Impeller for an exhaust gas turbocharger

Abstract

An impeller for an exhaust gas turbocharger may include a hub main body and blades arranged thereon. The hub main body may be configured as a polygon with a number of segments that may be tilted with respect to one another, the number of the segments corresponding to a number of the blades. Alternatively, the hub main body may have a main surface that faces the blades and undulates in a circumferential direction, a number of the undulations corresponding to the number of the blades.

Claims

1. An impeller for an exhaust gas turbocharger, comprising: a hub main body and blades arranged thereon; wherein the hub main body is configured as a polygon with a number of segments that are tilted with respect to one another in relation to a circumferential direction, the number of the segments corresponding to a number of the blades; and wherein each of the number of segments extends and increases in thickness from one blade to an adjacent blade in a rotation direction of the impeller and has a main surface with a straight contour, a thick side of each of the number of segments merging into a thin side of an adjacent segment to form a sawtooth configuration of a hub surface.

2. The impeller according to claim 1, wherein a transition from a segment into an associated blade is rounded.

3. The impeller according to claim 2, wherein the rounded transition is formed by way of a material addition to the main surface of the respective segment.

4. The impeller according to claim 1, wherein the hub main body has a back that undulates in the circumferential direction.

5. An exhaust gas turbocharger comprising an impeller having a hub main body and blades arranged thereon; wherein the hub main body is configured as a polygon with a number of segments that are tilted with respect to one another in relation to a circumferential direction, the number of the segments corresponding to a number of the blades; and wherein each of the number of segments extends and increases in thickness from one blade to an adjacent blade in a rotation direction of the impeller and has a main surface with a straight contour, a thick side of each of the number of segments merging into a thin side of an adjacent segment to form a sawtooth configuration of a hub surface.

6. The exhaust gas turbocharger according to claim 5, wherein a transition from a segment into an associated blade is rounded.

7. The exhaust gas turbocharger according to claim 6, wherein the rounded transition is formed by way of a material addition to the main surface of the respective segment.

8. The impeller according to claim 1, wherein at least a subset of the segments are tilted to a different extent with respect to at least one of the hub main body, the respective blade, and one another.

9. The exhaust gas turbocharger according to claim 5, wherein at least a subset of the segments are tilted to a different extent with respect to at least one of the hub main body, the respective blade, and one another.

10. The exhaust gas turbocharger according to claim 5, wherein each segment decreases in thickness from one radial end toward an adjacent segment to form a sawtooth configuration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings, in each case diagrammatically:

(2) FIG. 1 shows a view of a hub main body of an impeller according to the invention in accordance with a first embodiment,

(3) FIG. 2 shows a side view of an impeller according to the invention in accordance with the first embodiment,

(4) FIG. 3 shows a side view of an impeller according to the invention in accordance with a second embodiment,

(5) FIG. 4 shows a cross section through an impeller according to the invention in accordance with a variant of the second embodiment, and

(6) FIG. 5 shows a side view of an impeller in accordance with FIG. 4.

DETAILED DESCRIPTION

(7) According to FIGS. 1-5, an impeller 1 according to the invention for an exhaust gas turbocharger 2 has a hub main body 3 and blades 4 which are arranged thereon. FIG. 1 shows merely the hub main body 3, but not the associated blades 4. In order for it then to be possible to optimize the impeller 1 according to the invention with regard to a stress which occurs in the region of a transition 7 between the respective blade 4 and the hub main body 3, two alternative embodiments of the hub main body 3 are provided, a first alternative being shown in FIGS. 1 and 2 and the second alternative being shown in FIGS. 3 to 5.

(8) According to FIGS. 1 and 2, the hub main body 3 is configured here according to the invention as a polygon with a number of segments 5 which are tilted with respect to one another, which number corresponds to the number of blades 4. Here, the individual segments 5 (cf. also FIG. 2) preferably have a main surface 6 of straight cross section at least radially on the outside, which segments 5, depending on requirements, can be tilted to a different extent with respect to the hub main body 3 or the respective blade 4 and also with respect to one another. Here, the transition 7 from a segment 5 into an associated blade 4 is preferably rounded, the rounded portion or the rounded transition 7 being formed by way of a material addition 8, that is to say an additional material application, to the main surface 6 of the respective segment 5.

