EXHAUST GAS TURBOCHARGER WITH AUXETIC STRUCTURES

Abstract

An auxetic material or auxetic structures in an exhaust gas turbocharger having a shaft and at least one compressor wheel arranged on the shaft, a turbine wheel and a housing in which the shaft, the compressor wheel, and the turbine wheel are arranged. At least one part of the housing includes an auxetic material with a negative Poisson's ratio.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an exhaust gas turbocharger.

2. Description of the Related Art

Conventional exhaust gas turbochargers are employed for increasing power and optimising combustion. For a good and complete combustion in the engine, a certain mixture ratio is necessary (stoichiometric fuel ratio). During the charging of the exhaust gas turbocharger, the density of the intake air is increased and the air quantity thus enlarged. Through the supercharging, the degree of filling and thus the efficiency of the internal combustion engine is significantly improved.

The heart of the turbocharger is the running gear consisting of turbine wheel with shaft and compressor wheel, which are arranged in a turbocharger housing. The turbine wheel is located on the exhaust gas side and is mostly permanently connected to the shaft. The compressor wheel is mounted on an opposite end of the rotor shaft. Depending on embodiment, the wheels are typically equipped with rotor blades and form a gap towards the housing on the end side. The gap width has a direct influence on the efficiency of the turbocharger. Depending on the rotational speed of the shaft, different elongation proportions also occur on the various rotating and non-rotating components—these thereby result in variable relative positions.

Thus, the gap between the blade tips and the housing wall changes as well. Regarding the elongation behaviour, attention is paid in particular to the so-called transient elongation behaviour between rotor and housing while passing through a cycle. This respective transient elongation behaviour of rotating and non-rotating components differs significantly. There is consequently a high risk for a gap bridging when the blade wheel tips rub against the housing. Such a risk of an instance of rubbing between housing and blade tip is present in particular during the running-up of the exhaust gas turbocharger.

In order to avoid dangerous and/or impermissible operating states in the transient operation between components that are moveable relative to one another, the nominal gaps are consequently dimensioned adequately large in the prior art. By way of this, a rubbing or bridging of the gap with contact on the housing during the transient operation can be avoided, but a gap that has been dimensioned correspondingly large leads to a reduced efficiency during the subsequent steady-state operation of the exhaust gas turbocharger.

In the event of bursting—during the failure of rotating components—dangerous situations with fragments of the exhaust gas turbocharger being flung about can develop. In the prior art, different burst protection devices are proposed for this purpose.

To prevent component fragments exiting in defined failure scenarios of rotating components, for example, solid wall thicknesses are provided in conventional housing structures and/or complex additional burst protection structures installed directly round about the housing. One aspect of the present invention is being able to do without elaborate burst protection design and/or solid flow-conducting housing structures.

Furthermore, there is the problem with exhaust gas turbochargers known from the prior art that components that are coupled to one another expand in their elongation behaviour significantly differently. In the case of conventional connections between such components, high screw stresses occur for example through elongation blockages and corresponding wear through relative movements in the contact surfaces. It is likewise desirable to realise an optimisation of these disadvantageous characteristics of elongation behaviour with the idea of one aspect of the present invention.

SUMMARY OF THE INVENTION

One Aspect of the invention is therefore based on overcoming the aforementioned disadvantages and propose an improved solution for an exhaust gas turbocharger, which has a safe operating behaviour with a high efficiency and in particular possesses an improvement regarding the problems of the transient elongation.

One aspect of the present invention is being able to do without elaborate burst protection design and/or solid flow-conducting housing structures. It is likewise desirable to realise an optimisation of these disadvantageous characteristics of elongation behaviour with the idea of one aspect of the present invention.

A basic idea of one aspect of the present invention is that the characteristics of materials with negative Poisson's ratio (transversal contraction number) in certain regions of the housing or of the turbocharger are used in order to specifically influence the elongation behaviour of affected regions.

According to one aspect of the invention, a new type of use of an auxetic material or of an auxetic structure with a negative Poisson's ratio is accordingly proposed in or on an exhaust gas turbocharger on a or between two adjacent components for influencing thermal and transient elongations.

In an advantageous configuration of the invention, a use of an auxetic material is proposed, wherein the auxetic material or the auxetic structure is arranged between two housing walls of a turbocharger housing, in hollow spaces of components of the exhaust gas turbocharger and/or between at least two components of the exhaust gas turbocharger adjoining one another, wherein in the last-mentioned case the auxetic material is preferentially provided as an elastic connecting element.

A further aspect of the present invention relates to an exhaust gas turbocharger with a shaft and at least a compressor wheel arranged on the shaft and a turbine wheel as well as a housing in which the shaft, the compressor wheel and the turbine wheel are arranged, wherein at least a part of the housing consists of an auxetic material with a negative Poisson's ratio.

In a preferred configuration of one aspect of the invention the housing comprises an inner housing wall and an outer housing wall and an intermediate space and the auxetic material (M) is arranged between the housing walls preferentially entirely in the intermediate space.

By integrating the auxetic structure in the compressor and/or turbine-side housing of a radial or axial exhaust gas turbocharger, the elongation behaviour of the housing can be adapted to the elongation behaviour of the rotor. The adaptation is effected through the targeted adjustment of the geometric parameters of the auxetic structure. The adjustment of the geometric parameters is effected in such a manner that taking into account transient thermal elongations and elongation proportions as a consequence of pressure and centrifugal force the elongation characteristic of the housing is adapted to the elongation characteristic of the rotor. By way of this, the radial gap that materialises during the steady-state operation is narrower compared with convention designs. As a result, a higher efficiency with turbines and a greater surge limit interval can be achieved with compressors.

