Iron material for high-temperature-resistant bearing bushings, bearing bushing made of said material, and turbocharger having such a bearing bushing

Abstract

Bearing bushings which are exposed to highly elevated temperatures during operation, corresponding high-temperature-resistant bearing bushings and exhaust-gas turbochargers having at least one such bearing bushing, include an iron material having a material composition which, apart from iron, has at least carbon, silicon, manganese, nickel, chromium, molybdenum and tungsten alloy constituents in certain amounts. This material composition ensures sufficient temperature resistance and self-lubricating properties with simultaneously good machining properties and a moderate price.

Claims

1. An iron material, comprising: a material composition including iron, Fe and at least alloy constituents within limit amounts stated below in percent by weight, wt. %: carbon, C: 1.5 to 3.0 wt. %; silicon, Si: 1.0 to 6.0 wt. %; manganese, Mn: 1.5 to 7.00 wt. %; nickel, Ni: 12.0 to 36.0 wt. %; chromium, Cr: 6.0 to 12.00 wt. %; phosphorus, P: 0.05 to 0.25 wt. %; copper, Cu: 0.5 to 7.5 wt. %; molybdenum, Mo: 2.0 to 5.0 wt. %; and tungsten, W: 0.8 to 2.0 wt. %, wherein the carbon constituent comprises free carbon incorporated into a structure of the iron material composition as lamellar graphite, nodular graphite, or vermicular graphite to improve self-lubrication properties of the iron material.

2. The iron material according to claim 1, wherein said material composition forms a high-temperature-resistant bearing bushing.

3. A bearing bushing for use under high-temperature conditions, the bearing bushing comprising or being manufactured from the iron material according to claim 1.

4. An exhaust-gas turbocharger, comprising: an exhaust-gas turbine; a fresh-air compressor; a bearing unit; at least one movable actuating apparatus for influencing fluid mass flows flowing through at least one of said exhaust-gas turbine or said fresh-air compressor; and at least one bearing bushing for use under high-temperature conditions, said at least one bearing bushing movably mounting said actuating apparatus, and said at least one bearing bushing including or being manufactured from the iron material according to claim 1.

5. The exhaust-gas turbocharger according to claim 4, wherein said at least one actuating apparatus is a wastegate valve, an overrun air recirculation valve or an adjustable turbine geometry.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows an exemplary embodiment of a bearing bushing according to the invention in a perspective illustration in a half-section on the left-hand side of the figure and in its entirety on the right-hand side of the figure;

(2) FIG. 2 shows an exemplary embodiment of an exhaust-gas turbocharger according to the invention in a perspective illustration with cutaway turbine housing.

DESCRIPTION OF THE INVENTION

(3) The example of a bearing bushing 1 according to the invention illustrated in FIG. 1 is composed of an iron material 2 according to the invention. The shape and dimensioning of such a bearing bushing may vary depending on design requirements. The illustrated example may for example be used as a bearing bushing for the rotary mounting of a crank spindle of a wastegate valve in the exhaust-gas turbocharger.

(4) FIG. 2 shows an exemplary embodiment of an exhaust-gas turbocharger 100 according to the invention with cutaway turbine housing 21. The sectional illustration provides an insight here into the structure and the mounting of the wastegate valve 10 with the crank arm operating device 11 and the operating actuator 19.

(5) As already described in the introduction, the exhaust-gas turbocharger has an exhaust-gas turbine 20, a fresh-air compressor 30 and a bearing unit 40. The exhaust-gas turbine 20 is equipped with a wastegate valve 10 and the exhaust-gas mass flow AM is indicated by arrows. The fresh-air compressor 30 has, for example, an overrun air recirculation valve (not illustrated). In general, a conventional exhaust-gas turbocharger 100, as illustrated in FIG. 2, has a multi-part construction. Here, a turbine housing 21 that is arrangeable in the exhaust tract of the internal combustion engine, a compressor housing 31 that is arrangeable in the intake tract of the internal combustion engine, and, between the turbine housing 21 and compressor housing 31, a bearing unit 40, are arranged adjacent to one another on a common turbocharger axis and are connected to one another in terms of assembly.

(6) The so-called turbocharger rotor 50 of the exhaust-gas turbocharger 100 is composed of the turbine impeller 22, the compressor impeller (not illustrated) and the rotor shaft (not illustrated).

(7) A further structural unit of the exhaust-gas turbocharger 100 is the turbocharger rotor 50, which has a rotor shaft (not illustrated), a turbine impeller 22 with an impeller blading arranged in the turbine housing 21, and a compressor impeller (not illustrated) with an impeller blading arranged in the compressor housing 31. The turbine impeller 22 and the compressor impeller are arranged on the opposite ends of the common rotor shaft and connected thereto for conjoint rotation. The rotor shaft extends in the direction of the turbocharger axis axially through the bearing unit 40 and is mounted rotatably therein, axially and radially about its longitudinal axis, the rotor axis of rotation 51, by means of radial bearings and an axial bearing, wherein the rotor axis of rotation 51 lies in the turbocharger axis, that is to say coincides therewith. The turbocharger rotor 50 rotates during operation about the rotor axis of rotation 51 of the rotor shaft. The rotor axis of rotation 51 and at the same time the turbocharger axis are illustrated by the indicated centerline and identify the axial orientation of the exhaust-gas turbocharger 100.

(8) As is apparent from FIG. 2 by way of example on the basis of the illustrated cutaway turbine housing 21 with wastegate valve 10, the crank arm operating apparatus 11 has a crank arm 12 arranged in the interior of the turbine housing 21, to which crank arm the plate-shaped valve flap 13 is attached. In the closed state of the wastegate valve 10, the valve flap 13 lies sealingly on the valve seat 14 and thus closes the bypass channel.

(9) The crank spindle 15 adjoining the crank arm 12 extends through the turbine housing 21 and is mounted in the turbine housing wall, so as to be rotatable about its axis, in a bearing bushing 1 according to the invention, which is manufactured from an iron material 2 according to the invention. Outside the turbine housing 21, an operating lever 18 is attached to the crank spindle 15, which operating lever is in turn engaged on, via further transmission elements of the crank arm operating apparatus 11, by an operating actuator 19. An overrun air recirculation valve (not illustrated) in the compressor housing 31 may in principle have the same or a similar structure.

(10) It is self-evident that the exhaust-gas turbocharger according to the invention is not limited to the exemplary embodiment illustrated in FIG. 2, but also encompasses other embodiments, for example with variable turbine geometries (VTG) and/or with adjustable compressor inlet openings and/or adjustable compressor diffusers and/or adjustable turbine outlet openings. In this case, the iron material according to the invention may advantageously be used wherever actuating parts are moved and, as a result, corresponding bearing points, in particular bearing bushings, are required.