WO2010036532A2

WO2010036532A2 - Turbocharger and subassembly for bypass control in the turbine casing therefor

Info

Publication number: WO2010036532A2
Application number: PCT/US2009/056893
Authority: WO
Inventors: Gerald Schall
Original assignee: Borgwarner Inc.
Priority date: 2008-09-25
Filing date: 2009-09-15
Publication date: 2010-04-01
Also published as: CN102149910B; KR20110063665A; WO2010036532A3; JP2012503742A; DE112009002098T5; JP5645828B2; US20110175025A1; KR101576196B1; CN102149910A

Abstract

The invention relates to a subassembly for bypass control in the turbine casing of a turbocharger, in particular in a diesel engine, and to an exhaust gas turbocharger with a subassembly for bypass control in the turbine casing of the turbocharger.

Description

TURBOCHARGER AND SUBASSEMBLY FOR BYPASS CONTROL IN T~Ε

TURBINE CASING THEREFOR

DESCRIPTION

The inversion relates to a subasserrbiy for bypass control m the turbine casirg of a turbocharger, in particular i" a diesel engine, according to the preamble of claim 1, and also to an exhaust gas turbocharger with a subassembly for bypass control m the turbine casing of the turbocharger, according to the preamble of claim 10.

Exhaust gas turbcchargers are systems for increasing the power of piston engines. Ir an exhaust gas turbocharger, the energy of the exhaust gases is used for increasing the power. The power increase results from a rise in the mixture throughput per working stroke.

A turbccharger consists essentially of an exhaust gas turome with a shaft and with a compressor, the compressor arranged m the intake tract of the engine being coⁿnected to the shaft, a^d the blade wheels located in the casing cf the exhaust gas turbine and in the compressor rotating.

Exhaust gas turbochargers are know" which allow multi-stage, that is to say at least two-stage supercharging, so that even more power can be generated from the exhaust gas jet. Such multi-stage exhaust gas turbochargers have a special set-up which comprises a regulating member for h_ghly dynamic cycl_c stresses, to be precise a subassembly for bypass control m the turbine casing of the exhaust gas turbocharger, such as, for example, in particular a flap plate, a lever or a spmαle. The subassembly for bypass control in the turbine casing of the exhaust gas turbocharger has to satisfy extremely stringent material requirements. The material forming the individual components of the subassembly for bypass control must be heat-resistant, that is to say still offer sufficient strength even at very high temperatures of at least up to about 850⁰C. Furthermore, the material must have good resistance to the break-up of grain boundaries during casting. If the material is resistant to the break-up of grain boundaries, complex filling geometries, even with thin wall thicknesses, can consequently be implemented during precision casting, this being a decisive criterion particularly in the case of the fine geometric parts of the subassembly for bypass control in the turbine casing of an exhaust gas turbocharger. Furthermore, the ductility of the material must be sufficiently high, so that, under overload, the parts are not subjected to plastic deformation and do not break.

An exhaust gas turbocharger with a double-flow exhaust gas inlet duct is known from DE 10 2007 018 617 Al.

The object of the present invention, then, was to provide a subassembly for bypass control in the turbine casing of a turbocharger, according to the preamble of claim 1, and a turbocharger according to the preamble of claim 10, which has improved temperature resistance and is distinguished by good resistance to the break-up of the grain boundaries during the casting of the material. Moreover, the subassembly for bypass control should have high ductility, be stable and have low susceptibility to wear.

The object is achieved by means of the features of claim 1 and of claim 10. What is achieved by tne design according to the invention of the subassernbly for ϋypass control in the turυme casing of a turbociarger, consisting of an iren-based alloy with a carbide microstructure and dispersions of at least one eleirent or one compound of the "rare earths" anct/or Y₂O , is that th^ material which ultimately provides the subassemoly for bypass control m the turbine casing is distinguished by especially good strength and stability. Tne stability of the material according to the invention is promoted, in part_c~lar, m that the material has hig^ resistance to the break-up of gram bouⁿdaries. It is presumed that the gram boundary cohesion is increased by means of at least one element a^d/or one compoαnd of the "rare earths" or Y_?0 . It seems that _^t is precisely these chemical elements wh_ch are elemerts effective ir terms of gram boundaries and bring about a staoilization of the material even during its production.

