Patent Publication Number: US-9841033-B2

Title: Exhaust gas turbocharger having an internally insulated turbine volute

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a turbine housing of an exhaust-gas turbocharger having an internally insulated turbine volute. 
     Description of the Related Art 
     A turbine housing of this type is known from EP 0 374 603 A1. In the case of said turbine housing, heat insulation is provided in the turbine volute, which heat insulation has a layer of a heat insulation material on which there is arranged a layer of high-temperature-resistant metal. 
     The disadvantage of said arrangement can be seen in the fact that the generally brittle material of the heat insulation layer poses difficulties with regard to installation. 
     By contrast, it is an object of the present invention to provide a turbine housing according to the preamble part of claim  1  having a heat insulation layer that can be easily installed in the turbine volute of the turbine housing. 
     BRIEF SUMMARY OF THE INVENTION 
     This object is achieved by a turbine housing of an exhaust-gas turbocharger having a turbine volute with a metallic outer shell, a heat insulation layer formed as a separate component placed into the turbine volute, the heat insulation layer having a heat insulation core and two sheet-metal shells that encase the heat insulation core. 
     By virtue of the heat insulation layer being formed as a separate component which, after being produced, can be placed into the turbine volute of the turbine housing, the installation process is simplified considerably, resulting in an associated reduction of the overall production outlay for the turbine housing according to the invention. 
     The heat insulation core is in this case preferably formed as an insulator part, in particular as a ceramic core. 
     The dependent claims contain advantageous developments of the invention. 
     The provision of two sheet-metal shells that encase the heat insulation core yields the advantage that the heat insulation core is enclosed on all sides, such that the heat insulation material, even if brittle, is held securely by the encasement. Furthermore, the provision of the first and second sheet-metal shells, which are preferably of very thin-walled form, has the effect that the heat insulation layer has a low heat capacity, which advantageously results in fast heating of the surface of the turbine volute, such that, during operation, the turbine housing no longer constitutes a heat sink that would impair the cold-start characteristics of an engine equipped with an exhaust-gas turbocharger. 
     It is preferably possible for the heat insulation layer to be divided into two insulation components which each have a heat insulation core which is surrounded by the first and second sheet-metal shells. 
     Here, the sheet-metal shells may be connected to one another, with a welded connection being particularly advantageous for this purpose. 
     The heat insulation components may be fixed within the turbine volute by means of a press-on part, which either is a separate pressed part or may be formed by the rear wall of a bearing housing which is connected to the turbine housing according to the invention in order to form an exhaust-gas turbocharger according to the invention. 
     It is particularly preferable for elevations to be provided on the inner wall of the turbine volute, which elevations firstly make it possible to realize dimensional and position tolerancing and furthermore make it possible to realize an additional insulating or heat insulation layer between the inner wall of the turbine volute and the heat insulation layer. Said additional insulation or insulating layer may for example be an air layer. 
     Here, the elevations may be produced either during the course of the casting of the turbine housing or, after the casting of the turbine housing, by cutting machining processes. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further details, advantages and features of the present invention emerge from the following description of exemplary embodiments with reference to the drawing, in which: 
         FIG. 1  shows a schematically simplified illustration of one half of a turbine housing according to the invention, 
         FIG. 2  shows a perspective illustration of the turbine housing according to the invention, 
         FIG. 3  shows a plan view of the turbine housing, 
         FIGS. 4 and 5  show schematically highly simplified diagrammatic illustrations of the turbine housing according to the invention, for explanation of the possible position of parting planes, and 
         FIG. 6  shows a schematically highly simplified diagrammatic illustration of an exhaust-gas turbocharger according to the invention that can be provided with the turbine housing according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows, in the illustration selected in  FIG. 1 , an upper half of a turbine housing  1  according to the invention, which turbine housing may be part of an exhaust-gas turbocharger  15  according to the invention illustrated in  FIG. 6 . 
     The turbine housing  1  has a turbine volute  7  which is delimited by a metallic outer shell  8 . The metallic outer shell  8  may for example be a cast component and has an inner wall  9 . 
     In the turbine volute  7  there is arranged a heat insulation layer  10 , which in the exemplary embodiment illustrated in  FIG. 1  is divided into two insulation components  10 A and  10 B. Each of the insulation components  10 A and  10 B has an associated heat insulation core  6 A and  6 B respectively, which heat insulation cores may be produced from a suitable material, in particular a fibrous material or ceramic material. 
     Each of the heat insulation cores  6 A,  6 B is enclosed by an arrangement of two sheet-metal shells  3 A and  3 B, and  4 A and  4 B, respectively. Here, the sheet-metal shells  3 A and  3 B are arranged adjacent to a volute interior space  11  and accordingly form the flow-guiding surfaces during the operation of the turbine housing  1 . In the installed state, the sheet-metal shells  4 A and  4 B are arranged adjacent to the inner wall  9  and serve for fixing the insulation components  10 A and  10 B in the turbine volute  7 . 
