EP3601739B1 - Turbocharger for an internal combustion engine, and turbine wheel - Google Patents

Description

The invention relates to a turbocharger for an internal combustion engine.

Exhaust gas turbochargers are increasingly being used to increase the performance of motor vehicle internal combustion engines. This is happening more and more frequently with the aim of reducing the size and weight of the internal combustion engine with the same or even increased performance and at the same time reducing consumption and thus CO ₂ emissions in view of the increasingly strict legal requirements in this regard. The operating principle consists in using the energy contained in the exhaust gas flow in order to increase a pressure in an intake tract of the internal combustion engine and thus bring about better filling of a combustion chamber of the internal combustion engine with air-oxygen. This means that more fuel, such as petrol or diesel, can be converted per combustion process, i.e. the performance of the combustion engine can be increased.

For this purpose, the exhaust gas turbocharger has an exhaust gas turbine arranged in the exhaust tract of the internal combustion engine, a fresh air compressor arranged in the intake tract and a rotor bearing arranged in between. The exhaust gas turbine has a turbine housing and a turbine impeller which is arranged therein and is driven by the exhaust gas mass flow. The fresh air compressor has a compressor housing and a compressor impeller which is arranged therein and builds up boost pressure. The turbine impeller and the compressor impeller are arranged in a rotationally fixed manner on the opposite ends of a common shaft, the so-called rotor shaft, and thus form the so-called turbocharger rotor. The rotor shaft extends axially between the turbine rotor and the compressor rotor through the rotor bearing arranged between the exhaust gas turbine and the fresh air compressor and is rotatably mounted in it radially and axially with respect to the rotor shaft axis. According to this structure the turbine impeller driven by the exhaust gas mass flow drives the compressor impeller via the rotor shaft, which increases the pressure in the intake tract of the combustion engine, based on the fresh air mass flow behind the fresh air compressor, and thus causes better filling of the combustion chamber with air-oxygen.

Such an exhaust gas turbocharger for an internal combustion engine is, for example, in document EP 3 144 541 A1 disclosed. This has a bearing housing which is arranged between an exhaust gas turbine with a turbine impeller and a centrifugal compressor with a compressor impeller and in which a rotor shaft is mounted so that it can rotate about a rotor axis of rotation on which the turbine impeller and the compressor impeller are each arranged in a rotationally fixed manner. The turbine wheel has wheel blading and is arranged in the turbine housing, which is mechanically fixed to the bearing housing. The turbine wheel includes turbine blades each having a flow leading edge and a flow trailing edge that define an entry radius and an exit radius of the turbine wheel. The turbine blades have an outer contour facing the turbine housing, which extends from the flow inlet edge to the flow outlet edge. The turbine housing has a housing contour that is opposite the outer contour of the turbine blades, with a radial distance being formed between the housing contour and the outer contour, which enables contact-free rotation of the turbine impeller in the turbine housing.

Furthermore, the publication also discloses U.S. 2016 341 072 A1 a turbocharger with an exhaust gas turbine having a turbine wheel arranged in a turbine housing with a housing contour as already described in the previous paragraph.

An object on which the invention is based is to specify a concept for a turbocharger that contributes to safe operation of a turbocharger.

• Zumindest eine Turbinenschaufel des Turbinenrads weist eine Strömungseintrittskante und eine Strömungsaustrittskante für den Abgasmassenstrom auf.
• Die Strömungseintrittskante weist einen maximalen Eintrittsradius R_in auf und die Strömungsaustrittskante weist einen maximalen Austrittsradius R_out auf, jeweils bezogen auf die Läuferdrehachse.
• Die zumindest eine Turbinenschaufel weist eine dem Turbinengehäuse zugewandte Außenkontur auf, die sich von der Strömungseintrittskante bis zu der Strömungsaustrittskante erstreckt und eine axiale Erstreckungslänge L_axTip hat.
• Das Turbinengehäuse weist eine Gehäusekontur auf, die der Außenkontur gegenüberliegt.
• Die Außenkontur der zumindest einen Turbinenschaufel weist einen axialen Längenanteil L_cover der axialen Erstreckung L_axTip auf, in welchem ein Durchmesser des Turbinenrads größer ist als ein kleinster Durchmesser DA des Turbinengehäuses am Turbinenschaufelaustritt für den Abgasmassenstrom AM.
• Zwischen der Gehäusekontur und der Außenkontur ist bezüglich der Läuferdrehachse ein geringster radialer Abstand Tip_clr ausgebildet.