It is advantageous, furthermore, when the auxetic material is entirely arranged in the region round about the compressor wheel and/or the turbine wheel, preferentially between the housing walls, as a result of which an additional safety effect for the event of a bursting of the turbocharger is established. Here, the auxetic structure is integrated in the housing structure as crash zone for absorbing kinetic energy during the impact of a rotating component and consequently increases the safety against components and/or component fragments exiting without a noteworthy increase in weight.

It is advantageous, furthermore, when between at least two adjoining components of the exhaust gas turbocharger an elastic connecting element is arranged, which consists of an auxetic material with a negative Poisson's ratio (for example between the bearing housing and the turbine inflow housing). The structure can be for example printed on or applied to a component or both components or be attached to the two components with connecting elements that are not described in more detail.

Alternatively, the two adjacent components can be directly connected to one another by way of the auxetic material.

In a further advantageous embodiment of the invention it is provided that hollow spaces are provided in the housing which are filled with the auxetic material. By suitably configuring the structure, the required stiffness is adjusted so that despite the low weight the requirements in terms of vibration are fulfilled.

It is likewise advantageous when auxetic material is coated on or applied to components of the exhaust gas turbocharger whose elongation is to be influenced.

The inventive concept can be used in particular with the following exhaust gas turbochargers: radial turbochargers, axial turbochargers, turbo blowers, or turbines (power turbine).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantageous further developments of the invention are marked in the subclaims or are shown by way of the figures in the following together with the description of the preferred embodiment of the invention. It shows:

FIG. 1 is a first schematic exemplary embodiment of the present invention; and

FIG. 2 is an alternative schematic exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In the following, the invention is explained in more detail making reference to the FIGS. 1 and 2, wherein same reference characters in the figures point to same structural and/or functional features.

In FIG. 1, a first purely schematic exemplary embodiment of the present invention is shown. Shown is an extract of a housing 3 of an exhaust gas turbocharger with a rotor L (e.g. a turbine wheel T or a compressor wheel V) with rotor blades 7. The rotor L is arranged on a shaft 2 in the housing 3.

The housing 3 has an inner housing wall 4 and an outer housing wall 5, wherein an auxetic material M or an auxetic structure with a negative Poisson's ratio is arranged between the two housing walls 4, 5.

Between the rotor blades 7 and the inner housing wall 4 a gap S is provided as intended.

In the shown exemplary embodiment, the auxetic material M is entirely arranged in the region round about the rotor L between the housing walls 4, 5.

FIG. 2 shows an alternative schematic exemplary embodiment of the present invention. Shown are a component B1 and a component B2 of an exhaust gas turbocharger, wherein between the two adjacent, i.e. adjoining components B1, B2 of the exhaust gas turbocharger an elastic connecting element 10 is arranged, which consists of an auxetic material M or of an auxetic structure M with a negative Poisson's ratio. There, the two adjacent components B1, B2 are directly connected to one another by the auxetic material M.

In its embodiment, the invention is not restricted to the preferred exemplary embodiments stated above. On the contrary, a number of versions is conceivable which also makes use of the presented solution even with embodiments of fundamentally different type.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1. An exhaust gas turbocharger comprising:

at least two adjacent components; and

one of an auxetic material or of an auxetic structure with a negative Poisson's ratio in or on the exhaust gas turbocharger between the at least two adjacent components configured to influence thermal and transient elongations.

2. The exhaust gas turbocharger of claim 1, wherein the auxetic material or the auxetic structure comprises an elastic connecting element arranged between the at least two adjacent components configured as two housing walls, in hollow spaces of components of the exhaust gas turbocharger or between the at least two adjacent components of the exhaust gas turbocharger adjoining one another.

3. An exhaust gas turbocharger comprising:

a shaft;

at least one compressor wheel arranged on the shaft;

a turbine wheel; and

a housing in which the shaft, the at least one compressor wheel, and the turbine wheel are arranged,

wherein at least a part of the housing has an auxetic material with a negative Poisson's ratio.

4. The exhaust gas turbocharger according to claim 3, wherein the housing comprises:

an inner housing wall; and

an outer housing wall;

wherein the auxetic material is arranged between the inner housing wall and the outer housing wall.

5. The exhaust gas turbocharger according to claim 3, wherein the auxetic material is entirely arranged in a region surrounding at least one of the at least one compressor wheel and the turbine wheel.

6. The exhaust gas turbocharger according to claim 3, further comprising:

an elastic connecting element arranged between at least two adjoining components of the exhaust gas turbocharger, the elastic connecting element comprises the auxetic material.

7. The exhaust gas turbocharger according to claim 6, wherein the at least two adjoining components are directly connected to one another by the auxetic material.

8. The exhaust gas turbocharger according to claim 3, wherein cavities are provided in the housing that are filled with the auxetic material.

9. The exhaust gas turbocharger according to claim 3, wherein the auxetic material is one of coated on or applied to components of the exhaust gas turbocharger.

10. The exhaust gas turbocharger according to claim 3, wherein the exhaust gas turbocharger is a radial turbocharger, an axial turbocharger, a turboblower, or a turbine.

11. The exhaust gas turbocharger according to claim 4, wherein the auxetic material is entirely arranged in a region surrounding at least one of the at least one compressor wheel and the turbine wheel between the inner housing wall and the outer housing wall.