DE102020114015B3 - Turbomachine for an internal combustion engine - Google Patents

Abstract

The invention relates to a turbo machine (1) for an internal combustion engine, comprising a shaft (2) and a roller bearing (3) for supporting the shaft (2), the roller bearing (3) having at least one inner ring (4a, 4b) and at least one outer ring (5) and between the at least one inner ring (4a, 4b) and the at least one outer ring (5) arranged rolling elements (6a, 6b), at least the at least one inner ring (4a, 4b) being made of a steel alloy, wherein the steel alloy at least 5.8 to at most 6.2% by weight nickel, at least 4.8 to at most 5.2% by weight chromium, at least 2.0 to at most 2.4% by weight aluminum, at least 0, 6 to at most 0.8% by weight of molybdenum and at least 0.45 to at most 0.55% by weight of vanadium.

Description

The invention relates to a turbo machine for an internal combustion engine or a turbo-compound engine. The field of application extends to turbo machines for internal combustion engines, for example turbochargers, electric turbo, turbo compressors, in particular e-chargers, and turbo-compound concepts in the automotive sector, namely passenger cars, commercial vehicles, heavy duty and off-road vehicles, and marine.

The turbomachine is preferably intended for use in internal combustion engines for trucks. The turbomachine comprises at least one shaft and a roller bearing for supporting the shaft. The roller bearing has at least one inner ring, at least one outer ring, and rolling elements that are spatially arranged between the inner ring and the outer ring.

Internal combustion engines are generally known, also called turbo-compound engines, in which the energy content of exhaust gases is utilized by a downstream power turbine in order to further relax the exhaust gases from the combustion. The energy recovered by the power turbine is then transferred to the crankshaft via a mechanical or hydraulic transmission, so that the efficiency and performance of the turbo-compound engine are optimized. When the exhaust valves open, the exhaust gases from the turbo-compound engine have a higher pressure than the ambient air, with at least part of this pressure gradient being used to drive the turbo-machine in order to compress the air in the intake tract of the turbo-compound engine.

From the DE 10 2010 054 904 A1 a bearing cartridge for a turbocharger is known. The bearing cartridge comprises a carrier ring that can be pressed into a bearing housing and a bearing outer ring radially encompassed by the carrier ring, an oil-filled gap being formed between the cylindrical outer surface of the bearing outer ring and the hollow cylindrical inner surface of the carrier ring, and the carrier ring having a supply bore designed to supply oil to the gap.

It is generally known that rolling bearing rings for turbochargers are made from tool steel. For example, the material M50 has established itself for this purpose, which is also known under the material number 1.3551. The production of rolling bearing rings from this material is expensive and complex.

The object of the present invention is to further develop a turbomachine and, in particular, to make the rolling bearings of the shaft of the turbomachine more cost-effective, more resistant and more durable. The object is achieved by the subject matter of claim 1. Preferred embodiments can be found in the dependent claims, the description and the figures.

A turbo machine according to the invention for an internal combustion engine comprises a shaft and a roller bearing for mounting the shaft, the roller bearing having at least one inner ring, at least one outer ring and rolling bodies spatially arranged between the at least one inner ring and the at least one outer ring, at least the at least one inner ring from a steel alloy is formed, the at least 5.8 to at most 6.2 wt .-% nickel, at least 4.8 to at most 5.2 wt .-% chromium, at least 2.0 to at most 2.4 wt .-% aluminum , at least 0.6 to at most 0.8 wt .-% molybdenum and at least 0.45 to at most 0.55 wt .-% vanadium.

The roller bearing can be formed from several individual bearing elements or as a bearing cartridge.

The respective alloy composition of the steel alloy can be determined for example by means of spectral analysis (OES) or by means of X-ray fluorescence analysis (XRF). % By weight is the abbreviation for percent by weight. The alloy components that are missing to 100% by weight and are not specified here and below are only formed by iron and unavoidable impurities.

The percentages by weight of the alloying elements nickel, chromium, aluminum, molybdenum and vanadium in the steel alloy enable the formation of rolling bearing rings that are particularly resistant to corrosion and oxidation, even at temperatures above 500 ° C, and have high dimensional stability. In particular, the steel alloy is produced by conventional melting and heat treatment, with production costs being reduced as a result. Furthermore, due to the percentages by weight of the alloying elements nickel, chromium, aluminum, molybdenum and vanadium, the temperature ranges for the formation of a martensitic structure are shifted in the direction of higher temperatures that there is no undercooling of the steel alloy, which in particular increases the dimensional stability of the workpiece becomes. In particular, such rolling bearing rings can be made more compact than rolling bearing rings made of the material 100Cr6, which also reduces the space required for the rolling bearing rings.