A turbocharger for an internal combustion engine according to claim 1 is disclosed. The turbocharger has a bearing housing in which a rotor shaft is mounted so that it can rotate about a rotor axis of rotation, the rotor shaft being mounted in the bearing housing via at least two radial bearings. The turbocharger has an exhaust gas turbine with a turbine wheel which is arranged in a torque-proof manner on the rotor shaft and which has impeller blading with a plurality of turbine blades, and with a turbine housing which is mechanically fixed to the bearing housing and which surrounds the turbine wheel. With regard to a meridional view of the exhaust gas turbine, the following applies:

• At least one turbine blade of the turbine wheel has a flow inlet edge and a flow outlet edge for the exhaust gas mass flow.
• The flow inlet edge has a maximum inlet radius R _in and the flow outlet edge has a maximum outlet radius R _out , each based on the rotor axis of rotation.
• The at least one turbine blade has an outer contour facing the turbine housing, which extends from the flow inlet edge to the flow outlet edge and has an axial extension length L _axTip .
• The turbine housing has a housing contour that is opposite to the outer contour.
• The outer contour of the at least one turbine blade has an axial length portion L _cover of the axial extension L _axTip , in which a diameter of the turbine wheel is larger than a smallest diameter DA of the turbine housing at the turbine blade outlet for the exhaust gas mass flow AM.
• A smallest radial distance Tip _{clr is} formed between the housing contour and the outer contour with respect to the rotor axis of rotation.

The turbine housing and the turbine wheel are designed and matched to one another in such a way that the following condition or equation is met: $$\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}.$$

It was recognized that damage to the turbocharger can occur during operation of the turbocharger, for example during test bench runs for the design of the turbocharger or components of the turbocharger such as the rotor. For example, a component failure of the rotor shaft or the impellers, such as a broken shaft, can occur.

If the rotor shaft breaks, for example, the turbine wheel can no longer be held in its intended position axially by an axial bearing. In this case, the turbine wheel would be moved in the direction of a turbine housing outlet for the exhaust gas mass flow primarily by aerodynamic forces, for example due to prevailing gas pressures. The portion of the turbine blades of the turbine wheel that has a larger diameter than an outlet diameter of the turbine housing at the downstream end of the turbine wheel abuts the turbine housing and hinders the turbine wheel in its axial movement in the direction of the turbine housing outlet. It was also recognized that if this proportion of the turbine wheel blades is not sufficiently large, the turbine blades are plastically deformed in the event of a shaft breakage in such a way that the turbine wheel can carry out a further, unwanted axial displacement.

A disadvantage in such a case would be, among other things, that piston rings of oil seals could leave their original axial position and a sealing effect would be lost. This would have the negative consequence, among other things, that oil could escape in such quantities that the combustion engine, in whose oil circuit the turbocharger is coupled, would have to be switched off immediately in order to avoid damage. However, an oil leak should be avoided at all costs or as far as possible in order to at least guarantee the emergency running properties of the system. In addition, it was recognized that a broken shaft between the oil seals, such as the piston rings of both seals, is disadvantageous because, in addition to the impellers and the shaft stubs remaining on them, the seals could also leave the turbocharger, which would further promote the negative oil loss described.

