WO2008074320A1

WO2008074320A1 - A gear system for a yaw drive or a pitch drive for a wind turbine

Info

Publication number: WO2008074320A1
Application number: PCT/DK2006/000721
Authority: WO
Inventors: Thomas Krag Nielsen
Original assignee: Vestas Wind Systems A/S
Priority date: 2006-12-18
Filing date: 2006-12-18
Publication date: 2008-06-26

Abstract

A gear system for use in a wind turbine, in particular for a yawing system or for a pitching system. The gear system comprises a drive unit comprising a drive motor (3), a primary pinion (4) connected to an being driven directly by the drive unit and an output gear part, e.g. in the form of a toothed gear ring (2). The gear system further comprises at least one secondary pinion (5) positioned in torque transmitting engagement with the primary pinion (6) and the output gear (2) part. The secondary pinion is positioned in such a manner that the direction of torque transmission between the primary pinion and the secondary pinion and the direction of torque transmission between the secondary pinion and the output gear part are substantially perpendicular to each other.

Description

A GEAR SYSTEM FOR A YAW DRIVE OR A PITCH DRIVE FOR A WIND TURBINE

FIELD OF THE INVENTION

The present invention relates to a gear system for use in a wind turbine. The gear system of the present invention is particularly suitable for use in a yaw drive or a pitch drive of a wind turbine.

BACKGROUND OF THE INVENTION

Yawing systems and pitching systems of wind turbines are normally provided with one or more drive units, each comprising a drive motor, possibly a geared motor, and a pinion which transfers torque directly from the drive motor to an output gear part, e.g. in the form of a toothed gear ring, and preferably by means of intermeshing teeth. In such an arrangement only a few teeth of the pinion and the output gear part will mesh at any given time. Possibly, only a single tooth from each part may mesh at any given time. Thus, the torque is transmitted via a single or only a few teeth, thereby causing considerable wear on the teeth. Furthermore, the linear contact between the meshing teeth is not optimal. This even further increases problems relating to wear on the teeth. Finally, the load on the pinion transferring the torque is relatively high, and it is therefore necessary to use strong materials, in terms wear as well as load. This adds to the manufacturing costs of the gear system.

SUMMARY OF THE INVENTION

It is, thus, an object of the invention to provide a gear system for a yawing system or a pitching system for a wind turbine, in which the wear on the parts of the gear system is reduced as compared to similar prior art gear systems.

It is a further object of the invention to provide a gear system for a yawing system or a pitching system for a wind turbine, in which the load applied to the parts of the gear system is reduced as compared to similar prior art gear systems.

According to a first aspect of the invention the above and other objects are fulfilled by providing a gear system for use in a wind turbine, the gear system comprising:

- a drive unit for driving the gear system, said drive unit comprising a drive motor,

- a primary pinion connected to and being directly driven by the drive unit, - an output gear part adapted to output a torque from the gear system, and

- at least one secondary pinion positioned in torque transmitting engagement with the primary pinion and in torque transmitting engagement with the output gear part, the secondary pinion(s) thereby being adapted to transfer torque from the primary pinion to the output gear part,

wherein the secondary pinion(s) is/are positioned in such a manner that the direction of torque transmission between the primary pinion and the secondary pinion is at least substantially perpendicular to the direction of torque transmission between the secondary pinion(s) and the output gear part.

The drive unit comprises a drive motor. The drive motor is preferably a geared motor, but it may alternatively be another kind of motor. The drive unit drives the gear system, i.e. the drive unit provides the necessary torque for driving the gear system, and this is obtained by means of the motor.

The primary pinion is connected to the drive unit, and it is directly driven by the drive unit. In the present context the term 'directly driven' should be interpreted to mean that the drive unit transfers torque to the primary pinion without an intermediate part, such as an intermediate pinion or gear wheel. Thus, the drive unit and the primary pinion in combination corresponds to and resembles a prior art drive unit as described above.

The output gear part is adapted to output a torque from the gear system. Accordingly, when the output gear part is rotated relatively to other parts of the gear system, a torque is outputted from the gear system. It should be noted that the output gear part is not necessarily rotated relatively to the surroundings. For instance, in the case that the gear system is a yawing system, the output gear part may advantageously be a gear ring which is mounted on the tower of the wind turbine, while a number of drive units are connected to and rotates along with the nacelle during yawing. However, torque is outputted from the gear system due to a relative rotational movement between the output gear part and one or more other parts of the gear system.

At least one secondary pinion is positioned in torque transmitting engagement with the primary pinion as well as with the output gear part. Thus, each secondary pinion forms a torque path between the primary pinion and the output gear part. Thus, during normal operation of the gear system the drive unit drives the primary pinion. As a consequence, the primary pinion transfers torque to the secondary pinion(s), and the secondary pinion(s) accordingly transfer(s) torque to the output gear part. It is an advantage to transfer torque between the drive unit and the output gear part via at least one secondary pinion, because it is thereby possible to adjust the gear system to obtain an improved linear contact between the mating teeth.

