Abstract:
Enclosure for liquid lubricated rotating elements ( 12, 16, 17 ). A first rotating element ( 16 ) with at least one bearing ( 13, 14, 15 ) lubrication fluid drainage point that cooperates with a second rotating element ( 17 ). A partition wall ( 21 ) is mounted between the drainage point and the second element ( 16, 17 ), in such a manner that lubrication fluid is substantially prevented from migrating from the drainage point to the second element.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is a continuation patent application of International Application No. PCT/SE01/02148 filed Oct. 3, 2001 which was published in English pursuant to Article 21(2) of the Patent Cooperation Treaty and which claims priority to Swedish Patent Application No. 0004406-5 filed Nov. 27, 2000. Both applications are expressly incorporated herein by reference in their entireties. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates to an enclosure for liquid lubricated rotating elements, wherein a first rotating element with at least one bearing lubrication fluid drainage point cooperates with a second rotating element.  
           [0004]    2. Background of the Invention  
           [0005]    Turbo units are often used for extracting energy from engine exhaust gases, wherein the turbo unit comprises an exhaust driven turbine which drives a compressor for compressing the intake air supplied to the engine, so called supercharging. A turbo compound unit is sometimes arranged after the turbo unit for extracting some of the remaining energy from the exhaust gases. One example of such a turbo compound unit is a second exhaust driven turbine which e.g. mechanically transfers energy to the drive shaft of the engine or the like.  
           [0006]    The turbo compound unit normally comprises (includes) a shaft in a bearing with a rigidly mounted turbine wheel that can be driven at high speed by the exhausts, e.g. up to about 80,000 rpm. This speed is reduced by means of a gear train; and possibly other methods, down to a considerably lower speed and is transferred to the engine shaft via a fluid coupling which prevents torsional vibration occurring in the engine shaft to be transmitted to the turbine shaft. Normally, a very efficient lubrication of the turbine shaft bearing is needed in order to endure the high rotation speeds that occur. For this object, lubrication oil may be fed with an overpressure of about 1-5 bar to the turbine bearing.  
           [0007]    It appears that the oil leaving the turbine bearing which is supposed to drain down into the crankcase, may hit the fluid coupling which is rotating with high speed, as well as other rotating parts. This results in a formation of a turbulent spray of drops that move in the radial direction outwards until they hit the surrounding surfaces. It has been discovered that these types of oil flows impede the rotation of the fluid coupling, which negatively influences the efficiency.  
         SUMMARY OF INVENTION  
         [0008]    One object of the invention is therefore to provide an enclosure of the rotating fluid lubricated element that avoids the problem described above.  
           [0009]    For this object, the enclosure according to the invention is characterized by a partition wall that is mounted between the drainage point and the second element, in such a manner that lubrication fluid is substantially prevented from migrating from the drainage point to the second element. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]    The invention will be further described in the following, in a nonlimiting way with reference to the accompanying drawing in which:  
         [0011]    [0011]FIG. 1 is a partial cross-section and partial cutaway view taken in the vertical direction through a turbo compound unit configured according to the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]    The turbo compound unit shown in the figure is meant for use in a combustion engine, preferably included in the drive train of a heavy truck or a bus.  
         [0013]    The turbo compound unit comprises a power turbine  11  located in an exhaust channel  10  which turbine is mounted on a turbine shaft  12 . The shaft is mounted by means of a front radial bearing  13 , a rear radial bearing  14  and athrust bearing  15 . Lubrication oil is fed to these bearings via channels with an overpressure in the range of about 1-5 bar. The oil is drained from these bearings via provided draining points.  
         [0014]    A gearwheel  16  is rigidly connected to the shaft  12  and is in mesh with a larger gearwheel  17  that belongs to the primary side of a fluid coupling  18 , that is carried in a combined radial and axial bearing  20  at a front end wall  19  of the turbo compound housing. Thus, rotation energy is transferred from the turbine shaft via the fluid coupling to its secondary side.  