The turbocharger described provides that the turbine wheel and turbine housing are designed and arranged according to the condition (equation) formulated above. The condition stipulates that a contour profile of the turbine housing and/or the at least one turbine wheel blade are specifically redesigned compared to known turbines. In particular, a length portion (L _cover ) of the turbine wheel blade, in which a diameter of the turbine wheel is larger than a smallest diameter DA of the turbine housing at the turbine blade outlet, is increased in such a way that in the event of a shaft breakage, a larger proportion of the turbine wheel blades would be plastically deformed in the event of an axial displacement , so that further axial movement of the turbine wheel with respect to the rotor axis of rotation is impeded or limited. For example, starting from a conventional housing contour in the area of the turbine wheel, the length portion of the turbine wheel blade in which a diameter of the turbine wheel is larger than a smallest diameter DA of the turbine housing at the turbine blade outlet is increased simply by the redesign. In other words, the condition defines a minimum value of said length portion of the turbine wheel blade.

Such a design based on the given equation contributes to the fact that the turbine wheel, after a shaft breakage, i.e. in the event of damage to the turbocharger, one provides greater resistance to further axial displacement upon collision with the housing. The equation thus enables an optimal design for the turbine wheel and turbine housing on the basis of various parameters. Depending on the framework conditions for the turbocharger, such as application, intended use or others, certain parameters of the like can be specified, with one or more remaining parameters being able to be determined using the equation. In this way, a reasonable adjustment of the parameters can always be achieved according to the framework conditions. In particular, using the equation, it is possible to easily determine the axial cover length L _cover necessary for the above advantages and functions.

A turbocharger designed according to the conditions helps to avoid the disadvantages mentioned at the outset in the event of damage, in particular the shaft breakage mentioned, in particular when the turbine wheel is only mounted radially. In this case, it is not absolutely necessary to constructively reinforce a back disk and/or the turbine wheel blades. In other words, thanks to the above condition, it is not necessary to correspondingly thicken the turbine wheel blades. Also, thanks to the above condition, it is not necessary to provide a low trim ratio, ie a ratio between the maximum exit radius R _out and the maximum entry radius R _in . Material costs, among other things, can be saved as a result. Both such measures would be disadvantageous with regard to the performance of the turbocharger, for example due to higher mass inertia.

A meridional view means, for example, a flat, two-dimensional view in which an outermost contour of the turbine wheel is shown, which the turbine wheel traces during a rotation about the rotor axis of rotation, which also corresponds to an axis of rotation of the turbine wheel. The view can also relate to or include at least parts of the turbine housing, with an inner contour with a minimal radius in relation to the axis of rotation in the area of the turbine wheel being shown in particular, which the turbine housing would traverse when rotating about the axis of rotation.

The housing contour of the turbine housing (English: shroud) opposite the outer contour is designed to correspond to the outer contour. The smallest radial distance Tip _clr with respect to the axis of rotation of the rotor can be a distance that is constant over the entire axial area between the leading edge and the trailing edge. However, it is also conceivable for the distance to be present only in sections, in a single area or point with respect to the axis of rotation.

The axial length component (L _cover ) means that axial extent of the outer contour in which a radius or a diameter of the turbine wheel with respect to the rotor axis of rotation is larger than a minimum diameter/radius of the turbine housing in the region of a downstream end of the turbine wheel. In other words, in this area the diameter of the turbine wheel is larger than a smallest diameter of the turbine housing. In other words, it is that axial area of a turbine wheel which, if the turbine wheel and the turbine housing were projected into a plane normal to the rotor axis of rotation, is covered or overlapped by the turbine housing. In other words, this is the area that lies in the shadow of the turbine housing in relation to the rotor axis of rotation. In other words, the outer contour of the at least one blade has an axial overlap section that corresponds to the axial length component L _cover of the axial extension L _axTip .

The following embodiments all contribute to the above advantages and functions, with the above condition being advantageously further developed by specifying one or more limit values.

