Abstract:
A turbomachine, particularly an exhaust gas turbocharger, comprising a compressor wheel arranged in a compressor housing, a turbine wheel arranged in a turbine housing, and a rotor shaft which is guided in a bearing casing and which has fastened thereto the compressor wheel on the one hand and the turbine wheel on the other hand, a rotor-shaft seal being arranged between a turbine-sided end portion of the bearing casing and the rotor shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to European Patent Application No. 05002505.5 filed Feb. 7, 2005.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a turbomachine, particularly an exhaust gas turbocharger.  
       BACKGROUND OF THE INVENTION  
       [0003]     Such a turbomachine in the form of a turbocharger is known from US 2004/0120835 A1.  
         [0004]     U.S. Pat. No. 4,453,722 discloses a carbon seal which is pressed by a bellows against a seal plate, and a back-up seal is additionally provided which consists of a piston ring intended to maintain its bias even if the bellows fails.  
         [0005]     A further turbomachine in the form of a turbocharger is known from DE 100 28 161 C2 and DE 102 97 203 T5.  
         [0006]     The sealing which can be seen there at the turbine side between rotor shaft and bearing casing is accomplished by means of a labyrinth seal.  
         [0007]     Leakage is thus possible both in the direction of the turbine wheel and in the direction of the bearing casing.  
         [0008]     In comparison with this prior art, it is the object of the present invention to provide a turbomachine which allows a better sealing of chambers acted upon by media, such as liquids and/or gases of different pressures.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, the present invention relates to a turbomachine, particularly in the form of an exhaust gas turbocharger, e.g. for automotive vehicles, comprising a rotor-shaft sealing system provided at the turbine side, which may preferably be configured in the form of a gas-lubricated slide ring seal. Said rotor-shaft sealing system permits the sealing of chambers which are acted upon by media (liquids and/or gases) which are subjected to different pressures, with a rotating shaft, which in the case of a turbocharger is a rotor shaft, being guided through a housing wall. The turbomachine of the invention or the rotor-shaft sealing system of the invention is suited for high temperatures (up to 900° C.) and extremely high speeds (up to 300,000 m −1 ) and circumferential speeds up to 550 m/s.  
         [0010]     Furthermore, a rotating counter ring (with profile) is fixed to the rotor shaft, which can e.g. be accomplished by shrinking, screwing or pressing. Furthermore, a stationary slide ring with resilient means, preferably in the form of a metal diaphragm bellows, is screwed via a screw-in sleeve in the housing. During operation of the turbocharger, the counter ring together with the slide ring represents the dynamic seal and the metal diaphragm bellows with the graphite ring constitutes the static seal.  
         [0011]     The metal diaphragm bellows represents a biasing means which establishes a resilient contact. Preferably, it is here possible to weld the individual resilient elements of the bellows together and then to the welding lips provided for this purpose on an adapter plate of the screw-in sleeve. Hence, it is advantageously possible to pre-mount said member of the whole sealing means already as a cartridge. During mounting of the cartridge a bias is observed in the metal diaphragm bellows, so that axial play and possible wear of the slide surfaces can advantageously be minimized.  
         [0012]     When the turbocharger is at a standstill, the counter ring and the slide ring form a static seal between rotor shaft and bearing casing.  
         [0013]     During operation of the turbocharger the rotation of the counter ring builds up pressure due to the axial profile thereof in the contact surface with the slide ring, resulting in the formation of a small axial gap.  
         [0014]     During operation this creates a contactless, gas-lubricated dynamic slide ring seal which does not cause any mechanical frictional losses.  
         [0015]     The profile of the counter ring has been chosen such that leakage (gap flow) from the turbine wheel into the interior of the bearing casing is supported.  
         [0016]     The present invention as a further embodiment also includes an inventive rotor-shaft sealing means as an independently tradable member.  
         [0017]     The present invention is a preferred embodiment also includes a method for producing a turbomachine with a rotor-shaft sealing means, the method including the following steps:  
         [0018]     inserting the graphite ring into the bearing casing;  
         [0019]     mounting the counter ring on a mounting mandrel and insertion into the bearing casing;  
         [0020]     screwing the cartridge with slide ring and resilient means with the help of a tool, which grips into bores provided therefor in the screw-in sleeve, into the bearing casing, and resulting pressing of the graphite ring;  
         [0021]     sliding a heat shield onto the rotor shaft; and  
         [0022]     introducing the rotor shaft into the bearing casing, the counter ring being pressed with the help of the mounting mandrel onto the rotor shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     Further details, advantages and features of the present invention become apparent from the following description of an embodiment with reference to the enclosed drawing, in which  
         [0024]      FIG. 1  shows a longitudinal section through a turbomachine of the invention in the form of a turbocharger; and  
         [0025]      FIG. 2  shows detail X in  FIG. 1  on an enlarged scale for explaining the constructional details of the inventive rotor-shaft sealing means. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIG. 1  shows a turbomachine  1  of the invention, which in this example is configured as an exhaust gas turbocharger.  