         [0015]    The lubricating oil having passed through the bearings  13 ,  14 ,  15  and being present in front of the gearwheel  17  is intended to flow down along the inside of the front end wall  19  of the turbo compound housing. A partition wall  21 , also referred to as a lubrication shield means, is mounted in the space between the end, wall  19  and the gear wheel  17  by means of, for example, a screw  22 , so that there is a gap  23  between the partition wall and the inside of the end wall  19 . The partition wall  21  is formed by a piece of sheet metal, which is provided with an opening  21  a for the fluid coupling bearing  20  and which otherwise essentially follows the sides of the turbo compound housing with its edges.  
         [0016]    Due to the arrangement of the partition wall  21  in the space between gearwheel  17  and the end wall  19 , the oil may drain into the gap space  23 , without being affected by the turbulence being generated by the rotation of the gear wheel  17 . The comparatively small amount of oil that may hit the gear wheel  17  and be thrown in the direction radially outwards by the wheel, will, among other things, hit the side of the partition wall that is turned towards the gear wheel and can flow down along this surface.  
         [0017]    In order to avoid having oil from the rear radial bearing  14  and the axial bearing  15  hitting the gear wheel  17  or the coupling  18 , or other moving parts, a peripheral shield  24  has been arranged around the fluid coupling  18 , so that the oil may not be forced into the fluid coupling, and instead has to move along the outside of the shield  24  down into the draining space. This shield may at the same time function as blast protection for rotating parts; e.g., the coupling  18 .  
         [0018]    The invention may be alternatively described as a turbo compound unit ( 5 ) of a combustion engine in which the power turbine  11  is driven by gases of the exhaust channel  10 . The turbo compound unit ( 5 ) comprises, or includes, a housing ( 25 ) that encloses at least a portion thereof. The turbo compound unit ( 5 ) further has the driven shaft ( 12 ) that is configured to be rotatably driven by the exhaust driven turbine ( 11 ). Preferably several (a plurality of) bearing sets ( 13 ,  14 ,  15 ), but in any event, at least one bearing set, are arranged about the driven shaft ( 12 ) for holding the shaft ( 12 ) during rotation. The bearing sets ( 13 ,  14 ,  15 ) are pressure lubricated and each have a drain point ( 13   a ,  14   a ,  15   a ) for releasing lubrication after application to the particular bearing set. The first gear ( 16 ) is rotatably operated by the driven shaft ( 12 ) and a second gear ( 17 ) is rotatably operated by the first gear ( 16 ). As illustrated, the first gear ( 16 ), the second gear ( 17 ), the bearing sets ( 13 ,  14 ,  15 ), and the driven shaft ( 12 ) are all commonly enclosed within the housing ( 25 ), and the housing ( 25 ) defines a clear space between the drain points ( 13   a ,  14   a ,  15   a ) of the bearing sets ( 13 ,  14 ,  15 ) and the second gear ( 17 ). A lubrication shield means ( 21 ) is positioned within the housing ( 25 ) for deflecting the released lubrication from the drain points ( 13   a ,  14   a ,  15   a ) away from the second gear ( 17 ) and for improving efficiency of the turbo compound unit ( 5 ) by preventing undesired mass, constituted by the released lubrication, from contacting the second gear ( 17 ).  
         [0019]    In that the driven shaft ( 12 ) is a component of a turbo compound unit ( 5 ), the shaft ( 12 ) is configured to be rotatably driven at speeds exceeding 50,000 revolutions per minute, and preferably at approximately 80,000 revolutions per minute.  
         [0020]    The lubrication shield means ( 21 ) is constructed from sheet material, preferably sheet metal, and is positioned interstitially between the housing ( 25 ) and the second gear ( 17 ). In the illustrated embodiment, the lubrication shield means ( 21 ) is fastened to the housing ( 25 ) with a gap space ( 23 ) therebetween using a threaded member such as a bolt or screw. The gap space ( 23 ) provides a channel within which the released lubrication downwardly drains within the housing ( 25 ) and is partitioned away from the second gear ( 17 ).  
         [0021]    The invention is not limited to the above-described embodiments, but several modifications are possible within the scope of the following claims.