.According to one embodiment, the ratio Tip _clr to R _{in is} : $\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\le 2.5\%$

.

.According to one embodiment, the ratio Tip _clr to R _{in is} : $\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\le 2.0\%$

.

.According to one embodiment, the ratio Tip _clr to R _{in is} : $\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\le 1.5\%$

.

.According to one embodiment, the ratio of L _cover to L _{axtip is} : $\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>0.2$

.

.According to one embodiment, the ratio of L _cover to L _{axtip is} : $\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>0.25$

.

.According to one embodiment, the ratio of L _cover to L _{axtip is:} $\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>0.3$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}>0.8$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.95$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.93$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.92$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.91$

.

.According to one embodiment, the ratio of R _out to R _{in is} : $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.90$

.

The ratio R _out to R _in is also referred to as the trim or trim ratio.

According to embodiments, the trim ratio is between 0.8 and one of the other limits specified above.

Furthermore, a turbine wheel for a turbocharger according to one of the previous embodiments is disclosed. The turbine wheel has impeller blading with a plurality of turbine blades. The turbine wheel is designed in such a way that the following condition is met: $$\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}$$

• zumindest eine Turbinenschaufel des Turbinenrads eine Strömungseintrittskante und eine Strömungsaustrittskante für den Abgasmassenstrom aufweist;
• R_in einen maximalen Eintrittsradius der Strömungseintrittskante und R_out einen maximalen Austrittsradius der Strömungsaustrittskante beschreibt, jeweils bezogen auf eine Drehachse des Turbinenrads;
• L_axTip eine axiale Erstreckungslänge einer Außenkontur der zumindest einen Turbinenschaufel beschreibt, wobei sich die Außenkontur von der Strömungseintrittskante bis zu der Strömungsaustrittskante erstreckt und in einem bestimmungsgemäßen Betrieb einem umgebenden Turbinengehäuse zugewandt ist;
• L_cover einen axialen Längenanteil der axialen Erstreckung L_axTip der Außenkontur beschreibt, in welchem ein Durchmesser des Turbinenrads größer ist als ein kleinster Durchmesser DA des Turbinengehäuses am Turbinenschaufelaustritt;
• Tip_clr einen geringsten radialen Abstand zwischen einer Gehäusekontur des Turbinengehäuses, welche in dem bestimmungsgemäßen Betrieb der Außenkontur gegenüberliegt, und der Außenkontur bezüglich der Läuferdrehachse beschreibt.

With regard to a meridional view of the turbine wheel, it applies that

• at least one turbine blade of the turbine wheel has a flow inlet edge and a flow outlet edge for the exhaust gas mass flow;
• R _in describes a maximum inlet radius of the flow inlet edge and R _out describes a maximum outlet radius of the flow outlet edge, in each case based on an axis of rotation of the turbine wheel;
• L _{axTip describes} an axial extension length of an outer contour of the at least one turbine blade, the outer contour extending from the flow inlet edge to the flow outlet edge and facing a surrounding turbine housing in normal operation;
• L _cover describes an axial length component of the axial extension L _axTip of the outer contour, in which a diameter of the turbine wheel is larger than a smallest diameter DA of the turbine housing at the turbine blade outlet;
• Tip _{clr describes} a smallest radial distance between a housing contour of the turbine housing, which is opposite the outer contour in normal operation, and the outer contour with respect to the rotor axis of rotation.

The above statements apply analogously.

The turbine wheel enables the advantages and functions mentioned above.

• Ermitteln und/oder Bestimmen der Parameter des maximalen Eintrittsradius R_in, des maximalen Austrittsradius R_out, der axialen Erstreckungslänge L_axTip, des axialen Längenanteils L_cover und des geringsten radialen Abstands Tip_clr derart, dass für das Turbinenrad und das Turbinengehäuse die folgende Bedingung erfüllt ist: $$\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}$$
  
  und
• Fertigen des Turbinenrads und des Turbinengehäuses anhand der mittels der Bedingung ermittelten Parameter.