Without being mvol\ed m theory, it is presumed that it is precisely the iron-based alloy according to the invention with a carbiαe microstructure which has a property profile balanceo fcr the mtenaed use, to be precise sufficient strength alo^g with very good ouctility. Furthermore, the material is distinguished by high staoility and therefore _ow wear, even under load at high temperatures, that is to say temperatures of up to 870⁰C.

It has Deen shown that dispersions into the iron-based alloy of at least one elemert or ore compound of the "rare earths" and/or Y₂O counteract the lattice slip under high-temperature conditions, thus additioⁿally bringing about a stabilization of the material, m t^at the break-up of the gram ooundaries _s prevented or markedly reduced. Moreover, the fine dispersoids of the elements or compounds of the "rare earths" and/or of the Y₂O₁ reinforce the dislocation anchoring, so that, during the casting of the material and the generation of the final form, the material is so stable that even complex filling geometries, even with extremely thin wall thicknesses, can be produced.

The subassembly according to the invention is distinguished by a temperature resistance of up to

870⁰C, which is attributable to the unique composition of the material and the balanced ratio in the iron alloy which has a carbide microstructure, in combination with at least one element or one compound of the "rare earths" and/or Y₂O-.

Furthermore, the long-term rupture strength of the subassembly according to the invention for bypass control in the turbine casing of a turbocharger is considerably improved.

The subassembly according to the invention for bypass control in the turbine casing of a turbocharger is understood to mean all structural parts which are part of the regulating member for the highly dynamic cyclic stress, in particular a flat plate, lever, bush or spindle. The subassembly according to the invention for bypass control is preferably one which is employed in a multi-stage or at least two-stage exhaust gas turbocharger.

The term "rare earths" is understood to mean all elements which are gathered together in the periodic system of elements under the definition "lanthanoids", that is to say essentially lanthanum, cerium, praseodymium, samarium, europium, gadolinium, terbium, — S —

dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

The teim "element" is to be understood as meaning both the pure chemical element and conpounds thereof, i" particular its oxides.

The subclaims contain advantageous developmeⁿts of t^e invention.

Thus, m one embodimeⁿt, oy the addition of boron ana/or zirconium to the iron-based alloy, the format_on of bead-like carbioe films on the grain boundaries can be counteracted or their formation prevented. In addition, by means of the element boron, a lowering of the solidus line, that is to say of the transformation line from "D- to ^-structures, _s achieved, with the result that the material gams further stability and therefore strength.

In a further embodiment, the subassembly according to the invention is distinguished in that the iron-based alloy contains the elements titanium, tantalum and caroon (Ti, Ta, C) with a total fraction of about 5 to 10^ro by weight m relation to the oλ/erall weight of the iron-cased alloy, that is to say of the overall alloy. By means of these elements, t^e precipitation hardness εtno the formation of mtermetallic compounds m the material are increased. In particular, the precipitation hardening achieves a higher nominal strength, so that the material matrix undergoes thermodynamic shrinkage amplitudes which are less plastic t^an elastic. The result is higher oscillatory strength, that is to say a marked increase m bhe resistance of the materia,- under load. Too ^igh a fraction of the elements titanium, ta^tal_^m and carbon, that is to say greater than 10' by weight, reduces the strength of the material again oue to secondary precipitations of carbiαe formations. The elasticity of the material increases again, and therefore a sufficient stab_lity of the workpiece canⁿot be ensured m the lcng term. The structural parts suffer distortion. In the case of a fraction of Ti, Ta ana C of _ess than 5_t by weignt m relation to th^ overall weight of the alloy, the stabi_izi^g fraction of mtermetallic compounds is too low to achieve an improved stability of the workpiece.

