Flexible sun wheel

Abstract

Sun gear (3) for a planetary gear (1) with an external toothing (4) and an inner circumference (10), in the area of ​​which the sun gear (3) is rotationally fixedly coupled to a central, flexible shaft (2), wherein the shaft (2) has an outer circumference (8), wherein a bending element (9) is arranged between the external toothing (4) of the sun gear (3) and the outer circumference (8) of the shaft (2), wherein the bending element (9) is designed to be flexible in such a way that the external toothing (4) is tiltable at least in certain areas relative to the longitudinal axis of the shaft (2), characterized in that the bending element (9) and the shaft (2) are connected to each other by force and / or material bonding.

Description

[0001] The present invention relates to a sun gear and a planetary gear according to the type defined in more detail in the preamble of claims 1 and 12.

[0002] Particularly in wind turbines, three or more planetary gears are typically used to ensure even distribution in a planetary gear. This allows the number of meshing teeth to be increased, distributing the load across a large number of individual components. Advantageously, the individual components can be made smaller and lighter. However, if the planetary gear has three or more planetary gears, the load may be distributed unevenly among the individual planetary gears, particularly due to manufacturing tolerances.

[0003] To balance the load between the planetary gears, a flexible sun gear is known, for example, from EP 1 717 489 A2. This is coupled to a shaft at one end. The other end is unsupported. The sun gear meshes with the surrounding planetary gears. If a planetary gear is radially overloaded, the central sun gear bends slightly, distributing the load among the remaining planetary gears.

[0004] The problem underlying the invention is solved by the features of patent claims 1 and 12. Further advantageous embodiments emerge from the subclaims and the drawing.

[0005] A sun gear for a planetary gear train is proposed, having external teeth and an inner circumference in which the sun gear is rotationally fixedly coupled to a central, flexible shaft. The shaft has an outer circumference. A flexural element is arranged between the external teeth of the sun gear and the outer circumference of the shaft. The flexural element is designed to be flexible such that the external teeth can be tilted, at least in some areas, relative to the longitudinal axis of the shaft. A major problem with previously known sun gears that are adjustable for load balancing is that the sun gear teeth tilt relative to the planetary gear teeth when the shaft is bent. This inclination leads to poor load distribution across the planetary gear train, thus reducing efficiency. Furthermore, uneven meshing between the sun gear and planet gears causes uneven wear of the tooth flanks.However, due to the additional bending element arranged between the external teeth of the sun gear and the outer circumference of the shaft, the external teeth of the sun gear in this case can also tilt relative to the shaft. To compensate for the load, the flexible shaft initially bends, resulting in an even load distribution between the individual planet gears. In addition, the bending element tilts the sun gear relative to the shaft in such a way that the external teeth remain essentially parallel to the longitudinal axis of the unbent shaft. Advantageously, the external teeth therefore do not tilt relative to the engaging planet gears, ensuring a homogeneous meshing of the tooth flanks of the sun gear with those of the planet gears and thus an optimal load distribution across the tooth flanks.

[0006] In the context of this document, a central flexible shaft is also understood to mean a shaft whose shaft is essentially rigid, but which is pivotally mounted at its end remote from the sun gear in such a way that the end of the central shaft near the sun gear has a certain mobility in the radial direction.

[0007] It is advantageous if the flexure is designed as a ring. This allows the sun gear to tilt relative to the shaft not just in certain areas, but across the entire circumference of the shaft.

[0008] If the bending element is formed as one piece with the sun gear and / or the shaft, the manufacturing costs can advantageously be reduced.

[0009] A simple and cost-effective production of the flexural element can be achieved if the flexural element is designed as a cross-sectional taper of the sun gear. This allows the sun gear and the flexural element to be made of the same material. The cross-sectional taper allows the elasticity or flexibility of the sun gear in the area of ​​the flexural element to be designed in such a way that the external gearing can be tilted accordingly relative to the shaft.

[0010] It is advantageous if the cross-section of the sun gear and / or the flexure tapers radially inward in the longitudinal direction of the shaft. This does not reduce the strength of the sun gear in the area of ​​its external teeth, but simply increases the flexibility in the area of ​​the flexure. The result is therefore solely the desired tilting of the external teeth relative to the shaft. Undesirable deformation of the external teeth, however, is avoided.