Furthermore, a method for manufacturing a turbocharger according to one of the above embodiments is disclosed. The procedure includes the steps:

• Determine and/or determine the parameters of the maximum entry radius R _in , the maximum exit radius R _out , the axial extension length L _axTip , the axial length portion L _cover and the smallest radial distance Tip _clr such that the following condition is met for the turbine wheel and the turbine housing is: $$\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}$$
  
  and
• Manufacture of the turbine wheel and the turbine housing based on the parameters determined using the condition.

The above statements apply analogously.

The method enables the advantages and functions mentioned above.

Exemplary embodiments of the invention are described below without restricting the generality.

The exemplary embodiments are described below with the aid of the attached figures. Elements that are of the same type or have the same effect are provided with the same reference symbols across the figures.

Figur 1

eine schematische Schnittansicht eines Turboladers,

Figur 2 und 3

zwei schematische Schnittansichten von Abgasturbinen eines Turboladers,

Figur 4

eine schematische Schnittansicht einer Abgasturbine eines Turboladers gemäß einem Ausführungsbeispiel,

Figur 5

eine Gleichung für die Auslegung der Abgasturbine gemäß der vorliegenden Erfindung und

Figur 6

eine Diagrammdarstellung der Gleichung der Figur 5 mit drei beispielhaften Parameterauswahlen.

In the figures show:

figure 1

a schematic sectional view of a turbocharger,

Figure 2 and 3

two schematic sectional views of exhaust gas turbines of a turbocharger,

figure 4

a schematic sectional view of an exhaust gas turbine of a turbocharger according to an embodiment,

figure 5

an equation for the design of the exhaust gas turbine according to the present invention and

figure 6

a diagram representation of the equation of the figure 5 with three exemplary parameter selections.

figure 1 shows a schematic of an exemplary exhaust gas turbocharger 1 in a sectional view, which has an exhaust gas turbine 20 , a fresh air compressor 30 and a rotor bearing 40 . The exhaust gas turbine 20 is equipped with a wastegate valve 29 and an exhaust gas mass flow AM is indicated with arrows. The fresh air compressor 30 has an overrun air recirculation valve 39 and a fresh air mass flow FM is also indicated with arrows. A so-called turbocharger rotor 10 of the exhaust gas turbocharger 1 has a turbine wheel 12 (also called turbine wheel), a compressor wheel 13 (also called compressor wheel) and a rotor shaft 14 (also called shaft). During operation, the turbocharger rotor 10 rotates about a rotor axis of rotation 15 of the rotor shaft 14. The rotor axis of rotation 15 and at the same time the turbocharger axis 2 (also referred to as the longitudinal axis) are represented by the center line drawn in and characterize the axial alignment of the exhaust gas turbocharger 1.

As a rule, a common exhaust gas turbocharger 1, as shown in figure 1 shown, a multi-part structure. A turbine housing 21 that can be arranged in the exhaust tract of the internal combustion engine, a compressor housing 31 that can be arranged in the intake tract of the internal combustion engine, and a bearing housing 41 between the turbine housing 21 and the compressor housing 31 are arranged next to one another with respect to the common turbocharger axis 2 and are connected to one another in terms of assembly.

The bearing housing 41 is arranged axially between the turbine housing 21 and the compressor housing 31 . The bearing housing 41 accommodates the rotor shaft 14 of the turbocharger rotor 10 and the bearing arrangement required for the axial bearing and for the rotary bearing of the rotor shaft 14 .

