Patent Application
20160215873
This application claims priority to German patent application no. DE 10 2015 201 171.2 filed on Jan. 23, 2015, the contents of which are fully incorporated herein by reference.
The disclosure is directed to a driveline located between a rotor and a generator of a wind turbine, the driveline including a planetary gear unit that includes a planet carrier. The planet carrier is rotatably supported relative to a housing part by at least one rolling-element bearing having at least one inner ring, at least one outer ring, and rolling elements between the inner and outer rings.
A wind turbine requires a driveline in order to conduct the torque generated by a rotor at its hub to a generator in a process that allows electrical energy to obtained from wind energy. For this purpose the rotation of the rotor must be translated, and a planet gear unit can be used for this purpose. An example of a planetary gear unit of a wind turbine is described in DE 10 2012 214 023 B3, a family member of U.S. Pat. No. 9,115,800, and U.S. Pat. No. 9,115,800 is hereby incorporated by reference.
In order to support a planet carrier of a planetary gear unit in wind power applications, full complement cylindrical roller bearings (or sometimes tapered roller bearings) are generally used. One of the principal reasons for using full complement bearings is that they require no cage and are thus more cost-effective than bearings that require cages. This can be particularly advantageous in view of the large size of the bearings generally required for wind turbines.
However, when full complement bearings are used, there is a risk of “smearing.” Smearing occurs when two inadequately lubricated surfaces slide against each other under load and material is transferred from one surface to the other. The sliding surfaces involved may become scored and develop a “torn” appearance. When smearing occurs, the material is generally heated to such temperatures that re-hardening takes place. This produces localized stress concentrations that may cause cracking or flaking. Smearing is undesirable in wind turbine applications and may result in the rolling elements and possibly also the bearing rings becoming black oxidized. This in turn has a negative effect on cost.
A further disadvantage of full complement bearings is that these bearings are separable, that is, the individual parts of the bearing are only held together when the bearing is installed. If the shaft or the inner ring is removed, the individual bearing elements, such as the rollers, are prone to falling out of the bearing assembly.
In contrast, the high load rating that can be achieved by a full complement bearing is usually not needed in the above-described application.
An aspect of the disclosure is to provide a driveline having a planetary gear unit of the above-described type. This allows the bearing assembly to be embodied more cost-effectively, while still providing a sufficient stability of the bearing. Furthermore, the installation and removal of the bearing assembly is possible in a simpler manner than is the case when full complement bearings are used.
The disclosure involves disposing a spacer element between each two adjacent pairs of rolling elements. The spacer element includes running surfaces for the two adjacent rolling elements, and, viewed from the spacer elements, the region between the bearing rings is free from further cage elements.
The spacer element is preferably comprised of plastic, preferably polyether ether ketone (PEEK). The spacer element is preferably manufactured by injection molding.
The rolling elements preferably have a hardened and ground surface, which, however, is free from black oxidation.
The spacer element can be disposed between the bearing rings such that it lies with its radially inner-lying end radially below the bearing pitch circle and with its radially outer-lying end radially above the bearing pitch circle. This helps hold the bearing elements together even when the inner ring or shaft is removed.
The spacer elements can be connected to one another by a connecting element such as a cord or a cable. This helps prevent the bearing parts from falling apart during the partial removal of bearing parts and improves the connection between the parts.
The rolling-element bearing is preferably configured as a cylindrical roller bearing.
However, embodiments using tapered roller bearing are also possible. In such an embodiment, two axially spaced tapered roller bearings would be axially preloaded against each other.
The disclosure thus avoids the costs caused by black oxidized rolling elements (rollers). Instead, a cage-spacer piece (spacer) made from a suitable material for holding and guiding the rolling elements is used without using a cage. In this regard, the material PEEK has proven particularly useful. Advantageously the cage-spacer piece prevents smearing from occurring.
Furthermore, the presence of the cage-spacer pieces reduces the number of expensive rollers that are required for a bearing of a given diameter. Because the plastic spacers are less expensive that rollers, the cost of the bearing is reduced.
Another aspect of the disclosure comprises a driveline configured to connect a wind turbine rotor and a wind turbine generator. The driveline includes a planetary gear unit having a planet carrier rotatably supported relative to a housing part by at least one cage-less rolling-element bearing. The cage-less rolling-element bearing includes at least one inner ring and least one outer ring, and a plurality of rolling elements disposed between the at least one inner ring and the at least one outer ring. The rolling element bearing further includes a spacer element disposed between adjacent pairs of the plurality of rolling elements, the spacer elements each having first and second running surfaces for guiding one of the plurality of rolling elements. A further aspect of the disclosure comprises a similar driveline that includes spacer means.
A further advantage is that with the disclosed design of the planet-carrier bearing the bearing can be better held together by suitable construction of the spacer piece (i.e. of the spacer). Thus the handling, and optionally the bearing control and assembly, can be improved and simplified.
An exemplary embodiment of the invention is depicted in the drawings:
In
The design of a planetary gear unit is well known and will not be described further herein. However, a suitable planetary gear unit is shown in the aforementioned DE 10 2012 214 023 B3, and various embodiments can be found therein.
The design of the rolling-element bearing 4 can be seen in
The spacer elements 6 are comprised of plastic and as such are known as spacers in rolling-element bearings. For this purpose DE 10 2011 087 864 A1 of the applicant is referred to and expressly referenced, which shows general cage segments of a similar type. This document is a family member of US 2015/0078699, and US 2015/0078699 is hereby incorporated by reference.
Each spacer element 6 includes lateral running surfaces 7 and 8 that are configured to be complementary to the shape of the rolling elements 5. As can be seen from
Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved drivelines for wind turbines.
Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.
All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 201 171.2 | Jan 2015 | DE | national |
