The present invention relates to a multi-stage turbocharger arrangement (1), having a high-pressure turbocharger (20) which has a turbine housing (26A), a bearing housing (27A), a compressor housing (28A); and having a low-pressure turbocharger (21) which has a turbine housing (26B), a bearing housing (27B), a compressor housing (28B); wherein the turbine housings (26A, 26B) are combined to form at least one turbine housing unit (26), and/or wherein the bearing housings (27A, 27B) are combined to form at least one bearing housing unit (27), and/or wherein the compressor housings (28A, 28B) are combined to form at least one compressor housing unit (28).

This application claims the benefit of German Application Serial No. 10 2009 031026.6 filed Jun. 29, 2009 and PCT Application Serial No. 2010/039756 filed Jun. 24, 2010.

The invention relates to a multi-stage turbocharger arrangement for an internal combustion engine, as per the preamble of claim1.

Conventional multi-stage turbocharger arrangements known from the prior art are generally constructed from at least two turbochargers which are arranged in series and whose compressor housing, bearing housing and turbine housing are connected to one another by means of flanges or other connecting elements. Said design entails a large structural volume and an increased weight, and resulting high production costs of multi-stage turbocharger arrangements of said type. Furthermore, the multi-stage turbocharger arrangements of the prior art have inadequate heat dissipation or cooling on account of the high thermally active mass of the structure and the large internal surface area of the exhaust-gas flow ducts. As a result, thermal stresses arising on account of the high temperature differences between the individual assemblies can be prevented only to an inadequate extent, which adversely affects the service life of individual components.

It is therefore an object of the present invention to provide a multi-stage turbocharger arrangement which has a simplified structure having more efficient cooling and which avoids the abovementioned disadvantages of the prior art.

Said object is achieved by means of the features of claim1.

A simpler structure having a smaller structural volume compared to the turbocharger arrangements of the prior art can be achieved through the combination of the turbine, bearing and compressor housings of the high-pressure turbocharger and low-pressure turbocharger to form a common turbine housing unit, bearing housing unit and compressor housing unit.

The subclaims relate to advantageous refinements of the invention.

The combined housing arrangement permits simpler and cheaper production and machining of the individual housing parts of the multi-stage turbocharger arrangement overall.

As a result of the specific structure of the turbocharger arrangement according to the invention, the heat quantity transferred from the exhaust gas into the outer housing parts is drastically reduced.

Furthermore, an improvement in insulation is obtained by means of an air gap between the exhaust-gas ducts and housing parts.

The use of an expandable inner jacket arrangement for conducting exhaust gas in the flow ducts is also advantageous.

Furthermore, a limitation of the thermal expansion/material stresses can be achieved by means of additional cooling which, in particular by using a separate cooling liquid, ensures a virtually constant temperature in the outer housing parts.

The individual inner and outer housing parts, which are arranged substantially parallel to one another, may also be connected to one another in a simple manner by means of screw connections, welded connections or clamping connections.

Furthermore, the outer housing parts may be produced from housing materials which are easy to cast and/or to machine, such as for example aluminum, steel, magnesium, plastic or combinations of further different materials.

By means of the turbocharger arrangement according to the invention, a significantly smaller hot internal surface of the exhaust-gas flow ducts and a correspondingly lower radiation of heat (in particular in the warm-up phase) is obtained as a result of the increased degree of integration of the arrangement.

It is also possible for two or more shaft/bearing arrangements to be arranged in one of the housings.

Cooling of the housing which contains the two/plurality of shafts/bearings may also take place. A substantially parallel arrangement of the shafts is also possible.

Use may also be made of a bushing (similar to a bearing cartridge), which is inserted into the outer shall, for supporting the bushes and rotating shafts.

Furthermore, the outer housing parts may be produced as pressure-die-cast parts or using other known casting processes.

It is also possible for the compressor spirals to be arranged with an axial offset relative to one another in the shaft direction.

The turbine spirals may also be split perpendicularly to the shafts in order to allow the inner shell to be inserted.

The turbine and compressor spirals may be arranged such that the projections overlap as viewed in the shaft direction in order to obtain a minimum structural volume.