Another assembly of the exhaust gas turbocharger 1 is the turbocharger rotor 10, the rotor shaft 14, which is arranged in the turbine housing 21 turbine impeller 12 with a Impeller blading 121 and arranged in the compressor housing 31 compressor impeller 13 having an impeller blading 131. In other words, the turbine wheel 12 as well as the compressor wheel 13 have a plurality of blades which are arranged on a corresponding hub. The turbine wheel 12 and the compressor wheel 13 are arranged on the opposite ends of the common rotor shaft 14 and are non-rotatably connected thereto. The rotor shaft 14 extends axially through the bearing housing 41 in the direction of the turbocharger axis 2 and is rotatably mounted in it axially and radially about its longitudinal axis, the rotor axis of rotation 15 , with the rotor axis of rotation 15 coinciding with the turbocharger axis 2 . The turbocharger rotor 10 is mounted with its rotor shaft 14 by means of two radial bearings 42 and an axial bearing disk 43 . Both the radial bearing 42 and the axial bearing disk 43 are supplied with lubricant via oil supply channels 44 of an oil connection 45 .

The turbine housing 21 has one or more exhaust gas annular ducts, so-called exhaust gas flows 22 , arranged in a ring shape around the turbocharger axis 2 and the turbine impeller 12 , tapering helically towards the turbine impeller 12 . These exhaust gas flows 22 have a respective or common, tangentially outwardly directed exhaust gas supply channel 23 with a manifold connecting piece 24 for connection to an exhaust manifold (not shown) of an internal combustion engine, through which the exhaust gas mass flow AM flows into the respective exhaust gas flow 22 and then onto the turbine impeller 12 flows. The turbine housing 21 also has an exhaust gas discharge channel 26 which runs away from the axial end of the turbine impeller 12 in the direction of the turbocharger axis 2 and has an exhaust connection piece 27 for connection to the exhaust system (not shown) of the internal combustion engine. The exhaust gas mass flow AM emerging from the turbine impeller 12 is discharged into the exhaust system of the internal combustion engine via this exhaust gas discharge channel 26 .

Further details of the turbocharger 1 are not explained in more detail at this point. It should be noted that the in figure 1 described turbocharger 1 is to be understood as an example and alternatively can also have other configurations, without there being any restrictions for the following description of exemplary embodiments of the invention with reference to FIG Figures 4 to 6 result.

Figures 2 and 3 each show a meridional view of exhaust gas turbines 20 of a turbocharger 1, each of which has a turbine housing 21 and a turbine wheel 12 with a plurality of turbine blades 122. In figure 2 is a radial-axial turbine wheel and in figure 3 a radial turbine wheel is shown in a schematic half section. The rotor axis of rotation 15, which corresponds to an axis of rotation 123 of the turbine wheel 12, is shown in each case. In the representations of Figures 2 and 3 1 each depicts one of a plurality of turbine blades 122 typically disposed on the hub of turbine wheel 12 .

The turbines 20 of the two Figures 2 and 3 are exemplified by the figure 2 described.

The turbine wheel 12 has an upstream, axial end 124 and a downstream, axial end 125. As can be seen in the meridional view, the turbine blade 122 shown, like all other turbine blades, has a flow inlet edge 126 for the exhaust gas mass flow AM and a flow outlet edge 127 for the exhaust gas mass flow AM after exiting the turbine wheel 12 or the turbine blades 122. The flow inlet edge 126 and/or the flow outlet edge 127 can run obliquely or otherwise, approximately parallel, to the rotor axis of rotation 15, as shown in FIG Figures 2 and 3 is evident. The flow inlet edge 126 and the flow outlet edge 127 are connected via an outer contour 128 (English tip). The outer contour 128 lies directly opposite a housing contour 211 of the turbine housing 21 which surrounds the turbine wheel 12 . The housing contour 211 is designed to correspond to the outer contour 128, with a course of the two contours 128 and 211 in the view shown running essentially parallel to one another with respect to FIG Axis of rotation 123. The other turbine housing 21 is not shown for reasons of clarity.

It was recognized that the exhaust gas turbines shown 20 of Figures 2 and 3 can be defined by a number of parameters, which are explained below.

