Exhaust gas turbocharger
The invention relates to an exhaust gas turbocharger with a manifold-flow casing, in particular a dual-flow casing ( 47 ) and a turbine wheel ( 34 ) which is rotatably arranged within said manifold-flow casing, onto which an exhaust gas flow ( 14; 16 ) may be led via at least one of several flow channels ( 18, 26 ), and an outlet opening ( 78; 80 ) following said one flow channel ( 18, 26 ) and covering an angle of 180° max. about an axis of rotation ( 44 ) of the turbine wheel ( 34 ), so that a shaft ( 38 ) is rotating which is arranged coaxially and non-rotationally relative to the turbine wheel ( 34 ), which is supported in a shaft bearing ( 42 ).
1. An exhaust gas turbocharger with a manifold dual-flow casing ( 47 ) and a turbine wheel ( 34 ) which is rotatably arranged within said manifold dual-flow casing ( 47 ), onto which an exhaust gas flow ( 14 ; 16 ) is led via at least two flow channels ( 18 , 26 ), and at least two outlet openings ( 78 , 80 ) respectively following each of said at least two flow channels ( 18 , 26 ) and each of said at least two outlet openings ( 78 , 80 ) covering an angle of 180° maximum about an axis of rotation ( 44 ) of the turbine wheel ( 34 ), so that a shaft ( 38 ) having a circular cross-section is rotatably arranged coaxially and non-rotationally relative to the turbine wheel ( 34 ), the shaft ( 38 ) is supported in a shaft bearing ( 42 ),
characterized in that
the shaft bearing ( 42 ) has an inner circumferential surface having a non-circular shape extending in surrounding coaxial relationship with the shaft ( 38 ), the non-circular inner circumferential surface has a cross-sectional curvature which varies in a circumferential direction, the shaft bearing ( 42 ) is a multi-surface radial plain bearing with the non-circular inner circumferential surface comprising a number of discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) which number is either equal to the number of the flow channels ( 18 , 26 ) or an integer multiple of the number of the flow channels ( 18 , 26 ), wherein the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) are oriented relative to the least two outlet openings ( 78 , 80 ).
2. The exhaust gas turbocharger according to claim 1 ,
characterized in that the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) are formed consistent with respect to the shape and a distance to a shaft bearing center axis ( 46 ).
3. The exhaust gas turbocharger according to claim 1 ,
characterized in that
the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) of the multi-surface radial plain shaft bearing ( 42 ) are further defined in their circumferential position about a shaft bearing center axis ( 46 ) relative to a bearing housing ( 28 ) which is non-rotationally connected or integral with the manifold-flow casing, wherein at least one of the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) is arranged such that a radial force, which acts on the shaft ( 38 ) due to a one-sided application of the exhaust gas flow, is supported at the least one of the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) in a direction in which the multi-surface radial plain shaft bearing ( 42 ) exhibits a maximum bearing stiffness.
4. The exhaust gas turbocharger according to claim 3 ,
characterized in that
the at least two outlet openings ( 78 , 80 ) of the at least two flow channels ( 18 , 26 ) each cover an angle ( 82 ) which is less than 180° and that the non-circular inner circumferential surface of the multi-surface radial plain shaft bearing ( 42 ) has four discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ), the cross-sectional curvature of the non-circular inner circumferential surface of the multi-surface radial plain shaft bearing ( 42 ) having a first of two largest inner diameters lying along a first plane ( 93 ) passing through the shaft bearing center axis ( 46 ) and having a second of two largest inner diameters lying along a second plane ( 94 ) passing through the shaft bearing center axis ( 46 ), the first plane ( 93 ) and the second plane ( 94 ) intersect at an interface ( 92 ) between the two outlet openings ( 78 , 80 ) under an angle of intersection of about 45° with the shaft bearing center axis ( 46 ).
5. The exhaust gas turbocharger according to claim 1 ,
characterized in that
the multi-surface radial plain shaft bearing ( 42 ) comprises a bearing sleeve ( 53 ) which is non-rotationally defined relative to the bearing housing ( 28 ).
6. The exhaust gas turbocharger according to claim 1 ,
characterized in that
the multi-surface radial plain shaft bearing ( 42 ) further comprises several lubricant pockets ( 62 , 64 , 66 , 68 ), each of the lubricant pockets ( 62 , 64 , 66 , 68 ) formed proximate a juncture of each pair of discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ), each of the lubricant pockets ( 62 , 64 , 66 , 68 ) extend in parallel relationship to the shaft bearing center axis ( 46 ) and each of the lubricant pockets ( 62 , 64 , 66 , 68 ) leads into a respective radial recess ( 58 ; 59 ; 60 ; 61 ) which is in permanent alignment with a respective lubricant supply duct ( 54 ; 55 ; 56 ; 57 ) in the bearing housing ( 28 ) when the shaft ( 38 ) is rotating.
7. The exhaust gas turbocharger according to claim 3 ,
characterized in that
the discrete adjoining bearing surfaces ( 70 , 72 , 74 , 76 ) of the multi-surface radial plain shaft bearing ( 42 ) are directly integrated into the bearing housing ( 28 ).