         [0027]     Apart from the following details of a rotor-shaft sealing means  8  according to the invention, this exhaust gas turbocharger contains, as a matter of course, all of the standard components which, however, are partly not shown for simplifying the illustration in  FIG. 1  because these are not needed for explaining the present invention.  
         [0028]     However,  FIG. 1  shows the rear wall  2  of a compressor housing (not shown) and a compressor wheel  3  arranged in said compressor housing.  
         [0029]     Furthermore, a turbine wheel (rotor)  4  is shown, which is arranged in a turbine housing (not shown).  
         [0030]     The compressor wheel  3  and the turbine wheel  4  are mounted on a rotor shaft  6  at opposite ends thereof, as follows in detail from  FIG. 1 .  
         [0031]     The rotor shaft  6  is guided via a suitable bearing arrangement in a bearing casing  5 .  
         [0032]     The bearing casing  5  comprises an end portion  7  provided at the turbine side, which is arranged in the vicinity of the turbine wheel  4  and which is protected by a heat shield  26  from excessive heating.  
         [0033]     The end portion  7  at the turbine side comprises a receiving chamber  30  for a rotor-shaft sealing means  8  which is marked in  FIG. 1  with detail X and which will be explained in detail in the following with reference to the enlarged illustration of  FIG. 2 .  
         [0034]     The rotor-shaft sealing means  8  is constructed as a gas-lubricated slide-ring sealing means which comprises a static sealing arrangement and a dynamic sealing arrangement.  
         [0035]     In detail, a counter ring  11  is provided which comprises a fixing section  12  which can be fixed (shrunk, screwed or pressed) onto a first rotor-shaft area  9 .  
         [0036]     Furthermore, the counter ring  11  comprises an annular collar  13  which is preferably arranged at a right angle to the fixing section  12  and which partly axially rests on a transition area  31  of the rotor shaft  9  which leads to a second rotor shaft area  10  having a larger diameter than the first rotor shaft area  9 .  
         [0037]     The rotor-shaft sealing means  8  further comprises a slide ring  15  which is screwed with a biasing means, preferably in the form of the illustrated metal diaphragm bellows  19 , via a screw-in sleeve  20  with external thread  27  in the bearing casing  5  or in the end section  7  of the bearing casing  5 .  
         [0038]     As illustrated, the slide ring  14  comprises a main body  16  and a nose  15  which extends radially outwards from the main body  16 . This arrangement provides a contact surface which faces the collar  13  of the counter ring  11  and gets into contact with said collar, as illustrated in  FIG. 2 , in the mounted state.  
         [0039]     Furthermore,  FIG. 2  illustrates a graphite ring  18  which is clamped in the casing  5  in the screwed-in state of the screw-in sleeve  20 .  
         [0040]     An adapter plate  17  which is firmly connected to the slide ring  14  is arranged between the slide ring  14  and the arrangement consisting of screw-in sleeve  20  and metal diaphragm bellows  19 .  
         [0041]     At the opposite end, the adapter plate  17  comprises a welding lip  24  which has welded thereto a resilient member  23  of a resilient arrangement consisting of the resilient members  21 ,  22  and  23  of the metal diaphragm bellows  19 .  
         [0042]     The resilient member  21 , in turn, is welded to a welding lip  25  of the screw-in sleeve  20 .  
         [0043]     As has already been explained above, the individual resilient members  21  to  23  of the bellows  19  which are welded together, the adapter plate  17  and the screw-in sleeve  20 , as well as the slide ring  14  constitute a pre-mountable cartridge. Upon installation of said cartridge a bias of the slide ring  14  is produced by the metal diaphragm bellows  19 , so that the axial play and possible wear of the slide surfaces can be minimized. Finally, as follows from  FIG. 2 , the adapter plate  17  comprises an annular body  29  which is arranged around the rotor shaft section  10  of the rotor shaft  6  and which is provided at its radially outwardly oriented end with the welding lip  24  and the connecting section  28 .  
         [0044]     As illustrated in  FIG. 2 , the connecting section  28  rests on both the nose  15  and the main body  16  of the slide ring  14 , whereas the ring body  29  rests on the main body  16  of the slide ring  14 . As for further details of the arrangements of the above-described members, explicit reference is herewith made to the graphic disclosure in  FIG. 2 .  
         [0045]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.