Patent Publication Number: US-2023147046-A1

Title: Turbine housing for an exhaust gas turbocharger

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority pursuant to 35 U.S.C. 119(a) to German Patent Application No. 202021106090.5 filed Nov. 8, 2021, which application is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The invention relates to a turbine housing for an exhaust turbocharger. 
     An exhaust turbocharger comprises a turbine and a compressor. The turbine converts energy from exhaust gas into mechanical energy for driving a compressor. The turbine, driven by the exhaust gas of an internal combustion engine, supplies driving energy for the compressor in that the exhaust gas drives a turbine wheel of the turbine, the rotation of the turbine wheel by way of the shaft being transmitted to a compressor wheel of the compressor, the latter compressing air for the internal combustion engine. 
     The turbine of the exhaust turbocharger comprises a turbine housing which receives the turbine wheel and in which the latter rotates. In a radial turbine, the inflow takes place in the radial direction from the outside to the inside, and the outflow takes place in the axial direction. The turbine housing on the rear side is connected to a bearing housing in which the shaft that drives the compressor rotates. 
     A conventional turbine housing comprises a spiral volute by way of which entering exhaust gas is directed about the turbine wheel, and an arcuate volute outlet gap which runs about the turbine wheel and through which the exhaust gas flows from the volute to the turbine wheel. A B-type volute has a cross section with a straight rear side and an arcuate front side which extends in an outlet direction of the exhaust gas, wherein the straight rear side opens into a straight, or radially running volute outlet gap such that a substantial proportion of the turbine housing material is concentrated on the rear side of the turbine housing that faces the bearing housing. As a result of the design of the turbine housing with a straight rear wall interior as described above, a direct inflow of the exhaust gas results on that side of the turbine housing that faces the bearing housing. 
     SUMMARY 
     The object is based on providing an improved turbine housing. 
     The object is achieved by a turbine housing having the features of claim  1 . 
     The turbine housing for an exhaust turbocharger is configured for receiving a turbine wheel that is rotatable about an axis. The turbine housing comprises an exhaust gas inlet, an axial exhaust gas outlet pointing in an outlet direction, and a single-flow, spiral exhaust gas routing having a volute and a volute outlet gap, the latter being configured so that exhaust gas flows from the volute to the turbine wheel, wherein the exhaust gas routing is fluidically connected to the exhaust gas inlet and is defined by an internal wall of the turbine housing. The volute has a portion which encircles the axis and has a convexity of the internal wall, in that the convexity, counter to the outlet direction, extends beyond the volute outlet gap, and in that sectional faces through which the axis runs each have a volute contour with a straight linear portion, wherein the straight linear portion conjointly with the axis defines an angle facing the exhaust gas outlet that is less than or equal to 90°. 
     The outlet direction advantageously runs parallel to the axis about which the turbine wheel rotates. The turbine housing has a funnel-shaped exhaust gas inlet which is fluidically connected to an exhaust gas routing such that the exhaust gas flows through the exhaust gas inlet into the exhaust gas routing. The exhaust gas routing is single-flow, which is also referred to as a “monoscroll”. The exhaust gas routing extends in the shape of a spiral about a central region in which the turbine wheel is received. The volute outlet gap runs in the shape of a ring or an arc and connects the central region for the turbine wheel to the volute such that the exhaust gas guided about the turbine wheel can flow radially onto the turbine wheel and as a result can drive the latter. The volute outlet gap advantageously runs in a plane that is perpendicular to the axis. The volute outlet gap extends radially, and in an arcuate manner encircles the axis. Vanes for directing the exhaust gas flow can be provided in the volute outlet gap. The vanes can be adjustable. 
     The convexity counter to the outlet direction is an extent of the volute in the direction of the bearing housing, the latter being able to be connected to the turbine housing. In comparison to the volute of a conventional embodiment, this axial deformation permits a smaller extent of the volute in the radial direction, i.e. perpendicular to the axis, without the performance of the embodiment according to the invention being reduced in comparison to the conventional embodiment. This is associated with a smaller installation size, a smaller radial extent and a lower weight of the turbine housing according to the invention, as is constantly desired by customers. Nevertheless, already existing specifications and standards and production methods can be maintained despite the smaller installation size, while simultaneously maintaining or improving the performance. 