In a further emoodiment, the subassembly according to the invention is distinguished m that the iron-oased alloy contains the elements lanthanum and hafnium, their fraction by volαire amounting in total to a maximum of 2i by volume m relation to the overall volume of the overall alloy. By means of such a fraction by volume of the two elements, the ductility of t"e material is once more markedly iⁿcreased. Furthermore, the cohesion and adhesio^ ratios at the grain boundaries and in the matrix are reinforced, so that a break-up of the grain Jooundaries during the casting of the material is prevented even more effectively, or the break-up is markedly reduced. A fraction by volume of more than 2\ by volume of the elements lanthanum and hafnium, moreover, does not afford any renewed marked increase in ductility a^d is therefore not profitaole.

In a further embodiment, the subassembly according to the invention is characterized in that the iron-cased alloy contains the elements _anthanum, hafnium, boron, yttrium and zirconium. As already stated, Y^O₃ is a highly temperature-resistant dispersoid which tends to strong dislocation anchorings and at tπe same time improves the covering layer adhesion, with the result that even the oxidation resistance is iⁿcreased. The element zircoriuir is a_^so a" element effective _^n terms of grain boundaries. It additionally reduces the mtercrystallme grain growth and consequently increases the ductility and the long-terrr rupture strength of the material once more by a multiple. At the same time, zirconium prevents the formation of caroide films on the gram bounαaπes, which may leaα to iⁿstability of tne material and to t^He break-up of the grain boundaries. Surprisingly, then, it was round that, precisely m combination, the elements La, nf, B, Y ana Zr markedly _^ountera_^t the dislocation tendency within the material matrix and thereby increase the strength of the workpiece, a^d therefore the susceptibility of the material to wear is markedly reαuceα. Tnis means trat the structjral parts experience a significant positive ;±ire de._ay in terms cf a break induced by load f_uctuations . Jseful life of the structural oarts can consequently once more joe increased markedly.

In a further embodiment, the subassembly according to the invention for Joyrass control in the turjome casing of a turbocharger is distinguished additionally by an improved hot-gas corrosion performance. This is established, according to the xiiveⁿtioⁿ, via the elements titanium, tantalum, c^hrome and cobalt. In t^κis embodiment, t^eir total fraction amounts to aoout 22 to 35 by weight m relation to the overal- weight of the alloy. In the case of a lower content, that is to say of less than about 22' by we_^g^t, the hot-gas corrosion performance cannot be achieved so we_l. In tne case of a content of more than 35? by weight of the elements specified, there is again a contrary effect ana the hot-gas corrosion performance deteriorates again.

According to a farther emoodiment, the subassembly for bypass control is d-sti^guished by a specif_c composition of the iron-based alloy which contains the following components: C: 0.05 to 0.35% by weight, Cr: 17 to 26% by weight, Ni: 15 to 22% by weight, Co: 15 to 23% by weight, Mo: 1 to A\ by weight, W: 1.5 to 4% by weight, Ta: 1 to 3.5% by weight, Zr: 0.1 to 0.5% by weight, Hf: 0.4 to 1.2% by weight, B: maximum 0.2"- by weight, La: maximum 0.251 by weight, Si: maximum Il by weight, Mn: 1 to 2% by weight, Nb: 0.5 to 2% by weight, Ti: 1 to 2.5% by weight, N: 0.1 to 0.5% by weight, the sum of S and P: less than 0.04^Le by weight, and iron.

The influence of the individual elements on an iron-based alloy is known, but it was surprisingly found, then, that precisely the combination described affords a material which, when processed into a structural part of the subassembly for bypass control in the turbine casing of a turbocharger, gives this a particularly balanced property profile. As a result of this composition according to the invention, a structural part having especially high resistance to the break-up of the grain boundaries during casting is obtained, which, moreover, is distinguished by high strength, while at the same time having very good values for ductility. The soiidus line is markedly lowered. The structural parts are distinguished by a highly positive time delay for an "LCF break", a break under the action of load fluctuations, with the result that the useful life of the structural parts is markedly increased.