It is also possible for the oil supply and the oil discharge for both bearing systems to be cast or drilled into the housings.

By means of the turbocharger arrangement according to the invention, it is possible for the coolant to flow through some or all of the outer housings. Furthermore, the coolant can flow from one housing to the other.

Furthermore, an integration of the bypass duct of the high-pressure turbine as part of the inner shell and in the outer housing is obtained.

An integration of the wastegate valve of the low-pressure turbine as part of the inner shell is also obtained.

Furthermore, the bypass valve of the low-pressure turbine may be integrated in the outer housing.

The manually actuated compressor bypass valve may also be replaced with an automatic valve.

It is alternatively possible for the wastegate valve of the low-pressure turbine, the wastegate valve of the high-pressure turbine and the bypass valve of the high-pressure compressor to be eliminated.

The bearing arrangement may also be designed such that oil can flow in any direction, with an arrangement in a vertically mirrored position being possible.

Furthermore, the bearing arrangement may be designed such that an arrangement in a rotated position is possible.

The spirals and housings may be designed such that a plurality of different spiral and impeller sizes can be arranged therein.

The turbochargers of the multi-stage turbocharger according to the invention may additionally have a variable turbine geometry.

The multi-stage turbocharger arrangement may be used for sequential turbo charging.

The multi-stage turbocharger arrangement may be used for supercharging using two parallel turbochargers.

With reference toFIG. 1, an embodiment of the multi-stage turbocharger arrangement1according to the invention will be described below. As can be seen from

FIG. 1, the multi-stage turbocharger arrangement1has a high-pressure turbocharger20, which has a high-pressure turbine4which is connected by means of a shaft14to a high-pressure compressor10, and a low-pressure turbocharger21, which has a low-pressure turbine6which is connected by means of a shaft15to a low-pressure compressor9. The high-pressure turbine4and the low-pressure turbine6are arranged in a common turbine housing unit26, which is divided into a turbine housing section26A of the high-pressure turbocharger20and a turbine housing section26B of the low-pressure turbocharger21. An inner shell23which can expand as a result of heat is inserted into the interior of the turbine housing unit26, in the interior of which inner shell23hot engine exhaust gas Ag flows through the high-pressure turbine4and the low-pressure turbine6. Formed between the inner shell23and the turbine housing unit26is an air gap22which insulates the inner shell23, which is heated by the engine exhaust gas Ag, with respect to the turbine housing unit26. Furthermore, the turbine housing unit26has formed in it cooling ducts24for a coolant which flows therein which reduces the temperature of the turbine housing unit26or keeps said temperature at a level which is admissible in all operating states of the turbocharger arrangement1.

Also formed in the turbine housing section26A of the high-pressure turbocharger20is a bypass5of the high-pressure turbine4, which bypass5has a regulating valve5aby means of which the engine exhaust gas Ag bypasses the high-pressure turbine4when the regulating valve5ais open. Furthermore, a wastegate arrangement7is formed in the turbine housing section26B of the low-pressure turbocharger21, in the interior of which wastegate arrangement7is arranged a wastegate valve7a. When the wastegate valve7ais open, a part of the flow of the engine exhaust gas Ag can bypass the low-pressure turbine6and flow directly into an exhaust8(seeFIG. 2).

The shaft14of the high-pressure turbocharger20and the shaft15of the low-pressure turbocharger21are mounted in a common bearing housing unit27which is assembled from a bearing housing section27A of the high-pressure turbocharger20and a bearing housing section27B of the low-pressure turbocharger21. The bearing housing unit27has a cooling duct25, the coolant which flows therein cooling the bearing housing unit27with respect to the adjacent inner shell23of the turbine housing unit26.

The high-pressure compressor10of the high-pressure turbocharger20and the low-pressure compressor9of the low-pressure turbocharger21are arranged in a common compressor housing unit28which is assembled from a compressor housing section28A of the high-pressure turbocharger20and a compressor housing section28B of the low-pressure turbocharger21and which is closed by means of a compressor cover29. As can be seen from the illustration ofFIG. 1, the high-pressure compressor10is partially also formed in the bearing housing unit27and the low-pressure compressor9is partially also formed in the compressor cover29.