The percentage by weight of aluminum is made possible by the formation of a passive layer on the The surface of the workpiece has a high resistance to corrosion and oxidation. The passive layer is designed in particular as an aluminum oxide layer.

In addition to the abovementioned percentages by weight of the alloying elements nickel, chromium, aluminum, molybdenum and vanadium, the steel alloy preferably also has at least 0.16 to at most 0.31% by weight carbon. The steel alloy preferably has at least 0.25 to at most 0.31% by weight of carbon. In particular, the steel alloy has at least 0.27 to at most 0.29% by weight of carbon. This carbon content has proven to be advantageous for the formation of a martensitic structure and fine, homogeneously distributed alloy carbides that are smaller than 1 µm.

Furthermore, the steel alloy preferably has, in addition to the above-mentioned percentages by weight of the alloying elements nickel, chromium, aluminum, molybdenum and vanadium, at least 0.2 to at most 0.5% by weight manganese, at most 0.2% by weight silicon, at most 0.2% by weight of phosphorus and at most 0.001% by weight of sulfur. The percentage by weight of the alloying elements manganese, silicon, phosphorus and sulfur reduces the proportion of defects in the structure, which are formed in particular due to impurities, and thus increases the load-bearing capacity of the rolling bearing rings.

According to a preferred embodiment of the invention, the roller bearing has a first inner ring and a second inner ring, the first inner ring being arranged on the turbine side on the shaft and being formed from the steel alloy. In other words, the roller bearing comprises two inner rings and one outer ring. For example, only the turbine-side first inner ring is made from the steel alloy. An arrangement of the inner ring on the turbine side is to be understood as meaning that this inner ring adjoins a turbine of the turbomachine, in particular is directed towards the turbine of the turbomachine. On the turbine side, the gases have a higher temperature than on the compressor side.

According to a preferred embodiment of the invention, the second inner ring, which is arranged on the compressor side, is also made from the steel alloy. Thus, according to this embodiment, both the turbine-side first inner ring and the compressor-side second inner ring are made from the steel alloy. An arrangement of the inner ring on the compressor side is to be understood as meaning that this inner ring adjoins the compressor side of the turbomachine, in particular is directed towards the compressor side of the turbomachine.

According to a preferred embodiment of the invention, the outer ring, which is arranged on a housing, is also made from the steel alloy. Accordingly, according to this embodiment, both the turbine-side first inner ring and the compressor-side second inner ring and the outer ring are made from the steel alloy. This embodiment is particularly suitable for highly loaded roller bearings. The choice of rolling bearing rings that are made from the steel alloy is essentially dependent on the mechanical and thermal requirements that are placed on the turbo machine and, in particular, on the rolling bearing.

In particular, a structure of the steel alloy is martensitic and has alloy carbides and intermetallic phases. Alloy carbides with a diameter of less than 500 nm are preferably formed in the structure. In particular, the alloy _{carbides are designed as M 7} C ₃ , M ₆ C and MC carbides and embedded in the martensitic microstructure matrix, where “M” is the carbide-forming element, in particular iron, chromium, vanadium and molybdenum. The intermetallic phases are preferably nanocrystalline. For example, light microscopy and X-ray structure analysis are suitable for determining the proportions and size of the structural components of the steel alloy.

The steel alloy is preferably designed to be heat-treated at at least 500 to at most 620 ° C. in order to adjust the structure. In particular, the duration of the heat treatment is two to six hours, preferably three hours.

The steel alloy is preferably designed to be nitrided in order to increase the surface hardness and load-bearing capacity of the respective roller bearing ring. In other words, the respective rolling bearing ring is subjected to a stitching. Nitrogen penetrates the edge zone of the respective rolling bearing ring. In this thermochemical process, the edge zone is enriched with nitrogen at temperatures of 500 to 600 ° C.

According to a preferred embodiment of the invention, the shaft is designed to rotate in a speed range of 5,000 to 300,000 revolutions per minute. The shaft is preferably designed to rotate in a speed range of 50,000 to 300,000 revolutions per minute.

Further measures improving the invention are shown in more detail below together with the description of a preferred exemplary embodiment of the invention with reference to the single figure. The single figure shows a schematic longitudinal sectional illustration of a turbomachine according to the invention.