Alternatively to this specific composition, the subassembly for bypass control may also be distinguished by the following further specific composition of the iron-based alloy which contains bhe following components: C: 0.05 to 0.35?. by weight, Cr: 17 to 26% by weight, Ni: 15 to 22% by weight, Co: 15 to 23% by weight, Mo: 1 to 4° by weight, W: 1.5 to 4% by weight, Ta: 1 to 3.5% by weight, Zr: 0.1 to 0.5% by weight, Y₂O_^: 0.4 to 1.5% by weight, Ti: 1.5 to 3ό by weight, Si: maximum 1% by weight, Mn: 0.8 to 2.5% by weight, Nb: 0.5 to 1.7% by weight, N: 0.05 to 0.5% by weight, the sum of S and P: less than 0.05% by weight, and iron .

A structural part consisting of an iron-based alloy of this type is also distinguished by the good properties specified above.

Thus, a material which has been produced according to the two specific compositions has the following properties :

According to a further embodiment of the invention, the subassembly according to the invention for bypass control or its iron-based alloy is free of sigma phases. This counteracts the embrittlement of the material and increases its durability. Sigma phases are brittle sintermetallic phases of high hardness. They arise when a body-centered and a face-centered cubic metal, the atomic radii of which are identical with only a slight deviation, meet one another. Such sigma phases are undesirable because of their embrittling εtction and also on account of the property of the matrix to remove chrome. The material according to the invention is distinguished in that it is free of sigma phases. Consequently, the embnttlement of the material is counteracteα ana its durability is increased. The reduction or avoidance of the formatioⁿ of sigma phases is achieved in that the silicor content in the alloy material is lowered to less tⁿan 1.3_O Oy weight and preferably to less than Ic by weig^ht. Furthermore, it is aovantageous to employ austeπite formers, such as, for exanple, manganese, nitrogen and nickel, if appropriate in combination.

According to the invention, the iro^-based alloy, o^ which the subassembly according to the inve"tio" for bypass control m the turbine casing of a turbocharger is based, may be proαuceα by ireans of precision casting cr the MIM method. The respective materials are to be welded by means of conventional VvIG plasma methods ana also EB meτhoαs. Heat treatment takes place by solution annealing at aoout _030 to 1C5O°C for 8 hours _n a vacuum. Precipitation hardening takes place at abo_^t 720⁰C for 16 hours with air -cooling in a Joatch furnace.

Claim 10 defines, as an independently handleable article, an exhaust gas turoocharger which comprises a subassembly for oypass control m the tuicme casing of an exhaust gas turbocharger, as already descrioed, which consists of an iron-based alloy w_th a carb_de microstructure and dispersions of at least one element or one compounα of the "rare earths" and/or Y_ZG3.

Fig. 1 shows a partia_ illustratioⁿ of the turbocharger 1 according to the invention in one embod_ment, wh_ch does not need to be described m any more detail with regard to the compressor, the compressor casing, the compressor shaft, the bearing cas_ng and the bear_ng arrangement and also all other conventional parts. A two-stage exhaust gas inlet dυct cannot be seen here. The exhaust gas inlet duct is provided with a double-flow bypass duct 4 which branches off from the exhaust gas inlet duct and which leads to an exhaust gas outlet 5 of the turbine casing 2. The bypass duct 4 has a regulating flap 6 for opening and closing.

Fig. 2 shows a top view of the flap plate 9 of the regulating flap 6 of the turbocharger 1, the flap plate 9 being circular in this embodiment, although it may, in general, also have flattened regions 11. The flap plate 9 has, furthermore, on its topside an elliptic fastening tenon 10 which is attached eccentrically to the flap plate 9 and on which a fastening head 14 is arranged.