As can also be seen fromFIG. 1, air L is supplied to the low-pressure compressor9from the outside via a duct16formed in the compressor cover29, which duct16, over its further profile, is formed in the compressor housing unit28between the low-pressure compressor9and the high-pressure compressor10, and runs through the bearing housing unit27, the compressor housing unit28and the compressor cover29downstream of the high-pressure compressor10. Furthermore, a compressor bypass duct11is formed in the compressor cover29in the region of the high-pressure compressor10, which compressor bypass duct11comprises a compressor bypass valve11a. Through said compressor bypass duct11, the charge air L can be conducted entirely or partially around the high-pressure compressor10in order to prevent throttling of the high-pressure compressor10at large air flow quantities.

The connecting surfaces, which are formed substantially parallel to one another, of the common turbine housing unit26, bearing housing unit27and compressor housing unit28are connected to one another by means of screw connections, welded connections, adhesive connections and/or clamping connections, even if this is not illustrated inFIG. 1.

The high-pressure turbine4and the low-pressure turbine6or the low-pressure compressor9and the high-pressure compressor10can each have a variable turbine geometry which, inFIG. 2, is denoted by way of example by the reference symbol4ain the case of the high-pressure turbine4. Furthermore, the compressor bypass valve11amay be an automatic or regulated valve, and the wastegate valve7amay be omitted in some arrangements in order to save costs.

In the embodiment of the multi-stage turbocharger arrangement according to the invention illustrated inFIG. 1, the hot exhaust gas flows only in the inner shell23, which is arranged in a sandwich-like manner between the turbine housing unit26and the bearing housing unit27, which have the cooling ducts24and25, in order to prevent overheating of the turbine housing unit26and of the bearing housing unit27. The cooling ducts24and21may alternatively also be connected to one another. In further conceivable embodiments, the housing units26,27and28may also be divided differently than in the embodiments illustrated here. Furthermore, it is alternatively also possible for all the housing units to be cooled or for only parts of the exhaust gas flow ducts to be insulated by an air gap.

FIG. 2shows a schematically simplified illustration of a multi-stage turbocharger arrangement of the prior art, as is used for example in a conventional two-stage turbocharger system of a diesel engine. Here, identical components are denoted by the same reference symbols as inFIG. 1. The multi-stage turbocharger arrangement10illustrated inFIG. 2indicates the flow profile of the exhaust gas Ag of an engine2from an exhaust manifold3to the discharge through an exhaust8, and the flow profile of the inducted air L through an intake line16to an intake manifold13of the engine2. Said conventional turbocharger arrangement is known in numerous similar designs and variations, the construction of which will however not be described in any more detail here.

The multi-stage turbocharger arrangement according to the invention has a significantly smaller number of components and a lower overall weight in relation to the known turbocharger arrangements of the prior art. Furthermore, the comparatively significantly smaller structural volume is of great advantage during the installation of the turbocharger systems.

To supplement the disclosure, reference is explicitly made to the diagrammatic illustration of the invention inFIG. 1.

LIST OF REFERENCE SYMBOLS

1Multi-stage turbocharger arrangement2Engine3Exhaust manifold4High-pressure turbine4aVariable turbine geometry5Bypass of the high-pressure turbine5aRegulating valve6Low-pressure turbine7Wastegate arrangement7aWastegate valve8Exhaust9Low-pressure compressor10High-pressure compressor11Compressor bypass duct11aCompressor bypass valve12Charge-air cooler13Intake manifold14Shaft of the high-pressure turbocharger15Shaft of the low-pressure turbocharger16Duct20High-pressure turbocharger21Low-pressure turbocharger22Air gap23Inner shell24Cooling duct in the turbine housing unit25Cooling duct in the bearing housing unit26Turbine housing unit26A Turbine housing section of the high-pressure turbocharger26B Turbine housing section of the low-pressure turbocharger27Bearing housing unit27A Bearing housing section of the high-pressure turbocharger27B Bearing housing section of the low-pressure turbocharger28Compressor housing unit28A Compressor housing section of the high-pressure turbocharger28B Compressor housing section of the low-pressure turbocharger29Compressor coverAg Engine exhaust gasL Inducted air