     The volute in the portion having the convexity also has a flattened region on its rear side that faces away from the exhaust gas outlet. A straight linear portion of a volute contour is in this region, whereby the straight linear portion runs from the convexity so as to be perpendicular to the axis, or in particular runs from the convexity so as to be angular in relation to the axis, such that the straight linear portion is inclined in relation to the exhaust gas outlet. The volute contour is the line of the internal wall in a section through the exhaust gas routing such that the axis runs through the sectional face. While there are two volute contours in such a plane, the two volute contours do not necessarily have to lie within the portion and do not necessarily have to have a straight linear portion. 
     The straight linear portion is advantageously a region of the volute contour that faces away from the exhaust gas outlet, such that the straight linear portion faces the bearing housing and the region of the volute contour that faces the exhaust gas outlet is radiused. The straight linear portions shape the flattened region on the rear side of the volute. The flattened region advantageously influences the flow behavior of the exhaust gas. The straight linear portion can run on a side of a line that faces away from the exhaust gas outlet and that runs along a region of a volute outlet gap contour perpendicularly to the axis such that the straight linear portion is entirely or partially to the rear of the line. This line can in particular run along a region of a volute outlet gap contour that faces away from the exhaust gas outlet such that the straight linear portion beyond the volute outlet gap is on the side of the housing that faces the bearing housing. The flattened region thus runs at the rear of the volute outlet gap. The volute contour beyond the volute outlet gap and the straight linear portion is advantageously configured so as to be radiused. 
     A coupling device is advantageously provided on the rear side of the turbine housing, the coupling device being disposed so as to face away from the exhaust gas outlet and configured for connecting the turbine housing to a bearing housing. 
     In one embodiment, the portion which encircles the axis and has the clearance and the flattened region extends in an arcuate manner between a beginning and an end, wherein the beginning and the end between the axis define an angle of at least 90°, in particular at least 120° and most particularly at least 180°. The region having the convexity thus extends along a major part of the exhaust gas routing but not necessarily up to the end of the latter. The beginning of the region can be directly after the exhaust gas inlet proceeding from which the exhaust gas routing extends. 
     In one embodiment, a length of the straight linear portion decreases as the encirclement of the axis increases, such that the flattened region tapers as the encirclement increases. A depth by way of which the convexity extends beyond the volume outlet gap can also decrease as the encirclement of the axis increases. In an embodiment of an exhaust gas routing that is encircling up to a tongue, the volute contour in a sectional face on the tongue end region through which the axis runs would in this instance no longer have a straight linear region, or no longer have a convexity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A few exemplary embodiments will be explained in more detail hereunder by means of the drawing. In the drawing: 
         FIG.  1    shows a schematic illustration of an exhaust turbocharger; 
         FIG.  2    shows a sectional illustration through an exemplary embodiment of a turbine housing; 
         FIG.  3    shows a further sectional illustration through the turbine housing; 
         FIG.  4    shows a sectional illustration through an exemplary embodiment of an exhaust gas routing; 
         FIG.  5    shows exemplary embodiments of volutes of an exemplary embodiment according to the invention and of a conventional exemplary embodiment in a schematic sectional illustration; and 
         FIG.  6    shows exemplary embodiments of volutes of an exemplary embodiment according to the invention and a conventional exemplary embodiment in a further schematic sectional illustration. 
     
    
    
     In the figures, identical or functionally equivalent components are provided with the same reference signs. 