     As shown in detail in  FIG. 1 , the sheet-metal shell  3 A bears against a surface  12 A, which points toward the volute interior space  11 , of the heat insulation core  6 A. The sheet-metal shell  4 A bears against a surface  13 A, which points toward the inner wall  9 , of the heat insulation core  6 A. The encasement on all sides by the sheet-metal shells  3 A and  4 A results in the stabilization of the heat insulation core  6 A explained in the introduction, and prevents parts of said heat insulation core  6 A from passing into the turbine volute  7 . 
     Correspondingly, the heat insulation core  6 B is constructed such that the shell  3 B accordingly bears against the surface  12 B and the shell  4 B bears against the surface  13 B and against a further surface  13 ′B which is arranged adjacent to a press-on part  2 . The insulation components  10 A,  10 B, which after being produced (independently of the turbine housing  1 ) are placed into the turbine volute  7 , can be fixed in the turbine volute  7  by means of said press-on part  2 . 
     Here, the press-on part  2  may be a separate press-on part or may be the rear wall of a bearing housing such as the bearing housing  17 , illustrated in  FIG. 6 , of the exhaust-gas turbocharger  15 . 
     The particularly preferred embodiment illustrated in  FIG. 1  also has elevations  5 ,  5 ′ and  5 ″ which are formed on the inner wall  9  so as to point in the direction of the volute interior space  11 . As a result of the provision of said elevations  5 ,  5 ′ and  5 ″, the heat insulation core  6 A, when in the installed state, bears by way of its outer shell  4 A against said elevations  5 ,  5 ′ and  5 ″. This yields the advantage that three further insulating or insulation layers  21 A,  21 B and  21 C are created, which further insulating or insulation layers may for example be filled with air and yield thermal decoupling between the turbine volute  7 , or the outer shell  8  thereof, and the heat insulation core  6 A. 
     For the production of the turbine housing  1  according to the invention, said turbine housing is initially cast, and the heat insulation layer  10 , or the insulation components  10 A and  10 B thereof, are manufactured separately in the manner explained above. It is self-evident here that, in principle, it is also possible for the heat insulation layer  10  to be divided not only into two insulation components, as shown in  FIG. 1 , but also into multiple such insulation components, which can then be assembled and fixed in the turbine volute  7 . Furthermore a single, unitary heat insulation layer  10  is also conceivable. 
     After the arrangement of the insulation components  10 A and  10 B, said insulation components are fixed in the turbine volute  7  by the pressing-on of the press-on part  2 , wherein a seal  14 , for example in the form of a V-section seal, may preferably be provided between the press-on part  2  and the outer shell  8  of the turbine volute  7 . 
       FIG. 2  shows the turbine housing  1  according to the invention in a perspective illustration in order to illustrate the possible position of the elevations  5 ,  5 ′,  5 ″ and  5 ′″ already described with regard to  FIG. 1 . In this respect, reference is hereby explicitly made to the diagrammatic illustration of  FIG. 2 . 
       FIG. 3  shows a possible eccentric arrangement E of the turbine housing axis A 2  with respect to the bearing housing axis or press-on part axis A 1 , which arrangement reduces the space requirement because the uneven space requirement of the turbine housing in the radial direction owing to a spiral shape is partially compensated. 
       FIGS. 4 and 5  are schematically highly simplified illustrations of the turbine housing  1 , which in these illustrations has a split turbine volute divided into turbine volute parts  7 A and  7 B. Here, the respective undercut-free parting planes TE are indicated in  FIGS. 4 and 5 . The turbine volute parts  7 A and  7 B may be connected to one another in a suitable manner, for example by means of screw connections or by means of welded connections. 
       FIG. 6  is a schematically highly simplified illustration of the above-mentioned exhaust-gas turbocharger  15  according to the invention having the turbine housing  1  which may be designed in accordance with the principles explained above on the basis of  FIGS. 1 to 5 . As is conventional, the turbine housing  1  accommodates a turbine wheel  16  which is arranged on one end of a shaft  18 , on the other end of which shaft there is arranged a compressor wheel  20  which is arranged in a compressor housing  19 . Here, the shaft  18  is mounted in the usual way by means of the bearing housing  17 . 
     In addition to the above written disclosure, reference is hereby explicitly made, for supplementation thereof, to the diagrammatic illustration of the invention in  FIGS. 1 to 6 . 
     LIST OF REFERENCE SIGNS 
     
         
           1  Turbine housing 
           2  Press-on part 
           3 A,  3 B Inner sheet-metal shells 
           4 A,  4 B Outer sheet-metal shells 
           5 ,  5 ′,  5 ″,  5 ′″ Elevations 
           6 A,  6 B Heat insulation core 
           7  Turbine volute 
           7 A,  7 B Turbine volute parts 
           8  Outer shell 
           9  Inner wall 
           10  Heat insulation layer 
           10 A,  10 B Insulation components 
           11  Volute interior space 
           12 A,  12 B,  13 A,  13 B,  13 ′B Surfaces of the heat insulation cores  6 A,  6 B 
           14  Seal 
           15  Exhaust-gas turbocharger 
           16  Turbine wheel 
           17  Bearing housing 
           18  Shaft 
           19  Compressor housing 
           20  Compressor wheel 
           21 A,  21 B,  21 C Isolation or insulation layers 
         L Longitudinal axis of the exhaust-gas turbocharger 
         E Eccentricity 
         A 1  Bearing housing axis or press-on part axis 
         A 2  Turbine housing axis 
         TE Undercut-free parting planes