Planetary gear with sun wheel mounted in planetary carrier

Description

[0001] The invention relates to a planetary gear for a wind turbine driven by a rotor, comprising at least one planetary stage rotating about an axis of rotation AD in a gear housing, wherein the at least one planetary stage has a planet carrier and a ring gear, and the planet carrier is at least indirectly connected to the rotor for drive purposes, and wherein the planet carrier has several planet gears rotating with the planet carrier and engaging alternately with the ring gear and a sun gear.

[0002] The drivetrain of a wind turbine is configured such that the rotor drives a main shaft supported in a main bearing unit. The main shaft is connected to a gearbox, typically a planetary gearbox, which in turn drives a generator unit. The planetary gearbox comprises at least one planetary stage, with the main shaft generally driving the planet carrier of the at least one planetary stage and the output driven towards the generator via the sun gear of the planetary stage. The gearing of the planetary stages is helical. Regarding the drivetrain's bearing arrangement, a distinction must be made between the main shaft's support via the main bearing unit and the bearing support for the axial force acting in the at least one planetary stage. This axial force arises from the helical gearing of the gear components or from the component of gravity acting downhill due to the inclined gearbox.The specific storage method can vary depending on the application.

[0003] This section considers the application of the main bearing unit where the main shaft is rigidly connected to the planet carrier of at least one planetary stage, and the planet carrier has no independent bearing relative to the gearbox housing. Instead, the main shaft, via the main bearing unit, ensures the precise and angular positioning of the first planet carrier within the gearbox housing. The axial force that must be supported due to the helical gearing or the force of gravity acting downhill is directed towards the generator in the normal direction of rotation of the rotor, i.e., in the so-called nominal operation, and only reverses its direction in the rare case of reverse rotor rotation. When considering the planet carrier of a planetary stage, no free forces act on the planet carrier; that is, the sum of the forces acting on the planet carrier is zero.This means, however, that the axial force resulting from the helical gearing or the force of gravity acting downhill acts on the sun gear of the planetary stage, and the sun gear must be adequately axially supported. This axial force is conventionally supported by radially projecting support flanges and corresponding bearings within the gearbox housing. Particularly when a second, subsequent planetary stage is provided, the sun gear of the first planetary stage is drivenly connected to the planet carrier of the second planetary stage, and the axial force is supported, i.e., transferred into the gearbox housing, via a support flange located behind the second planetary stage during nominal operation and via a support flange located between the two planetary stages during reversing operation. Each support flange must be dimensioned to absorb the axial force and consequently contributes to the weight of the gearbox housing and its axial installation space.Furthermore, the axial force is transmitted via rotating components of the planetary stages, meaning these must also be appropriately dimensioned, which increases both weight and installation space. Consequently, there is a constant need to reduce the installation space and weight of support flanges, or even to eliminate them entirely.

[0004] CN 211 314 459 U discloses a multi-stage planetary gear in which the second planet carrier is designed as a stationary housing component. The second ring gear is rotatably mounted, and the second planet gears are statically arranged. The first sun gear is rotationally fixed and integrally formed with the third planet carrier, this unit being rotatably mounted relative to the first planet carrier via a bearing. US 6 907 951 B2 discloses a single-stage planetary gear in which the sun gear is integrally formed with the input / output shaft, and this unit is rotatably mounted relative to both the gear housing and the planet carrier.

[0005] The object of the invention is to demonstrate measures that influence the axial force in its direction and course in such a way that support flanges can be designed to reduce weight and installation space.

[0006] The problem is solved by a planetary gear unit having the features of claim 1. Preferred embodiments are specified in the dependent claims and the following description.

[0007] The invention relates to a planetary gear for a rotor-driven wind turbine with at least one first and at least one second planetary stage arranged in a gearbox housing about an axis of rotation, wherein the first planetary stage has a planet carrier and a ring gear and the planet carrier is suitable for at least an indirect drive connection with the rotor and wherein the planet carrier has several planet gears rotating with the planet carrier and alternatingly meshing with the ring gear and a sun gear, wherein the sun gear is rotatably mounted about the axis of rotation and axially supported relative to the planet carrier of the first planetary stage by means of a bearing and a planet carrier of the second planetary stage is rotatably mounted relative to the planet carrier of the first planetary stage by means of a bearing implemented as a rolling bearing.