The secondary pinion(s) is/are positioned in such a manner that the direction of torque transmission between the primary pinion and each secondary pinion is at least substantially perpendicular to the direction of torque transmission between the secondary pinion(s) and the output gear part. In the present context the term ^λat least substantially perpendicular' should be interpreted to mean that the angle between the two directions is at least 70°, such as at least 75°, such as at least 80°, such as at least 85°, such as at least 88°. This allows each secondary pinion to adjust its position with respect to the primary pinion, as well as with respect to the output gear part in such a manner that an optimal linear contact is obtained in both of these torque transmission. Accordingly, this arrangement allows the secondary pinion(s) to adjust to a position between the primary pinion and the output gear part which permits an improved linear contact, in particular between the teeth of the secondary pinion(s) and the teeth of the output gear part, but also between the teeth of the primary pinion and the teeth of the secondary pinion(s). This is an advantage because an improved linear contact improves the torque transfer and reduces wear on the engaging teeth.

The gear system may advantageously be or form part of a yawing system for a wind turbine, or of a pitching system for a wind turbine.

The gear system may comprise at least two secondary pinions. According to this embodiment the primary pinion drives at least two secondary pinions, each transferring torque to the output gear part. Thereby, torque is transferred from the drive unit to the output gear part via at least two torque paths, i.e. via the secondary pinions. Accordingly, the load is shared between the torque paths, and thereby between the secondary pinions. Accordingly, the load on each of the secondary pinions is reduced as compared to the situation where only one pinion, either one secondary pinion or the primary pinion directly transferring torque to the output gear part. Thereby the wear on the secondary pinions is reduced, and it is possible to choose a material for the secondary pinions which is less durable. Thus, other factors may be taken into consideration when choosing material, e.g. price, weight, etc. Accordingly, these factors may be improved, i.e. the manufacturing costs may be lowered if a cheaper material is used, or the total weight of the gear system may be reduced if a lighter material is used. Preferably, the primary pinion drives exactly two secondary pinions.

The load sharing may be very accurate, since it is limited to the ratio of transmitted torque and internal friction. When applying torque to the primary pinion, the primary pinion will start rotating within the backlash of the gearing. Assuming that the backlash in one torque path is much smaller than the backlash in the other torque path, the primary pinion will start to rotate with the first path as centre. Now the primary pinion will move until the backlash in the other path is eliminated. The two torque paths have thereby created a torque balance, and the primary pinion will now rotate with respect to its own symmetry axis.

In one situation, one of the secondary pinions may have an oval shape. This will cause the backlash to vary during operation. The system will in this case equalize the varying backlash and torsion, since the primary pinion will Yloat' to a suitable position.

The primary pinion may be allowed to move in a rotational plane defined by the primary pinion. This may, e.g., be obtained by means of a cardanic function, e.g. by means of a cardanic coupling. This allows the primary pinion to adjust to the secondary pinions in order to obtain an optimal relative position, and in order to obtain torsion balance between the primary pinion and the secondary pinions. Thereby it can be ensured that the load sharing between secondary pinions is kept substantially equal, even if grinding variations between the pinions occur. Furthermore, the primary pinion is preferably allowed to tilt in any direction, e.g. by means of a cardanic function.

According to one embodiment, the primary pinion has a first diameter and each of the secondary pinion(s) has a second diameter, said first diameter being smaller than said second diameter. Thereby it can be ensured that the secondary pinion(s) contact the output gear part while the primary pinion does not.

The output gear part may be or comprise a gear ring, e.g. an internally toothed gear ring or an externally toothed gear ring. In the case that the gear ring is internally toothed, it is possible to accommodate the pinions within a perimeter defined by the gear ring, and thereby a relatively compact design is obtained.

Each of the secondary pinion(s) may comprise a spherical bearing. Such a spherical bearing in principle allows a pinion mounted on the bearing to tilt in any direction. Thereby each of the secondary pinion(s) is allowed to adjust in such a manner that optimal meshing is obtained between the secondary pinion(s) and the primary pinion, as well as between the secondary pinion(s) and the output gear part. The spherical bearing may, e.g., be a roller bearing or a plain bearing, or any other suitable kind of bearing.

Each of the secondary pinion(s) may be mounted on an eccentric axle. This allows the backlash and the play between the pinions to be fine tuned in a mounting stage by rotating the axle to a certain position in which the backlash is optimal. The drive motor may be electrically driven or hydraulically driven, or the drive motor may be any other suitable kind of motor.