     DETAILED DESCRIPTION 
       FIG.  1    shows a schematic illustration of an exhaust turbocharger having a turbine wheel  3  and a compressor wheel  5 , the turbine wheel  3  and the compressor wheel  5  being connected by way of a shaft  1 . The exhaust turbocharger comprises a bearing housing  7 , a turbine housing  9  and a compressor housing  11 . The turbine housing  9  receives the turbine wheel  3 , the compressor housing  11  receives the compressor wheel  5 , and the shaft  1  is rotatably mounted in the bearing housing  7 . The turbine housing  9  as well as the compressor housing  11  have spiral volutes  13 ,  15  by way of which exhaust gas is guided to the turbine wheel  3 , or compressed air is discharged from the compressor wheel  5 , respectively. 
     A turbine, driven by exhaust gas of an internal combustion engine, supplies driving energy for a compressor. The exhaust gas of the internal combustion engine drives the turbine wheel  3 , the rotation of the latter by way of the shaft  1  being transmitted to the compressor wheel  5 , the rotation of the latter compressing air supplied to the internal combustion engine. The exhaust gas by way of the volute  13  flows radially onto the turbine wheel  3  and is axially output through an exhaust gas outlet  17 . The air flows axially onto the compressor wheel  5  and is discharged radially by way of the volute  15  and then guided to the internal combustion engine. 
       FIG.  2    shows a sectional illustration through an exemplary embodiment of a turbine housing  9  which in the central region  21  thereof is configured for receiving a turbine wheel  3  (not illustrated in  FIG.  2   ) that is rotatable about an axis  19 . The axis  19  runs perpendicularly to the drawing plane. 
     The turbine housing  9  has an exhaust gas inlet  23 , an exhaust gas routing  25  and an exhaust gas outlet  17 . The exhaust gas inlet  23  is a funnel-shaped region through which exhaust gas flows into the turbine housing  9 . The exhaust gas inlet  23  transitions to the single-flow, spiral exhaust gas routing  25  such that the exhaust gas inlet  23  and the exhaust gas routing  25  are fluidically connected. The exhaust gas inlet  23  as well as the exhaust gas routing  25  are formed by internal walls  35  of the turbine housing  9 . The exhaust gas routing  25  in the shape of a spiral encircles the axis  19  and winds itself once about the central region  21  for the turbine wheel  3 . An end region of the exhaust gas routing  25  which is wound about the central region  21  is separated from the funnel-shaped exhaust gas inlet  23  by a tongue  27 . The tip of the tongue defines the transition from the exhaust gas inlet  23  to the exhaust gas routing  25 , the transition in  FIG.  2    being in the upper region of the line A-A. A cross section of the exhaust gas routing  25  tapers in the encirclement, wherein the cross section is in a sectional plane through which the axis  19  runs. The exhaust gas routing has a volute  14  and, between the volute  13  and the central region  21 , an annular volute outlet gap  29  such that the exhaust gas can flow through the volute outlet gap  29  onto the turbine wheel  3 . The exhaust gas outlet  17  extends axially to the central region  21  and is configured for discharging the exhaust gas once the latter has flowed across the turbine wheel  3 . 
       FIG.  3    shows a schematic sectional illustration through the turbine housing  9  along a line A-A which is illustrated in  FIG.  2   . 
     The turbine housing  9  has a front side and a rear side. The exhaust gas outlet  17  which extends in an outlet direction  31 , which is advantageously parallel to the axis  19 , is disposed on the front side. The turbine wheel  3  (not illustrated in  FIG.  3   ) is received in the central region  21 , the exhaust gas outlet  17  extending across the latter, such that the turbine wheel  3  is rotatable about the axis  19 . The exhaust gas flows away from the turbine wheel  3  in the outlet direction  31 . 
     A connection device  33 , which is configured for connecting the turbine housing  9  to a bearing housing  7  (not illustrated in  FIG.  3   ) is provided on the rear side, the latter facing away from the exhaust gas outlet  17 . The connection device  33  has an encircling flange and is configured such that the connection device  33  by means of a clamp with a V-profile is connectable to the bearing housing  7 . 
     The exhaust gas routing  25 , which is defined by the internal wall  35  of the turbine housing  9 , in the shape of a spiral runs about the central region  21 . The exhaust gas routing  25  comprises the volute  13  and the volute outlet gap  29  which from the volute  13  extends radially to the central region  21  and is configured such that the exhaust gas, which is guided about the turbine wheel  3  by the volute  13 , can flow from the volute  13  onto the turbine wheel  3 . 