[0008] The planetary gear set can comprise one or more planetary stages. The last planetary stage can drive a generator directly or indirectly. In the case of an indirect drive, an intermediate spur gear stage may be provided. The planet carrier can be cage-like. The axis of rotation AD, around which the at least one planetary stage rotates during operation, defines the axial direction.

[0009] The planet gears are held on the planet carrier by planet shafts. The planet shafts run parallel to and offset from the axis of rotation AD. The planet gears are freed from the planet carrier or the side plates in a radial direction inwards and a radial direction outwards and mesh with a ring gear and a sun gear or a sun gear shaft via helical gear teeth.

[0010] The sun gear can be mounted directly opposite or on the planet carrier. The planet carrier can provide a suitable area for this purpose, which is appropriate for arranging such a bearing. Alternatively, the sun gear can also be mounted indirectly on the planet carrier, for example, by having the sun gear sit directly on a driven element, which in turn is mounted directly on the planet carrier. A driven element can be, for example, an output shaft that transmits the torque to be transferred to a further gear stage. If the further gear stage is a second planetary gear stage, the output shaft can be designed as the planet carrier.

[0011] By mounting the sun gear axially opposite or on the planet carrier, the axial force introduced into the sun gear via the helical gearing, or the force of gravity induced by the incline – for simplicity, only the axial force will be referred to hereafter – can be transferred into the planet carrier of at least one planetary stage, so that the axial force does not act on downstream parts of the planetary gear set. Within the planetary stage, the sun gear is axially supported against the planet carrier. This means that the axial force acting on the sun gear of a first planetary stage is not to be transmitted through and supported by any subsequent planetary stage or spur gear set. The described bearing concept, namely sun gear on planet carrier within a planetary stage, can be described as a rotating-within-a-rotating bearing. Such a bearing is, among other things,This design is advantageous for wear behavior because both the outer and inner bearing elements rotate, and the axial force is not transferred via a stationary area, as is the case with bearings supported by flanges of the gearbox housing. The speed difference in downstream parts of the planetary gearbox is also reduced by a factor of the first planetary stage.

[0012] By eliminating the need to transfer the axial force via a support flange on the gearbox housing, existing support flanges can either be made smaller, as they no longer require increased axial stiffness, or even omitted entirely. This saves space and weight within the gearbox housing. The axial force transmitted from the sun gear to the planet carrier during nominal or reversing operation is supported via the main shaft in the main bearing unit.

[0013] According to the invention, the bearing is implemented as a rolling bearing.

[0014] In contrast to a bearing in the conventional arrangement in a housing-fixed support flange, the rotating-in-rotating bearing has a low circumferential load and a low rotational speed.

[0015] According to the invention, the bearing is arranged within the sun gear. This makes it possible, in particular, to reduce the diameter of the bearing point between the sun gear and the planet carrier compared to a bearing in a support flange.

[0016] In a further preferred embodiment, the gear mesh is helical, with the gearing having a right-hand or left-hand helix direction. In this configuration, the axial force acting during nominal operation due to the helical gearing or the force of gravity is directed towards the generator. In this configuration, the direction of the helical gearing is reversed, and during nominal operation, the axial force is directed towards the rotor. As a result, during nominal operation, the axial force acting due to the helical gearing opposes the axial force introduced into the main shaft by the rotor, thus reducing the total axial force acting in the main shaft. The axial force generated by the helical gearing and directed towards the rotor by reversing the helix direction therefore relieves the load on the main bearing assembly.

[0017] In a preferred embodiment of the planet carrier, the sun gear is at least indirectly supported on an axially oriented bearing flange of the planet carrier. This bearing flange, along with its connection to the rest of the planet carrier's structure, allows for a significantly more torsionally rigid design. In a specific embodiment, the bearing flange may be integrally formed with the planet carrier or, as a ring-shaped component, form a functional unit connected to the planet carrier.