Fig. 3 shows a top view of the fastening lever 8 and the spindle 13 of the regulating flap 6. The fastening lever 8 is fastened to the spindle 13 at a free end 7. The spindle 13 is angularly connected to an actuating member, not illustrated in any more detail, for the actuation of the regulating flap 6. As illustrated in fig. 3, the fastening lever 8 is of plate-shaped design and is oriented at a freely selectable angle Zl (here 130°) to the spindle 13. The fastening lever 8 has, in the region of its free end 15, a reception recess 16, the form of which is elliptic here, so that it corresponds to the elliptic form of the fastening tenon 10 of the flap plate 9.

Fig. 4 shows a top view of the regulating flap 6 composed of the fastening lever 8 and of the flap plate 9. Fig. 4 illustrates the mounted regulating flap 6 in which the fastening tenon 10 is arranged in the reception recess 16 and the arrangement is fixed by means of the fastening head 14. Furthermore, fig. 4 illustrates the position of the ducts of the double-flow bypass duct 4 by means of the two dashed semicircles 17 and 18, these two ducts 17 and 18 being separated by means of the partition 19. Moreover, the center of the first duct 17 is indicated by the point Ml and the center of the second duct 18 by the point M2. The line M₁ designates the center of the fastening head 14, and the dimensions A and B indicate the lever arms resulting from the geometric arrangement of the flap plate 9 with eccentric mounting on the fastening lever 8.

List of reference symbols

1 Turbocharger

2 Turbine casing

4 Bypass duct

5 Exhaust gas outlet

6 Regulating flaρ/wastegate flap

7 Free end of the spindle 13

8 Fastening lever

9 Flap plate

10 Fastening tenon of the flap plate 9

11 Flattened region of the flap plate 9

13 Spindle

14 Fastening head

15 Free end of the bypass lever 8

16 Reception recess

17 First duct of the bypass duct

18 Second duct of the bypass duct

19 Partition M1,M2 Centers

M₁₁ Center of the fastening head

A, B Lever arms

L Longitudinal axis of the fastening lever 8

Zl Angle between the spindle 13 and L

Claims

PATENT CLAIMS

1. A suoassembly for bypass control m the turb_ne 5 casing of a turbocharger, in particular for a diesel engine, consisting of an iron-based alloy with a caroide microstruct_^re ana dispersions of at least one element or one compound of t^He "rare earths" and/or

Y,C,. 0

2. The suoassemoly for oypass control as claimed in claim 1, wherein the iron-based alloy conta_ns further elements, such as boron and/or zirconium. 5

3. The suoassembly for bypass control as claimed in claim 1 or 2, wherein the _^ron-baseα alloy contains the elements titaⁿium, tantalum and carbon, their total fraction amounting to about 5 to 10°_o Joy weight m relation to the overall alloy. 0

4. The subassemoly for oypass control as claimed in one of the preceding claims, w^herein tne iron-based alloy contains the elements lanthanum and hafnium, their fraction by volume amounting m total to a5 maximum of about 2\ by vol_^ire in relation tc the overall volume of the alloy.

5. The suoassembly for bypass control as claimed m one of the preceding claims, wherein the iron-basedC alloy contains the elements lanthanum, hafnium, boron, yttrium and zirconium.

6. The suoassembly for bypass control as claimed m one of the preceding claims, wherein t^e iro^-based5 alloy contains the elements cobalt, chrome, titanium ana tantalum, their total fraction amounting to about 22 to 35 o by weight m relation to the overall alloy.

7. The suioassembly for bypass control as claimed in one of the preceding claims, wherein the iron-based alloy contains the following components: C: 0.05 to 0.35% by weight, Cr: 17 to 261 by weight, Ni: 15 to 22°, by weight, Co: 15 to 23% by weight, Mo: 1 to 4% by weight, W: 1.5 to 4 O by weight, Ta: 1 to 3.51 by weight, Zr: 0.1 to 0.5% by weight, Hf: 0.4 to 1.21 by weight, B: maximum 0.2% by weight, La: maximum 0.25% by weight, Si: maximum 1° by weight, Mn: 1 to 2% by weight, Nb: 0.5 to 2? by weight, Ti: 1 to 2.5% by weight, N: 0.1 to 0.5^rc by weight, the sum of S and P: less than 0.04% by weight, and Fe.