     The section in  FIG.  3    shows two opposite regions of the volute  13  of dissimilar sizes, because the cross-sectional area of the volute  13  decreases as the encirclement increases. 
     The volute  13  comprises a portion  45  which encircles the axis  19  and has a convexity  37 . The convexity  37  of the internal wall  35 , counter to the outlet direction  31 , extends beyond the volute outlet gap  29 . A depth by way of which the convexity  37  extends beyond the volute outlet gap  29  decreases as the encirclement increases, until the depth vanishes entirely. This may be the case after approx. 200°±15°, for example. Moreover, the volute  13  in the portion  45  is flattened in such a manner that a volute contour in sectional faces through which the axis  19  runs has a straight linear portion  39 . The straight linear portion  39  runs from the convexity  37  at an angle to the axis  19  such that the straight linear portion  39  is inclined in relation to the exhaust gas outlet  17 . In other words, the straight linear portion  39  conjointly with the axis  19  defines an angle facing the exhaust gas outlet  17  that is less than or equal to 90°. The volute contour is the profile of the internal wall  35  that defines the volute  13  in the sectional plane. A length  41  of the straight linear portion  39  decreases as the encirclement of the volute  13  increases, until the straight linear portion  37  vanishes entirely. The same applies to the flattened region which is formed by the straight linear portions  37  and which tapers as the encirclement of the volute  13  increases. In both cases, this may be after approx. 200°±15°. The convexity  37  and the flattened region do not necessarily have to vanish at the same location. 
     As a result of the convexity  37  of the volute  13  in the direction of the bearing housing  7 , the thermally induced stress during repeated heating and cooling is also reduced such that the thermomechanical fatigue and thus the tendency toward cracking is reduced. 
       FIG.  4    shows a section through the beginning of the exhaust gas routing  25  for an exemplary embodiment, wherein the axis  19  runs through the sectional plane. The exhaust gas outlet  17  is not illustrated for the sake of clarity. The sectional plane is directly behind the exhaust gas inlet  23 . 
     The exhaust gas routing  25  can be defined by means of various parameters. A is the spacing between the rear side and the volute outlet gap  29 , more specifically the rear side of the latter. The spacing A is defined between lines that are perpendicular to the axis  19 . The spacing A is the width on the rear side of the turbine housing contour. B is the width of the fastening device  33  for the clamp with the V-profile and comprises the flange that is encompassed by the clamp. C is the wall thickness without the fastening device  33 . The afore-mentioned parameters are pre-defined substantially by the frame size of the exhaust turbocharger. 
     Further parameters are D as the width of the elevation between the rear side of the volute outlet gap  29  and the apex of the convexity  37 , and the angle τ between the line perpendicular to the axis  19  at the apex of the convexity  37  and the straight portion  39 . D is the depth by way of which the convexity  37  protrudes beyond the volute outlet gap  29 . D and τ can be optimized so as to influence the flow-directing properties of the volute  13 . The regions beyond the volute outlet gap  29  and the straight linear portions  39  are advantageously radiused. In one exemplary embodiment the parameters are as follows: A is 16.3 mm±0.3 mm, B is 8 mm, C is at least 4 mm, and variable D is at most 4 mm. In another exemplary embodiment the parameters are as follows: A is 20.2 mm±0.3 mm, B is 10 mm, C is at least 4 mm, and variable D is at most 4.5 mm. 