The flow entry edge 126 has a maximum entry radius R _in and the flow exit edge 127 has a maximum exit radius R _out . The outer contour 128 has an axial extension length L _axTiP in relation to the axis of rotation 123 or the axis of rotation 15 of the rotor. Outer contour 128 has an axial length portion L _cover of axial extent L _axTiP , in which a diameter of turbine wheel 12 is greater than a smallest diameter DA of turbine housing 21 at turbine blade outlet 129 for exhaust gas mass flow AM. Furthermore, the housing contour 211 and the outer contour 128 are spaced apart from one another in such a way that a minimal gap is formed, with a smallest radial distance Tip _clr between the housing contour 211 and the outer contour 128 prevailing.

As mentioned at the beginning, turbochargers can be damaged with various adverse consequences. Based on Figures 4 to 6 exemplary embodiments of turbines 20 are described which, in the event of damage to the turbocharger 1, enable the functions and advantages mentioned at the outset.

Dadurch werden die eingangs genannten Vorteile und Funktionen erreicht. Es sei an dieser Stelle erwähnt, dass das Verhältnis R_out zu R_in als Trim bezeichnet werden kann (s. Figur 5) . figure 4 shows a turbine 20, which is essentially the turbine of Figures 2 and 3 is equivalent to. The above parameter definitions apply analogously. In contrast to the described turbines Figures 2 and 3 the turbine 20 is designed in such a way that the figure 5 equation shown is satisfied. The condition is: $$\frac{L_{\mathit{covers}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{hint}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}.$$

This achieves the advantages and functions mentioned at the outset. It should be mentioned at this point that the ratio R _out to R _in can be called the trim (see Fig. figure 5 ) .

The turbine 20 is designed and manufactured, for example, in such a way that certain parameters are specified and the remaining parameters are determined using the conditions in order to obtain a necessary minimum value for L _Cover . Is advantageous, as well as in the figure 4 in contrast to the examples of Figures 2 and 3 it can be seen that the axial length portion L _cover is increased and matched to the turbine housing 21 . As a result, the turbine wheel 12 has an enlarged portion that is covered by the turbine housing 21 .

figure 6 shows a diagram in which the trim value is plotted on the x-axis and the ratio of L _cover to L _axTip is plotted on the y-axis. Three curves according to the equation are exemplary figure 5 shown, which are distinguished by the percentage values shown on the right next to the diagram, which result from the ratio Tip _clr to R _in .

Claims (10)

1. Turbocharger (1) for an internal combustion engine, having

   - a bearing housing (41), in which a rotor shaft (14) is mounted such that it can be rotated about a rotor rotational axis (15); and

   - an exhaust gas turbine (20) with a turbine wheel (12) which is arranged fixedly on the rotor shaft (14) for conjoint rotation and which has a runner blade system (121) with a plurality of turbine blades (122), and with a turbine housing (21) which is fixed mechanically on the bearing housing (41) and which surrounds the turbine wheel (12);
   wherein, with regard to a meridional view of the exhaust gas turbine (20),

   - at least one turbine blade (122) of the turbine wheel (12) has a flow inlet edge (126) and a flow outlet edge (127) for the exhaust gas mass flow (AM),

   - the flow inlet edge (126) has a maximum inlet radius R_in and the flow outlet edge (127) has a maximum outlet radius R_out, in each case in relation to the rotor rotational axis (15);

   - the at least one turbine blade (122) has an outer contour (128) which faces the turbine housing (21), extends from the flow inlet edge (126) as far as the flow outlet edge (127), and has an axial extent length L_axTip;

   - the turbine housing (21) has a housing contour (211) which lies opposite the outer contour (128);

   - the outer contour (128) of the at least one turbine blade (122) has an axial length portion L_cover of the axial extent L_axTip, in which a diameter of the turbine wheel is greater than a smallest diameter DA of the turbine housing at the turbine blade outlet for the exhaust gas mass flow AM; and