(9) In comparison to hub main bodies which are known from the prior art and in which they had been configured exclusively as a round rotational body, the hub main body 3 according to the invention and therefore also the impeller 1 according to the invention affords the great advantage that the said impeller 1 is reinforced exclusively locally in that region, in which the stresses which occur during operation of the exhaust gas turbocharger 2 are the highest. Moreover, a notch-free transition both into the main surface 6 of the segment 5 and into the associated blade 4 can be achieved by way of the rounded portion, as a result of which stress peaks can be avoided.

(10) If the impeller 1 according to the invention in accordance with the second alternative embodiment in FIG. 3 is considered, it can be seen that the hub main body 3 here has a main surface 6 which faces the blades and undulates in the circumferential direction, a number of the individual undulations 10 corresponding to a number of the blades 4. In addition, in this case, a back of the main surface 6 or the hub main body 3 is also of undulating configuration, the undulations 10 of the back 9 and the main surface 6 running in parallel. It goes without saying that the back 9 can also be configured here without undulations of this type, that is to say can be of straight configuration, it also being possible in this context for the back 9 on the hub main body 3 of the impeller 1 according to FIGS. 1 and 2 to be of straight configuration or else configured with undulations 10. Here, a transition 7 from the main surface 6 into an associated blade 4 is preferably arranged in the region of an undulation peak 11 or at least slightly next to it. It can be provided, moreover, that a transition 7 between the undulating main surface 6 and the associated blade 4 is rounded, as shown according to FIG. 3 by way of an interrupted line, a rounded transition 7 of this type merging into the main surface 6 by way of a tangent which is applied to an undulation slope 12. In a similar way, a tangential transition into the associated blade 4 can also be achieved.

(11) In both embodiments which are shown and are alternative but nevertheless are equivalent in relation to the stress and weight optimization, a common feature here is that they are capable of absorbing, in particular, the high stresses which occur in the region of a transition 7 from a main surface 6 of the hub main body 3 into the associated blade 4 in an improved manner by way of a special configuration or dimensional change of the hub main body 3, which has previously not existed, and of ensuring a longer service life as a result. In comparison with hub main bodies which are thickened completely, that is to say at all locations, it goes without saying that a hub main body 3 of this type according to the invention which is reinforced merely locally is considerably lighter and, as a result, has a reduced mass moment of inertia, as a result of which an exhaust gas turbocharger 2 which is equipped with the said impeller 1 exhibits an improved response behaviour.

(12) In the conventional manner, it is the case here that all of the embodiments as per FIGS. 3 to 5 have in common the fact that the undulation peaks 11 are arranged in each case between two blades 4.

(13) Considering the impeller 1 as per FIG. 4, it can be seen that the undulation peaks 11 taper off in a radially inward and/or radially outward direction and transition into the main surface 6, such that no undulation peaks 11 are present at an impeller inlet 13 and at an impeller outlet 14. Here, in FIG. 4, the original profile of an impeller according to the prior art is shown by way of a solid line, whereas the profile of the impeller 1 according to the invention in the region of the undulation peak 11 is shown by a dotted line. In the case of an impeller 1 as per FIGS. 4 and 5, the hub main body 3 has a planar back 9.

(14) Here, the radial position of the undulation peaks 11 may be formed, in relation to the impeller size (impeller radius), from the quotient impeller radius/undulation peak position. Here, it has been found that the ratio of the undulation peak 11 to the radius RVR of the impeller 1 lies between 1.1 and 2.2. For a ratio of a radius RVR of the impeller 1 to a maximum radial extent RWB of the undulation peak 11, the following therefore applies:

(15) 1.1<RVR/RWB<2.2.

(16) The thickening, in particular additional material portions 8, of the undulation peaks 11 is thus present only in the intermediate region between two adjacent blades 4. The appearance of the profile changes depending on where the most highly loaded region is. However, all of the profiles have in common the fact that they are rotationally asymmetrical and return to the original, rotationally symmetrical hub profile again both in the direction of the impeller inlet 13 and in the direction of the impeller outlet 14. In this way, thermodynamic disadvantages can be avoided.