1. Field of the Invention
The invention relates to a planetary gear with a stationary ring gear, a rotatable planet carrier having at least two planet wheels, and a sun gear.
The invention relates in particular to a gear for a wind power plant.
2. Discussion of the Prior Art
The trend that continues for wind power plants to construct relatively compact and light units leads to components installed in the wind power plants being exposed to increasingly larger deformations even in load-transmitting parts. In particular under dynamic loads, larger deformations above all of bearings and gear parts lead to locally excessive tensions that are partly inadmissibly strong in places, that again result in a marked reduction in the life of the components. For bearings and gear gears, a toothing offset or a trajectory deviation of the rolling elements of as little as 10 to 25 μm as a result of tilting due to external forces and moments can lead to an excessive load of such a magnitude that the components fail even after a very short time and thus lead to considerable financial damage.
On top of this, a wind power plant has an increased noise level due to the non-uniform engagement of the gear wheels into each other that is undesirable in particular in populated areas.
In particular for wind power plants of the 2.5 to 6 MW class, rotor bearings and ring gears of planet wheel have an outside diameter of approximately 2.5 to 3.5 m and widths of approximately 350 to 500 mm, the large teeth width leading to problems in terms of a uniform engagement of the toothing across the entire width of the teeth, in particular when outside loads act on this component. It is therefore necessary for the planet wheels to be able to give way to the deformation that is forced on them, above all tilting about the axes at right angles to the axis of rotation of the planet wheel, so that the teeth can engage as best as possible, that is to say uniform, across the tooth width in all load situations.
Due to the one-sided torque transmission via the planet wheel, the planet carrier is twisted. This leads to the axes of rotation of the planet wheel being shifted and thus to the tooth-engaging load to be less uniform across the entire tooth width, so that the gears can no longer transmit the forces in an evenly distributed manner. This leads to local excess loads and wear of the toothing that can be partly countered in the known planet wheels by tooth corrections.
As a further remedy, a planetary gear is for example known from DE 103 18 945 B3 where the planet axes are firmly connected to the gear wall and the planet wheels are mounted such on the planet axes that they tumble.
To mount the planet wheels, also the elements known from US 2008/0153657 A1 as “Flexpins” can be used.
However, this design of a planetary gear is also accompanied by increased assembly efforts despite increased manufacturing tolerances because each planet wheel has to be set up precisely and checked in terms of its functioning, i.e. its uniform engagement with the ring gear and the sun gear.