[0011] To allow only tilting of the sun gear relative to the shaft, but not deformation of the external gearing, it is further advantageous if the sun gear, together with the bending element, has a substantially T-shaped and / or double-T-shaped cross-section. The bending occurs essentially in the vertical beam of the T.

[0012] To ensure a secure connection of the sun gear and / or flexural element to the shaft, it is advantageous if the sun gear and / or flexural element, which is designed with a T-shaped and / or double-T-shaped cross-section, has a base to which the sun gear and / or flexural element are connected to the shaft in a rotationally fixed manner. To prevent the sun gear from becoming detached from the shaft, it is advantageous if the sun gear, the flexural element, and / or the shaft are connected to one another in a force-fitting, form-fitting, and / or material-fitting manner.

[0013] In order to be able to optimally adapt the bending properties of the flexible shaft to the corresponding load conditions, it is advantageous if the shaft is designed as a hollow and / or solid shaft.

[0014] It is advantageous if the shaft has a free, unsupported end so that it can adapt to load compensation in this area.

[0015] In order to increase the flexibility of the shaft and at the same time ensure a uniform engagement of the tooth flanks of the sun gear with those of the planet gears, it is advantageous if the sun gear is arranged on the shaft in the area of ​​the free end.

[0016] A planetary gear set comprising a central sun gear, a surrounding ring gear, and at least two planet gears arranged between these two is also proposed. The planet gears are held by the planet carrier. The sun gear is designed according to one or more of the preceding embodiments. This advantageously ensures both load balancing through a bending of the flexible shaft and parallel meshing of the sun gear with the planet gears.

[0017] To ensure the sun gear can optimally adapt to the differently loaded planetary gears, it is advantageous for the sun gear and the planetary gears to have radial play when unloaded. This also ensures optimal tilting of the external gearing relative to the shaft.

[0018] The invention is explained in more detail below with reference to a drawing. It shows: Fig. 1 a cross-section through a sun gear coupled to a central, flexible shaft in a rotationally fixed manner.

[0019] Fig. Figure 1 shows a cross-sectional view of a planetary gear 1 with a central, flexible shaft 2 and a sun gear 3. The sun gear 3 has external teeth 4, which mesh with planetary gears (not shown here). These planetary gears are rotatably supported by a planet carrier and mesh with a ring gear (also not shown here) in the radially outer region of the planetary gear 1.

[0020] In particular, manufacturing tolerances can lead to an uneven load distribution between the individual planetary gears. To enable load balancing between them, the central shaft 2 is designed to be flexible. Shaft 2 firstly has a bearing section 5 in which it is rotatably mounted in the planetary gear 1. Furthermore, the flexible shaft 2, which in the present embodiment is designed as a hollow shaft, has a free, unsupported end 6. In the area between the bearing section 5 and the free end 6, the shaft 2 has a flexible section 7. This has a smaller outer diameter, at least compared to the bearing section 5.

[0021] The sun gear 3 is rotationally fixedly coupled to the shaft 2 in the region of the free end 6. To enable tilting of the external toothing 4 relative to the longitudinal axis A of the shaft 2, a bending element 9 is arranged between the external toothing 4 of the sun gear 3 and the outer circumference 8 of the shaft 2.

[0022] The bending element 9 is designed as a ring and extends over the entire outer circumference 8 of the flexible shaft 2. The bending element 9 is formed integrally with the inner circumference 10 of the sun gear 3. Of course, a multi-part design of the sun gear 3 and the bending element 9 would also be possible.

[0023] The bending element 9 has a smaller width along the longitudinal axis A than the sun gear 3 in the region of its external toothing 4. Consequently, the bending element 9 is designed as a cross-sectional taper of the sun gear 3. To ensure that the external toothing 4 of the sun gear 3 cannot tilt relative to the outer circumference 8 of the flexible shaft 2, the sun gear 3, together with the one-piece bending element 9, has a T-shaped cross-section.

