission, known as a diaphragm coupling. EP 0 211 090 A1 Improves the connection between the diaphragm discs through a special electron beam welding zone, which minimizes alignment and balancing problems and withstands high mechanical loads. The diaphragm disc pairs can be used for various torque transmission devices and offer advantages such as vibration-free power transmission and maintenance-free operation.

The DE 43 04 611 A1 discloses a shaft coupling capable of compensating radial, axial, and angular misalignments of connected shafts. The coupling uses a flexible compensating element in the form of a tandem diaphragm, consisting of two disk- or ring-shaped diaphragms that are connected to each other. The diaphragms are firmly connected to each other at an outer peripheral area and connected to machine elements at their inner peripheral areas. DE 43 04 611 A1 The aim is to create a tandem diaphragm coupling that is as axially short as possible and allows for radial removal of parts of the coupling in the event of damage. The coupling offers simple assembly and replacement options, particularly thanks to an axially clampable clamping bush arrangement.

In particular, the coupling devices known from the state of the art often cannot transmit very high speeds (>90,000 rpm). Balancing long coupling devices is also difficult, and assembly and disassembly are not possible in a simple and reproducible manner.

It is therefore an object of the present invention to provide a coupling device that avoids the disadvantages of the aforementioned prior art. In particular, the present invention is intended to enable a detachable and reproducibly precise connection of shafts, torque transmission at very high speeds (>90,000 rpm), vibration-related decoupling of rotors, easy balancing of the device (balance quality min. G 2.5), and rotor-dynamic separation of the shafts.

This object is achieved by a coupling device according to the preamble of claim 1 in conjunction with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The present invention avoids the disadvantages of the prior art. In particular, the present invention provides a detachable and reproducibly precise connection of shafts. The simple assembly, disassembly, reassembly, and alignment of the coupling device are a major advantage over known coupling devices.

In addition, by dividing the torque between a flange connection and a cone/cone seat connection, a smaller and lighter design of the coupling can be achieved than with a coupling device with only one flange.

Since the separable shaft coupling can be connected to other coupling elements on the flange side, and the membrane discs can be removed from the respective shaft ends, it is recyclable in contrast to the state of the art, which means increased sustainability. To remove the respective coupling elements in the split state of the coupling device, the respective coupling flange can be used to attach a puller. This allows the shrunk-on diaphragm disc to be removed non-destructively and reusably from the shaft end of, for example, a turbine shaft or a generator shaft.

The coupling device according to the invention for compensating radial, axial, and/or angular positional deviations of connected, essentially coaxial shafts, in particular for connecting a turbine shaft to a generator shaft, provides that the coupling device has diaphragm disks at each distal end, which can each be connected to the turbine shaft and the generator shaft. The coupling device is detachably constructed in several parts, preferably two parts, and at least one connection for a first coupling element and a second coupling element of the multi-part coupling device is formed by means of a first flange connection and a further non-positive connection. The coupling device according to the invention is used, for example, to connect a turbine, in particular a gas turbine rotating at high speed, and a generator. The diaphragm disks at the opposite ends of the coupling device can be removably connected to the turbine and generator shafts in a non-destructive manner. The coupling device consists of at least two coupling elements that are rigidly coupled by means of a first flange connection and a further non-positive connection.

An advantageous development of the invention provides that the additional force-locking connection is designed as a cone-cone seat connection. A cone-cone seat connection is a force-locking connection. With this type of connection, the movement of the components is prevented by static friction. The hub does not slip as long as the load limit is not exceeded. Cone seat connections are suitable for transmitting large, alternating and shock-like torques. According to this development, the coupling represents a combination of cone-cone seat, flange coupling and double diaphragm. The cone-cone seat additionally contributes to the self-locking of the coupling assembly created from the two coupling elements and interacts with the flange connection. This combination enables slip-free torque transmission.

Furthermore, it is possible to balance the coupling device independently of the shafts to be connected. The connected coupling elements are balanced together. Since the coupling device can be precisely reassembled after disassembly and shrink-fitting the diaphragm discs onto the respective shaft ends to be connected, no rebalancing is required. The cone/cone seat connection enables precise reassembly.

