Patent Publication Number: US-2012031704-A1

Title: Device for spray lubrication of a wind turbine transmission

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of German Patent Office application No. 10 2010 033 228.3 filed Aug. 3, 2010, which is incorporated by reference herein in its entirety. 
     FIELD OF INVENTION 
     The present invention relates to a device and a method for spray lubrication of a wind turbine transmission. 
     BACKGROUND OF INVENTION 
     In order to minimize the wear to which a transmission is subject, it is necessary that the individual transmission elements, e.g. the teeth of two intermeshed spur wheels, do not have any direct metal-to-metal contact with each other. For this reason it is important to ensure adequate lubrication, so that all metal surfaces are moistened by a film of oil or lubrication. 
     In the initial phase or after lengthy periods of wind turbine transmissions, there is however the danger that this film does not reach all metal surfaces in sufficient quantities. Because of the lack of a film of lubrication, direct metal-to-metal contact may arise, which results in increased abrasion and wear on the affected transmission parts, e.g. in the form of chatter marks. The risk of transmission failure is thereby increased. 
     In order to meet this problem, oil injection or oil spray devices are used, which squirt or spray the wind turbine transmission with oil shortly prior to its being put back into service, in order to moisten the metal surfaces with a film of oil. Nevertheless, a relatively large number of wind turbine transmissions fail shortly after restart due to inadequate moistening of metal parts with oil. 
     SUMMARY OF INVENTION 
     The object of the present invention is thus to propose a device for spray lubrication of a wind turbine transmission, which enables improved spray lubrication of the transmission parts. 
     This object is achieved by the features of the independent claims. 
     Advantageous developments of the invention are defined in the respective subclaims. 
     The present invention relates to a device for spray lubrication of a wind turbine transmission. The device comprises a transmission enclosed in a housing, a first oil spray unit and a second oil spray unit. Both oil spray units are arranged in the interior of the housing. 
     The first oil spray unit is embodied to spray oil at a first temperature in the interior of the transmission housing and the second oil spray unit is embodied to spray oil at a second temperature in the interior of the transmission housing. The first temperature and the second temperature differ from each other here. 
     The present invention additionally relates to a method for spray lubrication of a wind turbine transmission arranged in a housing, in which at least two oils, which differ from each other in their temperature, are sprayed into the housing. 
     The inventive device and the inventive method have the advantage that the oil particles of the sprayed-in oil move differently because of their different temperature, and thereby distribute themselves better within the housing. This leads to a more even moistening of the transmission parts and thus to better lubrication compared with known devices and methods of this kind. 
     According to one embodiment of the invention, the temperature difference of the sprayed-in oils is here selected in such a way that some of the oil particles rise according to the temperature in the housing and some of the oil particles sink according to the temperature in the housing. The ascending and descending of the oil particles is likewise supported by a corresponding arrangement of the spray units. Through mixing of the rising and falling oil particles an oil mist then arises after the spraying, which moves dynamically within the interior of the housing. This enables a particularly even moistening of the transmission parts with oil, in a simple and cost-effective manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are described by way of example with reference to the attached drawing, in which: 
         FIG. 1  shows the inventive device for spray lubrication of a wind turbine transmission in schematic form. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The inventive device comprises a transmission, which is represented schematically in  FIG. 1  with two spur wheels G 1 , G 2 , two transmission shafts W 1 , W 2  and four bearings L 1 , L 2 , L 3 , L 4 . The transmission G 1 , G 2 , W 1 , W 2 , L 1 , L 2 , L 3 , L 4  is enclosed by a transmission housing, which is not shown. 
     The inventive device further comprises two oil spray devices OS 1 , OS 2 , which together form an oil spray system. The oil spray devices OS 1 , OS 2  are arranged spatially separated from each other on the transmission housing, specifically in such a way that at least their spray head is located within the housing. In a preferred embodiment, the oil spray devices OS 1 , OS 2  are attached to the inside of the transmission housing. 
     As well as the two spray devices OS 1 , OS 2  partly shown in  FIG. 1  further spray devices may belong to the oil spray system. 
     The two oil spray devices OS 1 , OS 2  create oil particles of different diameters. In one embodiment of the invention, the oil spray devices are embodied in such a way that they spray oil particles with a diameter in the range of 1 μm to 20 μm. 
     The oil to be sprayed is pre-heated, in order to attain the desired viscosity. It is then pumped through the oil spray devices OS 1 , OS 2 . It is important here that oil is sprayed out of the oil spray devices at a different temperature. 
     The oil spray devices (OS 1 , OS 2 ) can be arranged at different places on the transmission housing, and spray oil on the transmission from different angles. It is however particularly advantageous if a first oil spray device (OS 1 ) is arranged above and a second oil spray device (OS 2 ) below the moving parts and the oil is sprayed vertically downwards or, as the case may be upwards, in the direction of the transmission parts, in order to achieve a good mixing of the oil particles. 
     This advantageous embodiment is shown in  FIG. 1 . The first oil spray device (OS 1 ) is arranged above the moving parts. It sprays an oil whose temperature lies below the temperature of the oil being sprayed by the second oil spray device. This means that the upper oil spray device sprays the comparatively “cooler” oil. 
     As likewise shown in  FIG. 1 , the second oil spray device (OS 1 ) is arranged below the moving parts of the transmission. It sprays an oil whose temperature lies above the temperature of the oil being sprayed by the first oil spray device (OS 2 ). This means that the lower oil spray device sprays an oil with a comparatively “higher” temperature. 
     In  FIG. 1  the rising of the oil particles with the “higher” temperature as a “heat flow” is indicated by arrows WS pointing upwards. 
     The oil particles sprayed by the first and second oil spray device (OS 1 , OS 2 ) mix in the interior of the transmission housing. As a result of the different temperature and direction of motion of the oil particles an oil mist arises which changes its position within the transmission housing dynamically. 
     In  FIG. 1  this “oil mist” ON is illustrated by arrows arranged in a circle. 
     The temperature difference between the first and second temperature is here selected in such a way that some of the oil particles of the sprayed oil rise and some of the oil particles of the sprayed oil sink, so that the oil mist (ON) forming as a result of the mixing of these ascending and descending oil particles changes its position in the interior of the housing. 
     In one embodiment of the invention, the temperature difference between the first and second temperature lies in the range 40° C. to 60° C. 
     In a preferred embodiment of the invention an oil at a temperature of 40° C. is sprayed by the first oil spray unit (OS 1 ), while an oil at a temperature of 90° C. is sprayed by the second oil spray unit (OS 2 ). 
     The described inventive device and the inventive method enable a more even moistening of the transmission parts with transmission oil compared with known devices and methods of this kind. Use of the inventive device leads to a significantly higher level of operating safety of the transmission of a wind turbine. Downtimes due to repair work and maintenance costs are thereby reduced.