DE102012219355A1 - Vane arrangement for exhaust gas turbocharger of motor car, has guide vanes arranged between cover disk and blade ring, where cover disk is made of ceramic material having high heat conductivity - Google Patents

Abstract

The arrangement (1) has guide vanes (3) to be placed rotatable over a blade ring stored at shovel journals (2). A cover disk (4) is spaced at the blade ring. The guide vanes are arranged between the cover disk and the blade ring. The cover disk is made of ceramic material having high heat conductivity of 120 Watts per meter Kelvin. The shovel journals are made of a metal i.e. steel, which comprises low thermal conductivity. A spacing element (5) is coaxially arranged at the shovel journals. Independent claims are also included for the following: (1) a supercharger (2) a motor car.

Description

The present invention relates to a guide vane arrangement, in particular for an exhaust gas turbocharger, and to an exhaust gas turbocharger with such a vane arrangement. The invention further relates to a motor vehicle with such an exhaust gas turbocharger.

As is known, exhaust gas turbochargers for internal combustion engines consist of two turbomachines: on the one hand from a turbine, on the other hand from a compressor. The turbine uses the energy contained in the exhaust gas to drive the compressor, which sucks in fresh air and introduces compressed air into the cylinders of the internal combustion engine. Because of the usually very high speed range of the internal combustion engine, a regulation of the exhaust gas turbocharger is required, so that as constant as possible boost pressure can be ensured in the largest possible speed range of the internal combustion engine. For this purpose, solutions are known, according to which a part of the exhaust gas flow is guided around the turbines by means of a bypass channel. However, an energetically more favorable solution allows the so-called variable turbine geometry, in which the Aufstauverhalten the turbine continuously changed and thus each of the entire exhaust gas can be used. Such a variable turbine geometry is realized in a conventional manner by means of adjustable guide vanes, by means of which the desired, flowing through an exhaust gas turbocharger exhaust stream can be variably adjusted.

For adjusting the vanes different adjustment mechanisms are known. The vanes are usually mounted on a vane support ring via a respective vane journal. Spaced to the vane support ring, a cover plate is disposed so that the vanes are disposed between this cover plate and the vane support ring. The cover plate may be made of a ceramic material.

The DE 10 2008 039 508 A1 describes a charging device of an exhaust gas turbocharger with a variable turbine geometry. The loading device comprises a blade bearing ring with guide vanes rotatably mounted thereon. On an opposite side of the vanes ring bearing ring an annular disc for covering the vanes is provided. The annular disc has a heat-insulating and a friction-reducing material.

It is an object of the present invention to provide an improved embodiment for a vane assembly.

This object is solved by the subject matter of the independent claims. Preferred embodiments are subject of the dependent claims.

The invention is based on the general idea to use for the cover plate of the vane arrangement, a ceramic material which has a high thermal conductivity. In this way, heat occurring in the vane arrangement can be dissipated quickly and effectively, so that the temperature load of a turbine housing, in which the vane arrangement according to the invention can be used, can be significantly reduced.

Ceramics with high thermal conductivity are largely made of inorganic, fine-grained raw materials with addition of water at room temperature molded and then dried objects, which are sintered in a subsequent firing above 900 ° C to hard, durable objects. Ceramic materials may have a very high thermal conductivity, whereby they are particularly predestined for the inventive use of a cover plate of a vane arrangement of an exhaust gas turbocharger. In addition, ceramic materials are also able to withstand high temperatures, such as occur in such an exhaust gas turbocharger, over long periods of time. Ceramic materials or coatings can be produced inexpensively and in almost any desired embodiment, whereby an economical use in industrial applications is possible.

In particular, by using ceramic materials with high thermal conductivity, a thermally induced expansion of individual components of the vane arrangement or of the exhaust gas turbocharger using the vane arrangement can be avoided. This in turn allows a reduction of a gap width between the guide vanes and the cover plate, since it is ensured by the inventive use of a cover plate with high thermal conductivity that a heat-related, unwanted thermal expansion of the vanes is avoided, so that no thermally induced friction effects between the vanes and the Cover disc (up to a jamming of the vanes) may occur.

Since the cover plate according to the invention thus enables a minimum gap width between the guide vanes and the cover plate, a bypass flow which reduces the efficiency of the guide vanes arrangement or the exhaust gas turbocharger using this guide vanes arrangement can be reduced or even completely eliminated by such a gap significantly improves the efficiency of the guide vane assembly and the exhaust gas turbocharger.

In an advantageous development of the solution according to the invention, the ceramic material may have a thermal conductivity of at least 120 W / mK. By using a ceramic material with such a high thermal conductivity (Ab-) heat can be removed particularly well from the vane arrangement.