8. The subassembly for bypass control as claimed in one of the preceding claims 1 to 6, wherein the iron-based alloy contains the following components: C: 0.05 to 0.35 o by weight, Cr: 17 to 26% by weight, Ni: 15 to 22% by weight, Co: 15 to 23% by weight, Mo: 1 to 4% by weight, W: 1.5 to 4% by weight, Ta: 1 to 3.5% by weight, Zr: 0.1 to 0.5% by weight, Y^O,: 0.4 to 1.5% by weight, Ti: 1.5 to 3% by weight, Si: maximum 1° by weight, Mn: 0.8 to 2.5% by weight, Nb: 0.5 to 1.7i by weight, N: 0.05 to 0.5% by weight, the sum of S and P: less than 0.05% by weight, and Fe.

9. The subassembly for bypass control as claimed in one of the preceding claims, wherein the iron-based alloy is free of sigma phases.

10. An exhaust gas turbocharger, in particular for diesel engines, comprising a subassembiy for bypass control in the turbine casing of the turbocharger, consisting of an iron-based alloy with a carbide microstructure and dispersions of at least one element or one compound of the "rare earths" and/or Y^Ch.

11. The exhaust gas turbocharger as claimed in claim 10, wherein the iron-based alloy contains further elements, such as boron and/or zirconium.

12. The exhaust gas turbocharger as claimed in claim 1 or 2, wherein the iron-based alloy contains the elements titanium, tantalum and carbon, their total fraction amounting to about 5 to 10^f? by weight in relation to the overall alloy.

13. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 12, wherein the iron-based alloy contains the elements lanthanum and hafnium, their fraction by volume amounting in total to a maximum of about 2 \ by volume in relation to the overall volume of the alloy.

14. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 13, wherein the iron-based alloy contains the elements lanthanum, hafnium, boron, yttrium and zirconium.

15. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 14, wherein the iron-based alloy contains the elements cobalt, chrome, titanium and tantalum, their total fraction amounting to about 22 to 35^rό by weight in relation to the overall alloy.

16. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 15, wherein the iron-based alloy contains the following components: C: 0.05 to 0.35^f5 by weight, Cr: 17 to 2Ot by weight, Ni: 15 to 22i> by weight, Co: 15 to 2Υ% by weight, Mo: 1 to 4% by weight, W: 1.5 to 4o by weight, Ta: 1 to 3.5-? by weight, Zr: 0.1 to 0.5 J. by weight, Hf: 0.4 to 1.2° by weight, B: maximum 0.2^rc by weight, La: maximum 0.25% by weight, Si: maximum 1% by weight, Mn: 1 to 2% by weight, Nb: 0.5 to 2% by weight, Ti: 1 to 2.5% by weight, N: 0.1 to 0.5¹T. by weight, the sum of S and P: less than 0.04% by weight, and Fe.

17. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 15, wherein the iron-based alloy contains the following components: C: 0.05 to 0.35% by weight, Cr: 17 to 26% by weight, Ni: 15 to 22% by weight, Co: 15 to 23% by weight, Mo: 1 to 4% by weight, W: 1.5 to 4% by weight, Ta: 1 to 3.5% by weight, Zr: 0.1 to 0.5% by weight, Y^: 0.4 to 1.5% by weight, Ti: 1.5 to 3% by weight, Si: maximum 1% by weight, Mn: 0.3 to 2.5% by weight, Nb: 0.5 to 1.7% by weight, N: 0.05 to 0.5% by weight, the sum of S and P: less than 0.05c. by weight, and Fe.

18. The exhaust gas turbocharger as claimed in one of the preceding claims 10 to 17, wherein the iron-based alloy is free of sigma phases.