Turbocharger, having a steel material for high-temperature applications

Abstract

A turbocharger contains a turbine housing having an accommodating region for a turbine rotor disk of the turbocharger, which accommodating region is arranged centrally with respect to a turbine housing axis, and a turbine spiral channel, which tapers helically toward the accommodating region. A wastegate valve, having a spindle arm and a valve plate arranged on the spindle arm, or a variable exhaust-gas guiding device, having bearing disks and guide vanes, is arranged in the turbine housing. At least one of the: turbine housing, spindle arm and valve plate, or bearing disks and guide vanes, has a steel material for high-temperature applications. The material composition of which contains, in addition to iron, Fe, at least the following alloying constituents in amounts within the specified limits in weight percent: carbon: 0.4-0.5%; silicon: 1.25-1.75%; manganese: 3.0-12.0%; chromium: 19.5-20.5%; nickel: 5.0-6.0%; niobium: 1.00-1.5%. The material composition ensures sufficient temperature resistance of the components.

Claims

1. An exhaust-gas turbocharger, comprising: a turbine impeller; a turbine housing having a receiving region, disposed centrally with respect to a turbine housing axis, for said turbine impeller of the exhaust-gas turbocharger, said turbine housing having at least one turbine spiral duct tapering in a helical shape toward said receiving region for said turbine impeller; a wastegate valve with a spindle arm and a flap plate disposed on said spindle arm or a variable exhaust-gas guiding device with bearing disks and guide vanes, disposed in said turbine housing; and at least one component selected from the group consisting of said turbine housing, said spindle arm and said flap plate, and said bearing disks and said guide vanes, arc formed from a steel material for high-temperature applications, said steel material having a material composition containing iron, Fe, and at least the following alloy constituents in amounts within stated limits in percent by weight: carbon, C: 0.4-0.5%; silicon, Si: 1.25-1.75%; manganese, Mn: 3.0-12.0%; chromium, Cr: 19.5-20.5%; nickel, Ni: 5.0-6.0%; niobium, Nb: 1.00-1.5%; wherein said steel material contains at least five of further alloy constituents in proportions up to at most with stated amounts in percent by weight: tungsten, W: up to 0.6%; vanadium, V: up to 0.12%; copper, Cu: up to 0.25%; cobalt, Co: up to 1.0%; sulfur, S: up to 0.03%; and phosphorus, P: up to 0.04%.

2. The exhaust-gas turbocharger according to claim 1, wherein said steel material has at least one of said alloy constituents at least in amounts within the following limits in percent by weight: silicon, Si: 1.35-1.65%; and manganese, Mn: 7.0-12.0%.

3. The exhaust-gas turbocharger according to claim 1, wherein said steel material contains said at least one further alloy constituent in proportions of in each case at least in stated amounts in percent by weight: tungsten, W: at least 0.3%; vanadium, V: at least 0.06%; copper, Cu: at least 0.1%; cobalt, Co: at least 0.5%; sulfur, S: at least 0.013% and phosphorus, P: at least 0.02%.

4. The exhaust-gas turbocharger according to claim 1, wherein said steel material has a completely austenitic structure.

5. The exhaust-gas turbocharger according to claim 1, wherein said steel material has at least one of said alloy constituents at least in amounts within the following limits in percent by weight: silicon, Si: 1.35-1.65%; and manganese, Mn: 9.0-12.0%.

6. An exhaust-gas turbocharger, comprising: a turbine impeller; a turbine housing having a receiving region, disposed centrally with respect to a turbine housing axis, for said turbine impeller of the exhaust-gas turbocharger, said turbine housing having at least one turbine spiral duct tapering in a helical shape toward said receiving region for said turbine impeller; a wastegate valve with a spindle arm and a flap plate disposed on said spindle arm or a variable exhaust-gas guiding device with bearing disks and guide vanes, disposed in said turbine housing; and at least one component selected from the group consisting of said turbine housing, said spindle arm and said flap plate, or said bearing disks and said guide vanes formed from a steel material for high-temperature applications, said steel material having a material composition consisting essentially of iron, Fe, and at least the following alloy constituents in amounts within stated limits in percent by weight: carbon, C: 0.4-0.5%; silicon, Si: 1.25-1.75%; manganese, Mn: 3.0-12.0%; chromium, Cr: 19.5-20.5%; nickel, Ni: 5.0-6.0%; niobium, Nb: 1.00-1.5%; tungsten, W: up to 0.6%; vanadium, V: up to 0.12%; copper, Cu: up to 0.25%; cobalt, Co: up to 1.0%; sulfur, S: up to 0.03%; and phosphorus, P: up to 0.04%.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a schematically simplified illustration of an exhaust-gas turbocharger with a wastegate valve, in a half-sectional illustration, and

(2) FIG. 2 shows a three-dimensional illustration of an exhaust-gas turbocharger with a variable exhaust-gas guiding device, in a quarter-sectional illustration.

DETAILED DESCRIPTION OF THE INVENTION

(3) Parts which are identical in terms of function and designation are denoted by the same reference designations throughout the figures.