In a particularly preferred embodiment, the ceramic material may be silicon nitride or silicon carbide. Silicon carbide is a group of carbides belonging to the chemical ceramic compound of silicon and carbon. Since silicon carbide has a high mechanical hardness and on the other hand a very high thermal conductivity (pure silicon carbide: about 350 W / mK, silicon carbide technical: up to 140 W / mK), it is as a ceramic material for the cover plate of the guide vane assembly according to the invention especially suitable.

The same applies to silicon nitride, which, in addition to its high strength, is characterized by a very low thermal expansion coefficient and a small modulus of elasticity. Ceramics made of silicon nitride can be used at temperatures up to about 1300 ° C and are therefore particularly well suited for use in exhaust gas turbochargers.

In a further embodiment, the vane support ring and / or the vanes and / or the vane trunnions may be made of a metal having a lower thermal conductivity than the thermal conductivity of the ceramic material. In this way, the cover plate according to the invention can be made of the ceramic material with high thermal conductivity with the other components of the vane arrangement such. the vane support ring, the vanes and the vane journal, which are usually made of a metal combined.

In a particularly preferred embodiment, the metal may have a thermal conductivity of at most 20 W / mK. In combination with a cover plate of the ceramic material with high thermal conductivity, which usually has at least 120 W / mK, heat from the vane arrangement and the turbine housing of an exhaust gas turbocharger using this guide vane arrangement can be dissipated particularly effectively.

In a particularly preferred embodiment, the metal may be a steel.

In order to ensure a particularly effective heat transfer through the cover plate of the vane arrangement, this can be formed entirely from the ceramic material in a further embodiment.

In an alternative or further embodiment, the cover plate may also comprise a cover layer of the ceramic material. This means that the actual cover plate does not have to be formed from the ceramic material according to the invention with high thermal conductivity. This allows a particularly cost-effective production of the cover plate, which may be made of a metal, in particular steel, for example, so that the material system of the cover plate and the remaining components of the vane assembly (vane support ring, etc.) may be identical. An advantage of such a design of the cover plate is that then all the essential components of the guide vane assembly are constructed from the same material system and thus also have a substantially identical thermal expansion coefficient.

In order to ensure a mechanically stable structure of the vane arrangement, in particular when used in a turbine housing of an exhaust gas turbocharger, in a particularly preferred embodiment the vane arrangement can have at least one spacer which is arranged coaxially with the vane journal and the vane support ring at a distance from the cover disk holds.

The invention also relates to an exhaust-gas turbocharger, in particular for a motor vehicle, with a guide-blade arrangement having one or more of the features explained above and with a turbine housing with a housing wall facing the guide-blade arrangement, on which the cover disk of the guide-blade arrangement is arranged. The exhaust-gas turbocharger further comprises a bearing housing and a spring element supported on the bearing housing, by means of which a pressure force is generated on the at least one spacer element in the axial direction via the guide-blade carrier ring, so that this presses the cover disk against the turbine housing for axial fixation.

The invention further relates to a motor vehicle having an internal combustion engine as well as having an exhaust gas turbocharger operatively connected thereto for increasing the output of this internal combustion engine with the features explained above.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

A preferred embodiment of the invention is illustrated in the drawing and will be explained in more detail in the following description.

In the presentation of the 1 a guide vane arrangement according to the invention is shown and with 1 designated. The vane arrangement 1 rotatably via a respective vane journal on a vane support ring 2 mounted vanes 3 , where in the partial view of 1 by way of example, only a single such vane 3 and accordingly, only a single associated blade bearing journal is shown. The vane arrangement 1 further includes a vane support ring 2 spaced cover disc 4 , wherein the vanes 3 each between the cover disc 4 and the vane support ring 2 are arranged. The cover disk 4 has a ceramic material, which in turn has a high thermal conductivity. The thermal conductivity of the ceramic material may have a thermal conductivity of at least 120 W / mK, such that waste heat occurring in the vane assembly, such as when the vane assembly 1 used in an exhaust gas turbocharger, can be discharged to the outside in an effective manner. The ceramic material may be silicon nitride or silicon carbide. Silicon carbide is a group of carbides belonging to the chemical ceramic compound of silicon and carbon. Since silicon carbide on the one hand has a high mechanical hardness and on the other hand a very high thermal conductivity (pure silicon carbide: about 350 W / mK, technical silicon carbide: up to 140 W / mK), it is as a ceramic material for the cover plate of the guide vane according to the invention Arrangement particularly well suited. The same applies to silicon nitride, which, in addition to its high strength, is characterized by a very low thermal expansion coefficient and a small modulus of elasticity. Ceramics made of silicon nitride can be used at temperatures up to about 1300 ° C and are therefore particularly well suited for use in exhaust gas turbochargers. In principle, however, other ceramic materials with high thermal conductivity come into consideration.