   - a smallest radial spacing Tip_clr is configured between the housing contour (211) and the outer contour (128) with regard to the rotor rotational axis (15); and wherein the exhaust gas turbine is characterized in that the turbine housing (21) and the turbine wheel (12) are configured and matched to one another in such a way that the following condition is met: $$\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\pi }{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)}.$$

   
2. Turbocharger (1) according to Claim 1, wherein the following applies to the ratio of Tip_clr to ${\mathrm{R}}_{\mathrm{in}}:\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\le$

   

   : 2.5%.
3. Turbocharger (1) according to either of the preceding claims, wherein the following applies to the ratio of Tip_clr to R_in: $\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\le 2.0\%$

   

   .
4. Turbocharger (1) according to one of the preceding claims, wherein the following applies to the ratio of Tip_clr to R_in: $\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\le 1.5\%$

   

   .
5. Turbocharger (1) according to one of the preceding claims, wherein the following applies to the ratio of L_cover to L_axTip: $\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>0.2$

   

   .
6. Turbocharger (1) according to one of the preceding claims, wherein the following applies to the ratio of L_cover to L_axTip: $\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>0.25$

   

   .
7. Turbocharger (1) according to one of the preceding claims, wherein the following applies to the ratio of L_cover to L_axTip : $\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>0.3$

   

   .
8. Turbocharger (1) according to one of the preceding claims, wherein the following applies to the ratio of R_out to R_in: $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}>0.8$

   

   , preferably $\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.95$

   

   , particularly preferably $0.8<\frac{R_{\mathit{out}}}{R_{\mathit{in}}}<0.95$

   

   .
9. Turbine wheel (12) for a turbocharger (1) according to one of the preceding claims, having a runner blade system (121) with a plurality of turbine blades (122), characterized

   in that the turbine wheel (12) is configured in such a way that the following condition is met: $$\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\pi }{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)},$$

   

   wherein, with regard to a meridional view of the turbine wheel (12),

   - at least one turbine blade (122) of the turbine wheel (12) has a flow inlet edge (126) and a flow outlet edge (127) for the exhaust gas mass flow (AM);

   - R_in describes a maximum inlet radius of the flow inlet edge (126) and R_out describes a maximum outlet radius of the flow outlet edge (127), in each case in relation to a rotational axis (123) of the turbine wheel (12) ;

   - L_axTip describes an axial extent length of an outer contour (128) of the at least one turbine blade (122), the outer contour (128) extending from the flow inlet edge (126) as far as the flow outlet edge (127), and facing a surrounding turbine housing (21) in proper operation;

   - L_cover describes an axial length portion of the axial extent L_axTip of the outer contour (128), in which a diameter of the turbine wheel is greater than a smallest diameter DA of the turbine housing at the turbine blade outlet for the exhaust gas mass flow AM;

   - Tip_clr describes a smallest radial spacing between a housing contour (211), lying opposite the outer contour (128) in proper operation, of the turbine housing (21) and the outer contour (128) with regard to the rotational axis (123) .
10. Method for producing a turbocharger (1) according to one of Claims 1 to 8, characterized
    in that it comprises the following steps:

    - determining and/or defining of the parameters of the maximum inlet radius R_in, the maximum outlet radius R_out, the axial extent length L_axTiP, the axial length portion L_cover and the smallest radial spacing Tip_clr in such a way that the following condition is met for the turbine wheel (12) and the turbine housing (21): $$\frac{L_{\mathit{cover}}}{L_{\mathit{axTip}}}>1-\frac{{\mathit{Tip}}_{\mathit{clr}}}{R_{\mathit{in}}}\times \frac{3\pi }{4}\times \frac{1}{\left(1-\frac{R_{\mathit{out}}}{R_{\mathit{in}}}\right)},$$

    

    and

    - manufacturing of the turbine wheel (12) and the turbine housing (21) on the basis of the parameters which are determined by means of the condition.

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