(4) The figure shows the basic structure of an exhaust-gas turbocharger 1, with a wastegate valve, as already described in broad terms in the introduction, in a schematically simplified half-sectional illustration.

(5) In general, a conventional exhaust-gas turbocharger 1 has, as illustrated in FIGS. 1 and 2, a multi-part structure. Here, a turbine housing 20, which is arrangeable in the exhaust tract of the internal combustion engine, a compressor housing 30, which is arrangeable in the intake tract of the internal combustion engine, and a bearing housing 40 between the turbine housing 20 and compressor housing 30 are arranged in series on a common turbocharger axis 2 and are connected to one another in terms of assembly. A further structural unit of the exhaust-gas turbocharger 1 is the turbocharger rotor 10, which has a rotor shaft 14, a turbine impeller 12, which is arranged in the turbine housing 20, and a compressor impeller 13, which is arranged in the compressor housing 30. The turbine impeller 12 and the compressor impeller 13 are arranged on the opposite ends of the common rotor shaft 14 and connected rotationally conjointly thereto. The rotor shaft 14 extends in the direction of the turbocharger axis 2 axially through the bearing housing 40 and is mounted in the axial and radial directions therein so as to be rotatable about its longitudinal axis, the rotor axis of rotation 15, wherein the rotor axis of rotation 15 lies on the turbocharger axis 2, that is to say coincides therewith. Here, the turbine housing axis 2a also lies in a line with the rotor axis of rotation 15 and the turbocharger axis 2. The exhaust-gas mass flow AM through the turbine housing 20 and the fresh-air mass flow FM through the compressor housing 30 are each illustrated by corresponding arrows.

(6) The turbine housing 20 has a turbine spiral duct 22, a so-called exhaust-gas channel, which is arranged in a ring around the turbocharger axis 2 and the receiving region of the turbine impeller 12 and tapers in a helical manner toward the receiving region and the turbine impeller 12, or possibly several in other versions. This exhaust-gas channel has an exhaust-gas feed duct 23, directed tangentially outward, with a manifold connector piece 24 for connection to an exhaust-gas manifold (not illustrated) of an internal combustion engine, through which manifold connector piece the exhaust-gas mass flow AM flows into the respective exhaust-gas channel. The exhaust-gas channel furthermore has an annular gap opening which runs at least over a part of the inner circumference, the so-called exhaust gas inlet gap 25, which runs in an at least partially radial direction toward the turbine impeller 12 and through which the exhaust-gas mass flow AM flows onto the turbine impeller 12.

(7) The turbine housing 20 furthermore has an exhaust-gas discharge duct 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 connector piece 27 for connection to the exhaust system (not illustrated) of the internal combustion engine. Via this exhaust-gas discharge duct 26, the exhaust-gas mass flow AM emerging from the turbine impeller 12 is discharged into the exhaust system of the internal combustion engine. The steel material SWst according to the invention, which characterizes the turbine housing 20 and from which the turbine housing 20 is manufactured, is symbolized by the cross-hatching.

(8) A wastegate valve 29 connects the exhaust-gas feed duct 23 upstream of the turbine impeller 12 in the flow direction of the exhaust-gas mass flow AM to the exhaust-gas discharge duct 26 downstream of the turbine impeller 12 in the flow direction of the exhaust-gas mass flow AM, via a wastegate duct 291 in the turbine housing 20. The wastegate valve 29 can be opened or closed by means of a closing device. This closing device has a spindle arm 292 which is rotatably mounted in the turbine housing 20 and on which a flap plate 293 is arranged. Both the spindle arm 292 and the flap plate 293 are in this example produced from the steel material SWst according to the invention. By actuation of the spindle arm 292 by means of an external actuator (not shown), the flap plate 293 is, in order to respectively close or open the wastegate valve 29, placed sealingly onto or lifted off from the valve seat 294 of the wastegate duct 291.

(9) By contrast, FIG. 2 shows an embodiment of an exhaust-gas turbocharger 1 with an exhaust-gas guiding device, in this case a variable turbine geometry 50, also referred to as VTG for short. Here, the basic construction of the exhaust-gas turbocharger 1 with turbine housing 20, compressor housing 30, bearing housing 40 and the turbocharger rotor 10 substantially corresponds to the exhaust-gas turbocharger 1 shown in FIG. 1. Instead of a wastegate valve, however, a VTG 50 is provided here. This is composed substantially of two annular bearing disks 51, 52, which are arranged with a certain spacing to one another in the annular-gap-shaped transition region between the turbine spiral duct 22 and the turbine impeller 12 and which thus form the exhaust-gas inlet gap 25. A plurality of guide vanes are arranged between the bearing disks 51, 52 in the exhaust-gas inlet gap 25 so as to be distributed over the circumference of the exhaust-gas inlet gap. These are received in rotatably mounted fashion at least in one of the bearing disks, and their rotational position can be set by means of an actuating mechanism 55 arranged on the rear side of said bearing disk and an external actuator (not illustrated). Both the turbine housing 20 and the bearing disks 51, 52 and the guide vanes 53 are in this embodiment composed of the steel material SWst according to the invention.