Another advantageous embodiment of the invention provides that at least one of the two coupling elements is made of solid material, for example, a steel alloy. The end of the coupling element facing away from the diaphragm coupling can be machined from a solid cylinder to create a conical/truncated cone and/or a conical seat.

A further advantageous embodiment of the invention provides that at least one of the two coupling elements is designed as a hollow shaft. The hollow shaft can be manufactured as a cylindrical tube made of a metal alloy, the conical or truncated cone end and the conical seat end of which are manufactured using SLM (Selective Laser Melting) technology. To create the required surface finish, the cone or conical seat can subsequently be machined, for example, by cutting.

A combination of a hollow shaft coupling element and a coupling element made of solid material is also conceivable.

A further advantageous development of the invention provides that the diaphragm discs arranged at opposite ends of the coupling device have different diameters. The diaphragm discs in the coupling device can have different diameters in order to connect shafts with different diameters and/or materials.

Combinations of coupling elements of different lengths are also possible. This allows for compensation of different housing projections, for example, in turbine housings or generator housings. Furthermore, the center of gravity positions and natural frequencies of the coupling elements can be individually adjusted. A combination of coupling elements of different lengths is generally possible.

An advantageous development of the invention provides that each coupling end has a vertical diaphragm disk and, on the outer circumference of the diaphragm disk, a press fit that projects horizontally from the coupling device. The respective press fit serves for connection to a complementary shaft connection of a turbine or generator, onto which the press fit is shrunk. The vertical diaphragm disk is designed to be elastic, so that a rotational torque transmission is possible even with angular misalignment.

Another advantageous development of the invention provides that the coupling device can be balanced by removing or applying mass to the flange connection. This can be achieved, for example, by applying grub screws to the flange or by removing material from the flange screws.

The coupling device, for example, between a turbine shaft and a generator shaft, enables mobility perpendicular to the longitudinal axis and decouples the forces. This reduces, for example, the vibration stress on a generator and relieves the load on the support structure in the generator area. Furthermore, the coupling device is suitable for connecting air-bearing shafts.

Further measures improving the invention are described in more detail below together with the description of a preferred embodiment of the invention with reference to the figures.

• 1 eine schematische Ansicht einer erfindungsgemäßen Kupplungsvorrichtung;
• 2 eine schematische Ansicht des ersten Kupplungselements aus 1;
• 3 eine schematische Ansicht des zweiten Kupplungselements aus 1.

They show:

• 1 a schematic view of a coupling device according to the invention;
• 2 a schematic view of the first coupling element from 1 ;
• 3 a schematic view of the second coupling element from 1 .

The present invention will be further explained below using an embodiment together with the accompanying drawings. 1 shows a schematic view of an embodiment of a coupling device according to the invention. 2 shows a schematic view of the first coupling element from 1 and 3 shows a schematic view of the second coupling element from 1 .

The coupling device 1 according to the preferred embodiment as shown in 1 until 3 , comprises a first coupling element 2 and a second coupling element 3, each made of solid material, here, for example, a steel alloy with a chromium-molybdenum or chromium-nickel-molybdenum content. The two coupling elements 2, 3 are connected to each other at opposite ends 17, 18 in a reproducibly detachable and reconnectable manner.

The mutually facing ends 17, 18 of the first coupling element 2 and the second coupling element 3 each have a flange 6, 7. The first coupling element 2 has a flange 6 with threaded holes 11. The second coupling element 3 has a flange 7 with through holes 12.

In the present embodiment, two holes are distributed around the flange circumference. The screw connection is formed by two flange screws 8. Depending on the requirements, three, four, or five threaded holes 11, through holes 12, and flange screws 8 can also be provided.

By axially stopping between the flanges 6, 7, the screw connection can be relieved and/or the transmitted torque can be increased due to the friction generated.

Furthermore, in this exemplary embodiment, the first coupling element 2 has a conical, here frustoconical, projection that protrudes axially beyond the flange surface concentrically to the central axis of the first coupling element 2. The second coupling element 3 has a conical bore 10 formed concentrically to the central axis of the second coupling element 3, which begins at the flange surface and extends axially into the second coupling element 3.