     The convexity  39  arises in a portion  45  which encircles the axis  19  and in an arcuate manner extends between the beginning of the exhaust gas routing  25  and an end. The beginning and the end between the axis  19  define an angle of approx. 200°±15°. The length of the straight linear portion  37  decreases as the encirclement of the axis  19  increases. Likewise, the depth, i.e. D, by way of which the convexity  37  extends beyond the volute outlet gap  29 , decreases as the encirclement of the axis  19  increases. The flattened region having the straight linear portions  39  is on the rear side of the volute outlet gap  29 , i.e. at least partially to the rear of a line  43  which along a volute outlet gap contour on the rear side runs perpendicularly to the axis  19 , the parameters A and D also extending up to the line  43 . In an alternative embodiment, the flattened region may also extend beyond the volute outlet gap  29 , specifically to the rear of a line which along a volute outlet gap contour on the front side runs perpendicularly to the axis  19 . The exhaust gas routing  25  runs up to the tongue  27 , wherein the volute contour in a sectional face on the tongue end region, through which the axis  19  runs, no longer has a straight linear region  39  and the convexity  37  has also vanished such that the volute contour extends away from the volute outlet gap  29  in a straight manner. 
       FIG.  5    schematically visualizes the difference between an exemplary embodiment of a volute  13  according to the invention and a conventional B-type volute  12 ′ without a convexity  37 . Volute contours of the internal wall  35 ,  35 ′ for the exemplary embodiment according to the invention are illustrated as solid lines and for the conventional exemplary embodiment as dashed lines, respectively. The outer solid line visualizes the wall thickness of the exemplary embodiment according to the invention. While the two exemplary embodiments in terms of the cross-sectional area thereof have only minor differences, the radial extent relative to the axis  19  of the exemplary embodiment according to the invention is smaller, since the conventional exemplary embodiment with the identical wall thickness would extend further in the radial direction because the volute  13 ′ of the conventional exemplary embodiment also extends further in the radial direction. Moreover, a radius of the center of gravity of the exemplary embodiment according to the invention, by virtue of the convexity  37 , is closer to the axis  19 , this being associated with an improved performance. 
       FIG.  6    schematically shows a section through the exhaust gas routing  25 ,  25 ′, perpendicular to the axis  19 , of an exemplary embodiment according to the invention and of a conventional exemplary embodiment with the same performance. The exemplary embodiment of the exhaust gas routing  25  according to the invention is illustrated by solid lines, while the conventional exemplary embodiment of the exhaust gas routing  25 ′ is illustrated by dashed lines. The radial extent along the entire volute profile is smaller in the case of the exemplary embodiment according to the invention. 
     Moreover schematically visualized in  FIG.  6    is an exemplary extent of the portion  45  which encircles the axis and has the convexity  37  and the straight linear portions  39 , between the beginning of the portion  45  at the beginning of the exhaust gas routing and at the end of the portion  45  after approx. 200°. 
     The smaller extent in the radial direction is associated with a smaller installation size and a lower weight of the turbine housing  9  according to the invention. This also leads to less material being required for the turbine housing  9 . Nevertheless, the turbine housing  9  according to the invention can adhere to pre-defined dimensions and be produced in the same way as a convention turbine housing, and at the same time still have a smaller installation size with an identical or improved performance. Typical values for the material savings for a turbine wheel  3  of 45 mm are 100 g in saved materials, and 450 g in saved materials for a turbine wheel of 67 mm. Depending on the material used and the turbine size, material savings of approximately 60 g to 450 g are thus possible. This is also associated with cost savings. 
     The features which are set forth above and in the claims, and which can be derived from the illustrations, can be advantageously implemented individually as well as in various combinations. The invention is not limited to the exemplary embodiments described but may be modified in many ways within the scope of the ability of a person skilled in the art. 
     LIST OF REFERENCE SIGNS 
     
         
           1  Shaft 
           3  Turbine wheel 
           5  Compressor wheel 
           7  Bearing housing 
           9  Turbine housing 
           11  Compressor housing 
           13 ,  15  Volute 
           17  Exhaust gas outlet 
           19  Axis 
           21  Central region 
           23  Exhaust gas inlet 
           25  Exhaust gas routing 
           27  Tongue 
           29  Volute outlet gap 
           31  Outlet direction 
           33  Connection device 
           35  Internal wall 
           37  Convexity 
           39  Linear portion 
           41  Length 
           43  Line 
           45  Portion 
         A, B, C, D, τ Parameter