According to the single figure comprises a turbomachine 1 for an internal combustion engine - not shown here - a shaft 2 as well as a roller bearing 3 that is used to support the shaft 2 in one housing 7th is set up. The wave 2 is designed to rotate in a speed range of 100,000 to 300,000 revolutions per minute. The roller bearing 3 is in the present case designed as a double-row angular contact ball bearing and has a two-part inner ring 4a , 4b and a one-piece outer ring 3 on. Thus, the roller bearing 3 a first inner ring 4a , a second inner ring 4b , an outer ring 5 as well as spatially between the respective inner ring 4a , 4b and the outer ring 5 arranged rolling elements 6a , 6b on, on the respective raceways on the respective inner ring 4a , 4b and outer ring 5 roll off. The two inner rings 4a , 4b are rotationally fixed and axially fixed on an outer peripheral surface of the shaft 2 arranged. The outer ring 5 is radially and axially on an inner peripheral surface of the housing 7th the turbo engine 1 fixed. For axial fixation and anti-twist protection of the outer ring 5 is for example at least one screw 8th axially in the housing 7th screwed in.

Both inner rings 4a , 4b and the outer ring 5 are formed in the present case from a steel alloy that contains at least 5.8 to at most 6.2 wt.% nickel, at least 4.8 to at most 5.2 wt.% chromium, at least 2.0 to at most 2.4 wt. % Aluminum, at least 0.6 to at most 0.8% by weight molybdenum and at least 0.45 to at most 0.55% by weight vanadium. Furthermore, the steel alloy has at least 0.25 to at most 0.31% by weight of carbon. Furthermore, the steel alloy has at least 0.2 to at most 0.5% by weight manganese, at most 0.2% by weight silicon, at most 0.2% by weight phosphorus and at most 0.001% by weight sulfur.

The structure of the steel alloy is martensitic and has alloy carbides and intermetallic phases. To establish this structure, the steel alloy was heat-treated at a minimum of 500 to a maximum of 620 ° C. for a minimum of 2 to a maximum of six hours. Compared to previously known steel alloys for rolling bearings of turbo machines, this steel alloy has a higher thermal stability with improved fatigue strength at the same time. In particular, the resistance to corrosion and oxidation is increased and production is made easier.

List of reference symbols

1

Turbo engine

2

wave

3

roller bearing

4a, 4b

Inner ring

5

Outer ring

6a, 6b

Rolling elements

7th

casing

8th

screw

Claims (10)

Turbomachine (1) for an internal combustion engine, comprising a shaft (2) and a roller bearing (3) for supporting the shaft (2), the roller bearing (3) having at least one inner ring (4a, 4b), at least one outer ring (5) and has rolling bodies (6a, 6b) arranged spatially between the at least one inner ring (4a, 4b) and the at least one outer ring (5), at least the at least one inner ring (4a, 4b) being made of a steel alloy, characterized in that, the steel alloy at least 5.8 to at most 6.2% by weight nickel, at least 4.8 to at most 5.2% by weight chromium, at least 2.0 to at most 2.4% by weight aluminum, at least 0, 6 to at most 0.8% by weight of molybdenum and at least 0.45 to at most 0.55% by weight of vanadium. Turbomachine (1) according to Claim 1 , characterized in that the steel alloy further comprises at least 0.16 to at most 0.31% by weight of carbon. Turbomachine (1) according to one of the preceding claims, characterized in that the steel alloy has at least 0.25 to at most 0.31% by weight of carbon. Turbomachine (1) according to one of the preceding claims, characterized in that the steel alloy furthermore at least 0.2 to at most 0.5 wt .-% manganese, at most 0.2 wt .-% silicon, at most 0.2 wt .-% Phosphorus and at most 0.001% by weight sulfur. Turbomachine (1) according to one of the preceding claims, characterized in that the roller bearing (3) has a first inner ring (4a) and a second inner ring (4b), the first inner ring (4a) being arranged on the turbine side on the shaft (2) and is formed from the steel alloy. Turbomachine (1) according to Claim 5 , characterized in that the second inner ring (4b), which is arranged on the compressor side, is made of the steel alloy. Turbomachine (1) according to one of the preceding claims, characterized in that the at least one outer ring (5) which is arranged on a housing (7) is also made from the steel alloy. Turbomachine (1) according to one of the preceding claims, characterized in that a structure of the steel alloy is martensitic and has alloy carbides and intermetallic phases. Turbomachine (1) according to Claim 8 , characterized in that the steel alloy is designed to be heat-treated at at least 500 to at most 620 ° C in order to adjust the structure. Turbomachine (1) according to one of the preceding claims, characterized in that the shaft (2) is designed to rotate in a speed range of 5,000 to 300,000 revolutions per minute.

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