The truncated cone has a slope or pitch of 3° to 15°, with the present one being 5°. The conical seat is congruent, i.e., designed to fit the truncated cone, with the truncated cone 9 slightly oversized compared to the conical bore 10 of the conical seat. The cone/conical seat connection ensures reproducible centering of the two coupling halves. This allows the two coupling elements 2, 3 to be precisely reassembled in the same position, thus avoiding the need for rebalancing.

The pitch and oversize of the truncated cone 9 define the torque that can be transmitted via the cone/truncated cone connection. The pitch of the truncated cone 9 also creates a self-locking effect when assembled.

The combination of flange and cone-cone seat connection achieves an optimal connection for transmitting torques at high speeds > 90,000 rpm with minimal slip, so that the split coupling device 1 behaves almost like a one-piece coupling device, but with the advantage of enabling non-destructive disassembly of the coupling device 1, including non-destructive removal of the reusable diaphragm discs 4, 5 from the respective (not shown) shaft ends.

In addition, the combination of the flange 6, 7 with the cone/cone seat connection allows a lower (partial) torque to be transmitted at the flange 6, 7, which means fewer flange screws 8 are required. By using fewer flange screws 8, additional weight on the flange 6, 7 can be saved and a negative impact on the imbalance can be avoided. By using fewer flange screws 8, there is more space on the flange for grub screws (not shown) for balancing. Furthermore, the grub screws can be used to press off the flange pairs when disassembling the coupling device 1 by screwing the grub screws in further, causing them to emerge on the inner flange side and press against the inside of the opposite flange.

In the present embodiment, for example, a transmittable torque of 3.7 Nm is achieved at 35 kW electrical power and a rotational frequency of 1500 Hz.

The cone-cone seat connection formed by the truncated cone 9 and the conical bore 10 and the flange connection complement each other as force-locking connections and establish a reproducibly detachable and reconnectable rigid connection of the two-part coupling device 1. This allows torques to be transmitted easily at very high speeds.

In the connected state, the two-part coupling device 1 has a first annular diaphragm disc 4 and a second annular diaphragm disc 5 at each of its distal ends. The first diaphragm disc 4 has a vertical section 13 and a press fit 14 projecting horizontally, i.e., axially parallel, outwards on the outer diameter of the vertical section 13. Furthermore, the second annular diaphragm disc 5 has a vertical section 15 and a press fit 16 projecting horizontally, i.e., axially parallel outwards.

In the present embodiment, the diaphragm disk 4 can be connected to a turbine shaft (not shown) via the press fit 14, for example, by thermal shrinking. The second diaphragm disk 5, in turn, can be connected to a generator shaft (not shown) via the press fit 16, for example, by thermal shrinking. The elasticity present in the diaphragm disks 4, 5 at both ends of the coupling device 1 allows radial, axial, or angular positional deviations to be compensated.

The stiffness of the diaphragm discs 4 and 5 allows the coupling's flexibility to be adjusted. This allows the generator shaft and the turbine shaft to be deformed or moved independently of each other. This also allows the turbine shaft and the generator shaft to be shortened, which increases the natural frequency of the individual shafts compared to long, rigid shafts.

In addition, the turbine shaft and the generator shaft are vibrationally decoupled by the coupling device 1, whereby there is almost no rotordynamic interaction.

wobei e_zul die zulässige Exzentrizität des Schwerpunktes in mm und ω die Bahngeschwindigkeit in rad/s ist.The coupling device 1 can also be easily balanced by removing material from the protruding threaded pins of the flange screws 8 or the screw heads of the flange screws 8. Alternatively or additionally, mass could be removed from the flange plates, or mass could be added through additional threaded holes and grub screws on the flange plates. This allows a balancing quality of greater than or equal to G 2.5 mm/s to be achieved. The balancing quality G in mm/s is a quality characteristic that enables the balancing comparison of rotors. In general, the heavier the rotor, the greater the permissible unbalance. The balancing quality G can be calculated as: $$\text{G}={\text{e}}_{\text{zul}}\cdot \mathrm{\omega }$$

where e _zul is the permissible eccentricity of the center of gravity in mm and ω is the orbital velocity in rad/s.