The gear system may further comprise

- at least one additional drive unit for driving the gear system, said additional drive unit(s) comprising a drive motor,

- at least one additional primary pinion connected to and being directly driven by an additional drive unit, and

- at least one additional secondary pinion positioned in torque transmitting engagement with an additional primary pinion and in torque transmitting engagement with the output gear part, the additional secondary pinion(s) thereby being adapted to transfer torque from the additional primary pinion to the output gear part.

According to this embodiment the gear system comprises two or more substantially identical drive units, each being connected to primary pinions and secondary pinions as described above. The drive units cooperate in driving the gear system, and they may advantageously be arranged substantially equidistantly along the output gear part.

According to a second aspect of the invention the above and other objects are fulfilled by providing a gear system for use in a wind turbine, the gear system comprising:

- a primary pinion connected to and being directly driven by the drive unit,

- a output gear part adapted to output a torque from the gear system, and

- at least two secondary pinions positioned in torque transmitting engagement with the primary pinion and in torque transmitting engagement with the output gear part, the secondary pinions thereby each being adapted to transfer torque from the primary pinion to the output gear part in a load sharing manner.

It should be noted that a skilled person would readily recognise that any feature described in combination with the first aspect of the invention may equally be combined with the second aspect of the invention, and vice versa. According to the second aspect of the invention, the gear system comprises at least two secondary pinions. As described above, at least two torque paths are thereby obtained, and the load may thereby be shared between these torque paths. The advantages described above are thereby obtained. Preferably, the gear system comprises exactly two secondary pinions, and exactly two torque paths are thereby obtained.

The load is preferably shared substantially equally between the pinions. Thus, one of the secondary pinions may carry between 30% and 50% of the torque transferred from the primary pinion to the secondary pinions and/or one of the secondary pinions may carry between 50% and 70% of the torque transferred from the primary pinion to the secondary pinions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail with reference to the accompanying drawings in which

Fig. 1 is a perspective view of a part of a yawing system comprising a gear system according to an embodiment of the invention,

Fig. 2 is a cross sectional view of the yawing system of Fig. 1, and

Fig. 3 is a schematic illustration of a gear system according to an embodiment of the invention, and illustrating torque transmission in the gear system.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a part of a yawing system 1. The yawing system 1 comprises an internally toothed gear ring 2 and a drive unit 3 comprising a motor (not visible). The drive unit 3 is connected to a primary pinion 4 in meshing engagement with two secondary pinions 5. The secondary pinions 5 both mesh with the toothing of the gear ring 2. The primary pinion 4 and the secondary pinions 5 are arranged relatively to each other in such a way that their rotational axes define a substantially straight line. This ensures that the direction of torque transmission from the primary pinion 4 to each of the secondary pinions 5 is substantially perpendicular to the direction of torque transmission from the secondary pinions 5 to the gear ring 2. This will be explained further below with reference to Fig. 3. The yawing system 1 shown in Fig. 1 is preferably operated in the following manner. When it is desired to operate the yawing system 1, the drive unit 3 is operated, thereby causing the primary pinion 4 to rotate. Due to the meshing engagement between the primary pinion 4 and the secondary pinions 5, the secondary pinions 5 are thereby also caused to rotate. Due to the meshing engagement between the secondary pinions 5 and the gear ring 2 this results in a relative rotational movement between the pinions 4, 5 on the one hand and the gear ring 2 on the other hand. Since the gear ring 2 is normally mounted on a tower and the pinions 4, 5 are normally mounted on a nacelle, this will result in a relative rotational movement between the tower and the nacelle, i.e. yawing is obtained.

The fact that the yawing system 1 comprises two secondary pinions 5 ensures that the load is shared between the two torque paths defined by the two secondary pinions 5. Accordingly, the wear on each of the secondary pinions 5 is reduced as compared to the situation where a single pinion must transfer the entire torque from the drive unit 3 to the gear ring 2. This has already been described in detail above.

Fig. 2 is a cross sectional view of the yawing system 1 of Fig. 1 through the drive unit 3 and the primary pinion 4. In Fig. 2 it is possible to see that the drive motor 6 drives the primary pinion 4 via a gear coupling shaft 7.

It should be noted that even though Figs. 1 and 2 show a yawing system and the above description therefore refers specifically to a yawing system, the gear system shown in Figs. 1 and 2 and the description above would equally apply to a pitching system for a wind turbine, i.e. a gear system which is used for pitching the blades of a wind turbine.

Fig. 3 is a schematic illustration of a gear system according to an embodiment of the invention. Fig. 3 illustrates torque transmission in the gear system. Fig. 3 shows a gear ring 2, a primary pinion 4 and two secondary pinions 5a, 5b. The primary pinion 4 is able to rotate about a rotational axis 8, and each of the secondary pinions 5a, 5b is able to rotate about a respective rotational axes 9a, 9b. The pinions 4, 5 are arranged in such a manner that the three rotational axes 8, 9 define a substantially straight line. Furthermore, the primary pinion 4 has a diameter which is smaller than the diameter of the secondary pinions 5, and it is clear from Fig. 3 that this has the effect that the secondary pinions 5 are able to engage the gear ring 2 while the primary pinion 4 is not.