[0018] In the inventive embodiment of the planetary gear, in which at least a second planetary stage with a planet carrier is provided and the planet carrier of the second planetary stage is rotatably mounted relative to the planet carrier of the first planetary stage via the bearing, structural and design advantages arise due to a rotating-within-rotating mounting of the sun gear relative to the planet carrier in the first planetary stage. Conventionally, the axial force acting on the sun gear is directed towards the generator and is guided from the sun gear via the planet carrier of the second planetary stage and introduced behind the second planetary stage via a bearing into a support flange.However, by incorporating a rotating-within-rotating bearing for the sun gear relative to the planet carrier in the first planetary stage, the axial force is no longer transmitted via the second planetary stage. This allows the support flange behind the second planetary stage to be eliminated or reduced in size, thus saving space and weight. Furthermore, the rotating-within-rotating bearing also eliminates the need for the support flange conventionally located between the first and second planetary stages. This support flange is traditionally designed to counteract the axial force generated during rotor reversal. Now, the axial force during reversal is also transmitted via the planet carrier of the first planetary stage to the main bearing unit and counteracted by it.Another advantage is that the gear elements, which are relieved of axial force by the modified bearing arrangement, can align themselves better during operation and can also be made narrower overall. In summary, this preferred design allows for a significantly shorter planetary gear set, as it saves space between the two planetary stages and behind the second planetary stage. Furthermore, the planet carrier of the second planetary stage can be made with a single side, since it no longer has to withstand the load from the axial force.

[0019] In one specific embodiment, the planet carrier of the second planetary stage is connected to the sun gear of the first planetary stage in a rotationally fixed and axially load-bearing manner. Based on this, the first possible design configuration is that the bearing of the rotating-in-rotating bearing arrangement is located between the first planet carrier and the first sun gear, and the second possible design configuration is that the bearing of the rotating-in-rotating bearing arrangement is located between the first and second planet carriers. In the second design configuration, it can be provided, in particular, that the bearing is located in an axial area formed by an axially overlapping arrangement of the bearing flange of the first planet carrier with a hub of the second planet carrier.

[0020] In a preferred embodiment, the sun gear of the first planetary stage can be held rotationally fixed on the hub of the second planetary carrier by means of a gear pairing around its circumference. This advantageously allows the first and second planetary stages to be positioned closer together axially. The sun gear of the first planetary stage can also be axially connected to the second planetary carrier.

[0021] In another possible embodiment of the planetary gear set, a second rolling bearing can be provided, via which the second planet carrier is rotatably mounted on the side facing away from the first planetary stage relative to the gear housing. This embodiment is particularly advantageous if the planetary gear set includes a third planetary stage and the axial force generated during reversing operation of the rotor in the third planetary stage must be supported by a support flange between the second and third planetary stages. In this case, this support flange can be used to mount the planet carrier of the second planetary stage, thus creating a four-point mounting together with the rolling bearing between the sun gear and the planet carrier of the first planetary stage.

[0022] The problem is also solved by a drive train for a wind turbine for the torque-transmitting connection of a rotor with a generator, comprising a main bearing unit with a bearing housing and a main shaft and a gearbox driven via the main shaft, wherein the gearbox drives the generator at least indirectly and the gearbox is designed as a planetary gearbox according to one of the described embodiments.

[0023] The problem is solved in the same way by a wind turbine with a rotor flange with a rotor and a generator, wherein a drive train held on a machine carrier and connecting the rotor flange to the generator is provided and the drive train is designed as described above.

[0024] The invention is explained below by way of example with reference to the accompanying drawings and preferred embodiments. The drawings show: Fig. 1 : a schematic representation of a wind turbine that does not fall under the wording of claim 1, Fig. 2 : a gearbox designed as a planetary gearbox for a wind turbine, which does not fall under the wording of claim 1, Fig. 3 : a section of a planetary gear in a possible design with rotating-in-rotating bearing; Fig. 4 : a section of a planetary gear in a possible design with rotating-in-rotating bearing; Fig. 5 : a section of a planetary gear in a possible design with rotating-in-rotating bearing and Fig. 6a) - 6c): axial forces generated via the helical gearing of the first planetary stage.