Furthermore, the coupling device 1, once balanced in the unassembled state, does not need to be rebalanced in the rotor assembly. This means that the first coupling element 2 and the second coupling element 3 are balanced while connected to each other. The coupling device 1 is then split, and the diaphragm discs 4, 5 are shrunk onto the respective shaft ends. Finally, the coupling device 1 is precisely reassembled without the need for rebalancing.

After connecting the first coupling element 2 to the second coupling element 3, the turbine shaft and the generator shaft remain dynamically decoupled. This means that the individual balancing qualities of the components to be connected are sufficient. This makes longer individual rotors possible, since, unlike a rigid coupling without a diaphragm, no problems arise due to natural frequencies.

The permanently active coupling device 1 allows for axial and radial positional deviations between the turbine shaft and the generator shaft, as well as for angular misalignment. The magnitude of this positional deviation is determined by the radial play in guide bearings adjacent to the coupling device 1 and serving to guide the turbine shaft and the generator shaft. The positional deviation can be in the range of a few micrometers to a few tenths of a millimeter and is suitable for the use of air bearings.

Thanks to the diaphragm disks 4, 5, radial deflections of the turbine shaft are not directly transmitted to the generator shaft, as is inevitably the case with rigid intermediate shafts. With the present invention, the forces acting in the radial direction are not transmitted to the generator shaft, or are transmitted only minimally, so that the load on the generator shaft is significantly reduced compared to a rigid intermediate shaft. This helps to relieve the load on the generator and a supporting structure in the generator area. In particular, an upper radial guide bearing is relieved. The basic idea behind the coupling arrangement is that the generator shaft is decoupled from the turbine shaft with regard to vibrations and positional deviations. The multi-part design allows for easy assembly, disassembly, and alignment of the coupling device.

The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of variants are conceivable, which utilize the presented solution even in fundamentally different designs. For example, a three-part coupling could be provided in which, for example, an additional spacer could facilitate assembly and disassembly if offsetting the shaft ends to be connected is difficult.

List of reference symbols

1

Coupling device

2

first coupling element

3

second coupling element

4

first membrane disc

5

second membrane disc

6

Flange with threaded hole

7

Flange with through hole

8

flange screw

9

truncated cone

10

tapered bore

11

threaded hole

12

through hole

13

vertical section

14

horizontal press fit

15

vertical section

16

horizontal press fit

17

End of first coupling element

18

End of second coupling element

19

distal end

20

distal end

Claims (9)

Coupling device (1) for compensating radial, axial and/or angular positional deviations of connected coaxial shafts, for connecting a turbine shaft to a generator shaft, wherein the coupling device (1) has membrane disks (4, 5) at opposite ends, which can each be connected to the turbine shaft and the generator shaft, wherein the coupling device (1) is designed at least as a detachable two-part shaft coupling, and wherein at least one connection for a first coupling element (2) and a second coupling element (3) of the coupling device (1) is designed by means of a first flange connection and a further non-positive connection. Coupling device (1) according to Claim 1 , whereby the further force-locking connection is designed as a cone-cone seat connection. Coupling device (1) according to Claim 1 or 2 , wherein at least one of the two coupling elements (2, 3) is made of solid material. Coupling device (1) according to Claim 1 or 2 , wherein at least one of the two coupling elements (2, 3) is designed as a hollow shaft. Coupling device (1) according to one of the preceding claims, wherein the membrane discs (4, 5) arranged at opposite ends of the coupling device (1) have different diameters. Coupling device (1) according to one of the preceding claims, wherein each coupling end has a vertical diaphragm disc (4, 5) and, on the outer circumference of the diaphragm disc (4, 5), a press fit (14, 16) projecting from the coupling device (1) parallel to the coupling axis. Coupling device (1) according to one of the preceding claims, wherein the length of the first coupling element (2) with the first diaphragm disc (4) is shorter than the length of the second coupling element (3) with the second diaphragm disc (5). Coupling device (1) according to Claim 5 , 6 or 7 , wherein the first membrane disc (4) of the first coupling element (2) has a smaller diameter than the second membrane disc (5) of the second coupling element (3). Coupling device (1) according to one of the preceding claims, wherein the coupling device (1) can be balanced by mass removal or mass application at the first flange connection.

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