The vane carrier ring 2 may be made of a metal or other suitable material, which has a lower thermal conductivity than the thermal conductivity of the ceramic material. The same applies to the guide vanes and / or the vane journal. For example, these components of the vane assembly may be made of a metal (eg, steel) having a thermal conductivity of at most 20 W / mK.

In a first variant, the cover disc 4 be formed entirely of the ceramic material with high thermal conductivity, resulting in a particularly effective removal of heat through the cover plate 4 allows. Alternatively, the cover disk 4 but also be formed of a different material system with lower thermal conductivity than the ceramic material with high thermal conductivity and have a cover layer of the ceramic material with high thermal conductivity. This allows a particularly cost-effective production of the vane arrangement 1 ,

For example, the cover disk 4 in this case be made of the same material, such as metal or steel, as the other components of the vane assembly 1 such as the vane support ring 2 or the vanes 3 , In this case, then all components have substantially identical physical properties. In particular, in this case, the thermal expansion coefficient of the cover plate and the remaining components is the same.

The vane assembly may include at least one spacer 5 which is arranged coaxially with the vane journal and the vane support ring 2 at a distance to the cover disk 4 holds. The vane arrangement 1 can be part of an exhaust gas turbocharger. Such an exhaust gas turbocharger may be a turbine housing 6 which in the 1 only partially shown. The turbine housing 6 can be one of the vane assembly 1 facing housing wall 7 have, on which the cover plate 4 the vane arrangement 1 is arranged.

The exhaust gas turbocharger may also have a likewise only partially shown bearing housing 8th exhibit. On the bearing housing 8th can a spring element 9 supported by means of which in the axial direction A via the vane support ring 2 a compressive force (see arrow D) on the at least one spacer element 5 is generated, so this is the cover disk 4 for axial fixation against the turbine housing 6 suppressed.

The exhaust gas turbocharger can be used together with an internal combustion engine in a motor vehicle, wherein the exhaust gas turbocharger for increasing the performance of the internal combustion engine can be in operative connection with this.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008039508 A1 [0004]

Claims (10)

Guide vane arrangement ( 1 ), in particular for an exhaust-gas turbocharger, with-rotatable via a respective blade-bearing journal on a guide-blade carrier ring ( 2 ) mounted guide vanes ( 3 ), - with a guide vane ring ( 2 ) spaced cover plate ( 4 ), wherein the guide vanes ( 3 ) between the cover disc ( 4 ) and the vane carrier ring ( 2 ) are arranged, - wherein the cover plate ( 4 ) has a ceramic material, - characterized in that the ceramic material has a high thermal conductivity. Guide vane arrangement ( 1 ) according to claim 1, characterized in that the ceramic material has a thermal conductivity of at least 120 W / mK. Guide vane arrangement ( 1 ) according to claim 1 or 2, characterized in that the ceramic material is silicon nitride or silicon carbide. Guide vane arrangement ( 1 ) according to one of claims 1 to 3, characterized in that the guide vane support ring ( 2 ) and / or the guide vanes ( 3 ) and / or the vane journal are made of a metal which has a lower thermal conductivity than the thermal conductivity of the ceramic material. Guide vane arrangement ( 1 ) according to claim 4, characterized in that the metal has a thermal conductivity of at most 20 W / mK. Guide vane arrangement ( 1 ) according to claim 4 or 5, characterized in that the metal is a steel. Guide vane arrangement ( 1 ) according to one of the preceding claims, characterized in that the cover disc ( 4 ) is formed entirely of the ceramic material. Guide vane arrangement ( 1 ) according to one of the preceding claims, characterized in that the vane arrangement ( 1 ) at least one spacer element ( 5 ) which is arranged coaxially to the vane journal and the guide vane support ring ( 2 ) at a distance to the cover disk ( 4 ) holds. Exhaust gas turbocharger, in particular for a motor vehicle, - with a vane arrangement ( 1 ) according to one of the preceding claims, - with a turbine housing ( 6 ) with one of the vane arrangement ( 1 ) facing housing wall ( 7 ), on which the cover disc ( 4 ) of the vane arrangement ( 1 ), - with a bearing housing ( 8th ), - with one on the bearing housing ( 8th ) supporting spring element ( 9 ), by means of which in the axial direction (A) via the guide vane support ring ( 2 ) a pressure force on the at least one spacer element ( 5 ) is generated so that this the cover disc ( 4 ) for axial fixation against the turbine housing ( 6 ) presses. Motor vehicle, With an internal combustion engine, - With an increase in performance of the internal combustion engine with this operatively connected exhaust gas turbocharger according to claim 9.

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