[0025] The Figure 1Figure 1 shows a schematic representation, not to scale, of a possible configuration of a wind turbine 100. The essential element of the wind turbine 100 is a drive train 102, which in this case structurally comprises a rotor flange 104 with a rotor 106, a main bearing unit 108, a gearbox 10, and a generator 112. At least the main bearing unit 108 and the generator 112 are supported by a tower 116 against a ground (not shown) via a machine carrier 114. The main bearing unit 108 comprises a main shaft 118, which is rotatably mounted about an axis of rotation AD relative to a bearing housing 120 of the main bearing unit 108 via an angled tapered roller bearing. The rotor flange 104 is held at one end of the main shaft 118, and the rotor 106 is held to the flange. The other end of the main shaft 118 is rigidly connected to the gearbox 10 in order to introduce a drive torque applied by the rotor 106 into the gearbox 10.The gearbox 10 is designed as a planetary gearbox with one or more planetary stages. The gearbox 10 is driven by a generator shaft 124 and connected to the generator 112. The bearing housing 120 is connected to the gearbox 10 via a flange 126. A reaction torque of the gearbox 10 is supported against the machine support 114 via the flange 126.

[0026] The Figure 2 shows a gearbox designed as a planetary gearbox 10, as is used, for example, in a Figure 1The planetary gear 10 can be installed in the depicted wind turbine 100. The planetary gear 10 comprises three planetary stages 14 1 to 14 3 arranged in series, which are arranged rotating around an axis of rotation AD in a gear housing 12. Apart from its dimensions, each planetary stage 14 1 to 14 3 has a corresponding design and features a planet carrier 16, a ring gear 20, a sun gear 22, and several planet gears 18 that rotate around the planet carrier 16 and mesh alternately with the ring gear 20 and the sun gear 22 in a helical gear mesh. A feature of the design of the planetary gear 10 is that each of the sun gears 22 is connected to the planet carrier 16 of the subsequent planetary stage 14 in a rotationally fixed and axially displaceable manner. Another feature of the design is that the planet carriers 16 2 and 16 3 of the second and third planetary stages 14 2 and 14 3 are each mounted on housing-side support flanges 26 via bearings 24.Three support flanges 26 1 to 26 3 are provided, the first two of which are each located between the planetary stages 14 1 to 14 3, and one of which is located on the output side of the third planetary stage 14 3. The axial force of the second planetary stage 14 2 is supported via the first support flange 26 1 and the bearing 24, and the axial force of the third planetary stage 14 3 is supported via the second support flange 26 2 and the radially inner bearing 24 during reversing operation. The axial force of the second planetary stage 14 2 is supported via the second support flange 26 2 and the radially outer bearing 24, and the axial force of the third planetary stage 14 3 is supported via the third support flange 26 3 and the bearing 24 during nominal operation.

[0027] The Figure 3Figure 1 shows a section of a planetary gear set 10 in a possible embodiment with a rotating-in-rotating bearing of the sun gear 22 relative to the planet carrier 16 1 in the first planetary stage 14 1. The sun gear 22 is rotatably and axially supported on an axially oriented bearing flange 28 of the planet carrier 16 1 via a rolling bearing 30. It can be seen that the bearing flange 28 is a separate annular component and is connected to the planet carrier 16 1 in a suitable manner, for example, by several circumferentially distributed and axially extending screw connections. Alternatively, the bearing flange 28 can also be formed integrally with the planet carrier 16 1, which is not shown here.

[0028] The planet carrier 16 2 of the second planetary stage 14 2 is also rotatably and load-bearing mounted relative to the planet carrier 16 1 of the first planetary stage 14 1 via the rolling bearing 30, specifically indirectly via the sun gear 22 of the first planetary stage 14 1. For this purpose, the sun gear 22 of the first planetary stage 14 1 has an axial width that extends beyond the toothed area common to the planet gear 18, so that the sun gear 22 can also be referred to as a sun shaft. The sun gear 22 of the first planetary stage 14 1 is held rotationally fixed on the inside circumference of a hub 32 of the second planet carrier 16 2 by means of a toothed pair. The sun gear 22 of the first planetary stage 14 1 can be fixed axially relative to the hub 32 in a suitable manner, for example by means of a screw connection, which is not shown here.