[0024] In the lower area of ​​the T-shaped cross-section, the bending element 9 has a base 11. For the rotationally fixed coupling of the sun gear 3 with the shaft 2, the bending element 9, which is formed in one piece with the sun gear 3, is connected in the area of ​​its base 11 to the flexible shaft 2, in the area of ​​its free end 6, in a form-fitting, force-fitting and / or material-fitting manner. Thus, when the planetary gears are subjected to different loads, the flexible shaft 2 can bend around its bearing section 5 due to its flexible section 7. In this case, the free end 6 of the shaft 2 is essentially bent from its Fig.1. Without the flexure 9, the sun gear 3, which is connected to the free end 6 of the shaft 2, would also follow this movement. This would cause the external toothing 4 to tilt relative to the planet gears (not shown here). The result would be an uneven load distribution across the width of the meshing tooth flanks of the sun gear 3 and the radially surrounding planet gears.

[0025] In order to compensate for such an inclination of the external toothing 4 relative to the planetary gears (not shown here), the sun gear 3 has the bending element 9. Thus, the sun gear 3 can tilt in the region of its external toothing 4 relative to the outer circumference 8 of the flexible shaft essentially in the opposite direction such that a parallel position of the external toothing 4 to the longitudinal axis A of the shaft 2 is ensured in the rest state. The external toothing 9 is thus designed to be tiltable about the base 11. As a result, the tooth flanks of the external toothing 4 of the sun gear 3 engage evenly with the tooth flanks of the surrounding planetary gears without canting. Due to the thus optimized load distribution across the width, the efficiency of the planetary gear 1 is increased.

[0026] The present invention is not limited to the illustrated and described embodiment. Modifications within the scope of the patent claims are possible, as are combinations of features, even if they are illustrated and described in different embodiments. Reference symbol 1 planetary gear 2nd wave 3 sun gear 4 External gearing 5 storage section 6 Free end 7 Flexible section 8 Outer circumference 9 Bending element 10 inner circumference 11 Base A Longitudinal axis

Claims

[1] Sun gear (3) for a planetary gear (1) with an external toothing (4) and an inner circumference (10), in the area of ​​which the sun gear (3) is coupled in a rotationally fixed manner to a central, flexible shaft (2), wherein the shaft (2) has an outer circumference (8), wherein a bending element (9) is arranged between the external toothing (4) of the sun gear (3) and the outer circumference (8) of the shaft (2), wherein the bending element (9) is designed to be flexible in such a way that the external toothing (4) can be tilted at least in some areas relative to the longitudinal axis of the shaft (2), characterized by that the bending element (9) and the shaft (2) are connected to one another in a force-fitting and / or material-fitting manner. [2] Sun gear according to the previous claim, characterized by that the bending element (9) is designed as a ring. [3] Sun gear according to one or more of the preceding claims, characterized by that the bending element (9) is formed in one piece with the sun gear (3) and / or the shaft (2). [4] Sun gear according to one or more of the preceding claims, characterized by that the bending element (9) is designed as a cross-sectional taper of the sun gear (3). [5] Sun gear according to one or more of the preceding claims, characterized by that the cross section of the sun gear (3) and / or the bending element (9) tapers radially inwards. [6] Sun gear according to one or more of the preceding claims, characterized by that the sun gear (3) together with the bending element (9) has a substantially T-shaped and / or double-T-shaped cross-section. [7] Sun gear according to one or more of the preceding claims, characterized by that the T-shaped and / or double-T-shaped cross-section has a base (11) to which the sun gear (3) and / or the bending element (9) are connected to the shaft (2) in a rotationally fixed manner. [8] Sun gear according to one or more of the preceding claims, characterized bythat the sun gear (3) and the shaft (2) are connected to each other in a force-fitting, form-fitting and / or material-fitting manner. [9] Sun gear according to one or more of the preceding claims, characterized by that the shaft (2) is designed as a hollow and / or solid shaft. [10] Sun gear according to one or more of the preceding claims, characterized by that the shaft (2) has a free, unsupported end (6). [11] Sun gear according to one or more of the preceding claims, characterized by that the sun gear (3) is arranged on the shaft (2) in the region of the free end (6). [12] Planetary gear (1) with a central sun gear (3), a ring gear surrounding it and at least two planet gears arranged between these two, which are held by a planet carrier, characterized by that the sun gear (3) is designed according to one or more of the preceding claims. [13] Planetary gear according to the previous claim, characterized by that the sun gear (3) and the planet gears have a play in the radial direction when unloaded.

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