When the primary pinion 4 is rotated about rotational axis 8 as described above, torque is transferred from the primary pinion 4 to each of the secondary pinions 5a, 5b, along a direction indicated by lines 10a, 10b, respectively. This will cause the secondary pinions 5a, 5b to rotate about rotational axes 9a, 9b, respectively, and torque is transferred from the secondary pinions 5a, 5b to the gear ring 2. This torque transfer takes place along directions indicated by lines 11a, lib, respectively. Since the radius of curvature of the ring gear 2 is relatively large as compared the dimensions of the pinions 4, 5, the angles A, B between lines 10 and 11 are approximately 90°. This allows the pinions 4, 5 to adjust relatively to each other and relatively to the gear ring 2 in such a manner that an optimal linear contact can be achieved between the teeth of the secondary pinions 5 and the teeth of the ring gear 2, respectively between the teeth of the primary pinion 4 and the teeth of the secondary pinions 5. As described above, this is a great advantage.

The function of optimizing linear contact may be divided into two functions, i.e. linear contact of the output gear part/ring gear 2 and the secondary pinions 5, and linear contact of the primary pinion 4 and the secondary pinions 5.

Regarding the linear contact of the ring gear 2 and the secondary pinions 5, when the system adjusts the linear contact of the ring gear 2 and the secondary pinions 5, the secondary pinions 5a, 5b will tilt over the respective axis 11a, lib in such a manner that contact along the entire gearing (tooth flange) is ensured. This will not disturb the linear contact of the primary pinion 4 and the secondary pinions 5, due to the angles A, B being approximately 90°, but will only cause slight axial movement in the gearing.

Regarding the linear contact of the primary pinion 4 and the secondary pinions 5, the primary pinion 4, being capable of tilting in all directions, will optimize the linear contact of both of the secondary pinions 5. During this, both of the secondary pinions 5 will tilt differently over the common axis 10. This will cause axial movement in the gearing of the ring gear 2 and the secondary pinions 5. This axial movement has no impact on the linear contact. Thus, the two different axial movements are very small and might appear independently due to the angles A, B being approximately 90°.

Claims

1. A gear system for use in a wind turbine, the gear system comprising:

- a primary pinion connected to and being directly driven by the drive unit,

- an output gear part adapted to output a torque from the gear system, and

wherein the secondary pinion(s) is/are positioned in such a manner that the direction of torque transmission between the primary pinion and each secondary pinion is at least substantially perpendicular to the direction of torque transmission between the secondary pinion(s) and the output gear part.

2. A gear system according to claim 1, wherein the gear system is or forms part of a yawing system for a wind turbine.

3. A gear system according to claim 1, wherein the gear system is or forms part of a pitching system for a wind turbine.

4. A gear system according to any of the preceding claims, wherein the gear system comprises at least two secondary pinions.

5. A gear system according to claim 4, wherein the primary pinion is allowed to move in a rotational plane defined by the primary pinion.

6. A gear system according to claim 5, wherein the movability of the primary pinion is obtained by means of a cardanic function.

7. A gear system according to any of the preceding claims, wherein the primary pinion has a first diameter and each of the secondary pinion(s) has a second diameter, said first diameter being smaller than said second diameter.

8. A gear system according to any of the preceding claims, wherein the output gear part is or comprises a gear ring.

9. A gear system according to claim 8, wherein the gear ring is internally toothed.

10. A gear system according to any of the preceding claims, wherein each of the secondary pinion(s) comprises a spherical bearing.

11. A gear system according to any of the preceding claims, wherein each of the secondary pinion(s) is mounted on an eccentric axle.

12. A gear system according to any of the preceding claims, wherein the drive motor is electrically driven.

13. A gear system according to any of claims 1-11, wherein the drive motor is hydraulically driven.

14. A gear system according to any of the preceding claims, further comprising

15. A gear system for use in a wind turbine, the gear system comprising:

- a primary pinion connected to and being directly driven by the drive unit,

- a output gear part adapted to output a torque from the gear system, and - at least two secondary pinions positioned in torque transmitting engagement with the primary pinion and in torque transmitting engagement with the output gear part, the secondary pinions thereby each being adapted to transfer torque from the primary pinion to the output gear part in a load sharing manner.

16. A gear system according to claim 15, wherein one of the secondary pinions carries between 30% and 50% of the torque transferred from the primary pinion to the secondary pinions.

17. A gear system according to claim 15 or 16, wherein one of the secondary pinions carries between 50% and 70% of the torque transferred from the primary pinion to the secondary pinions.