[0029] The Figure 4Figure 1 shows a section of a planetary gear set 10 in another possible embodiment with a rotating-in-rotating bearing of the sun gear 22 relative to the planet carrier 16 1 in the first planetary stage 14 1. The arrangement of the rolling bearing 30 is such that it is located in an axial area 34 formed by an axially overlapping arrangement of the bearing flange 28 of the planet carrier 16 1 of the first planetary stage 14 1 with the hub 32 of the planet carrier 16 1 of the second planetary stage 14 2. For this purpose, the bearing flange 28 of the planet carrier 16 1 of the first planetary stage 14 1 has been extended in the axial direction. The hub 32 of the planet carrier 16 2 of the second planet stage 14 2 projects in the opposite axial direction into the first planet stage 14 1 and forms the overlapping axial area 34 with the extended bearing flange 28.

[0030] The Figure 5Figure 1 shows a section of a planetary gear set 10 in another possible embodiment with a rotating-in-rotating bearing of the sun gear 22 relative to the planet carrier 16 1 in the first planetary stage 14 1. A second rolling bearing 36 is provided, by means of which the second planet carrier 16 1 is rotatably mounted relative to the gear housing 12 on the side facing away from the first planetary stage 14 1. Reference numeral 38 denotes a shaft-hub connection, which comprises an expanding element seated within the sun gear 22 for acting the sun gear 22 radially outwards against the second planet carrier 16 2. The expanding element can be of multi-part construction and include a ring core and a wedge ring seated between the ring core and the sun gear 22 and acted upon in the axial direction.

[0031] Based on the Figure 6and their illustrations a), b) and c) explain, using the first planetary stage 14 1 as an example, how the axial force F generated via the helical gearing acts. First, illustration a) shows the relationships that the Figure 2The described design of the planetary gear 10 corresponds to this. Due to the helical gearing, axial forces FP1 and FP2 are generated at the planet gears 18 and the planet carrier 161, which act in opposite directions, so that FP1 - FP2 = 0. The planet carrier 161 is therefore free of forces. The axial force FH generated at the ring gear 20 is absorbed and supported by the housing 12. The axial force FS generated at the sun gear 22 acts in the opposite direction to the axial force FH and is absorbed by the planet carrier 162 and, as described above, supported by a support flange 26 with bearing 24. The support flange and bearing are not shown here for the sake of clarity. The axial force Fs generated at the sun gear 22 is transferred via the second planetary stage 14 2 and the support flange 26 into the housing 12, resulting in the requirements for installation space and component strength already described above.

[0032] The figures in b) and c) of the Figure 6 The ratios shown correspond to those of the Figure 3 and 4 described embodiment of the planetary gear 10, with the crucial difference that between illustrations b) and c) the Figure 6The helix direction of the helical gears in the planetary gear stage 16 is reversed. Illustration b) assumes a conventional right-hand or left-hand helix direction, while illustration c) assumes a reversed left-hand or right-hand helix direction. Due to the reversed helix direction, the individual axial forces acting on the respective gear element are opposite in illustrations b) and c). Furthermore, due to the rotating-in-rotating bearing of the sun gear 22 on the planet carrier 16, the axial force FS arising on the sun gear 22 is transferred to the planet carrier 16 via the rolling bearing 30. Since the axial force FP2 of the planet gear 18 is also transferred to the planet carrier 16, FS - FP2 = 0, meaning this subsystem is force-free. Additionally, the axial force FR of the ring gear 20 is absorbed and supported by the housing 12.Consequently, the planet carrier 16 is not free from force due to the axial force FP1 of the planet gear 18, and this axial force FP1 is supported via the main bearing unit 108, as described above. The difference between the conditions shown in b) and c) is that the main bearing unit 108 is subjected to the axial force FP1 in opposite directions. In the conditions shown in c), the axial force FP1 counteracts the wind forces of the rotor 106 acting on the main bearing unit 108, thus relieving the load on the main bearing unit. Reference symbol list

[0033] 10 Planetary gear 12 Gearbox housing 14 Planetary stage 16 Planetary carrier 18 Planetary gears 20 Ring gear 22 Sun gear 24 Rolling bearing 26 Support flange 28 Bearing flange 30 Rolling bearing 32 Hub 34 Axial area 36 Rolling bearing 38 Shaft-hub connection 100 Wind turbine 102 Drive train 104 Rotor flange 106 Multi-blade rotor 108 Main bearing unit 112 Generator 114 Machine carrier 116 Tower 118 Main shaft 120 Bearing housing 124 Generator shaft 126 Flange

Claims

1. Planetary transmission (10) for a wind turbine (100) driven by a rotor (106), having at least one first planetary stage (141), which is arranged about an axis of rotation (AD) in a transmission housing (12), and at least one second planetary stage (142), wherein the first planetary stage (141) has a planet carrier (161) and a ring gear (20), and the planet carrier (161) is suitable for an at least indirect drive connection to the rotor (72), and wherein the planet carrier (161) has a plurality of planet gears (18) which revolve with the planet carrier (161) and alternately mesh with the ring gear (20) and a sun gear (22), wherein the sun gear (22) is mounted in relation to the planet carrier (161) of the first planetary stage (14) so as to be rotatable about the axis of rotation (AD) and axially supported via a bearing assembly (30), and a planet carrier (162) of the second planetary stage (142) is mounted in relation to the planet carrier (161) of the first planetary stage (141) so as to be rotatable via the bearing assembly (30), which is realized as a rolling bearing assembly, characterized in that the bearing assembly (30) is arranged within the sun gear (22).

2. Planetary transmission (10) according to Claim 1, characterized in that the meshing engagement is helically toothed, the toothing having a right-hand or left-hand direction of the helix.

3. Planetary transmission (10) according to Claim 1 or 2, characterized in that the sun gear (22) is mounted at least indirectly on an axially directed bearing flange (28) of the planet carrier (16).

4. Planetary transmission (10) according to Claim 3, characterized in that the bearing flange (28) is formed integrally with the planet carrier (16) or, as an annular component connected to the planet carrier (16), forms a functional unit.

5. Planetary transmission (10) according to any one of Claims 1 to 4, characterized in that the planet carrier (162) of the second planetary stage (142) is connected to the sun gear (22) of the first planetary stage (141) for conjoint rotation and so as to be axially supported.

6. Planetary transmission (10) according to any one of Claims 1 to 5, characterized in that the rolling bearing assembly (30) is arranged in an axial region (34) formed by an axially overlapping arrangement of the bearing flange (28) of the first planet carrier (161) with a hub (32) of the second planet carrier (162).

7. Planetary transmission (10) according to Claim 6, characterized in that the sun gear (22) of the first planetary stage (161) is held circumferentially on the hub (32) of the second planet carrier (162) via a pair of toothings for conjoint rotation.

8. Planetary transmission (10) according to Claim 7, characterized in that the sun gear (22) of the first planetary stage (161) is screwed in the axial direction in relation to the second planet carrier (162).

9. Planetary transmission (10) according to any one of Claims 1 to 8, characterized in that a second bearing assembly (36) is provided, via which the second planet carrier (162) is rotatably mounted in relation to the transmission housing (12) on the side facing away from the first planetary stage (161).

10. Planetary transmission (10) according to any one of Claims 1 to 9, characterized in that the second planet carrier (162) has a support on one side.

11. Powertrain (102) for a wind turbine (100) for the torque-transmitting connection of a rotor (106) to a generator (112), comprising a main bearing unit (108) having a bearing housing (120) and a main shaft (118), and a transmission (10) driven by the main shaft (118), wherein the transmission (10) drives the generator (112) at least indirectly, characterized in that the transmission (10) is designed as a planetary transmission according to any one of the preceding claims.

12. Wind turbine (100), comprising a rotor flange (104) with a rotor (106) and a generator (112), wherein a powertrain (102) which is held on a machine support (114) and connects the rotor flange (104) to the generator (112) is provided, characterized in that the powertrain (102) is designed according to Claim 11.