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EP-4739758-A1 - GREASE COMPOSITION FOR BEARINGS OF RAIL VEHICLES

EP4739758A1EP 4739758 A1EP4739758 A1EP 4739758A1EP-4739758-A1

Abstract

The present invention relates to a grease composition for bearings of rail vehicles, in particular rail wheel bearings and traction motor bearings of rail vehicles. The invention further relates to rail wheel bearings and traction motor bearings comprising said grease composition and the use of the grease composition for grease lubrication of rail wheel bearings and traction motor bearings.

Inventors

  • FIEDLER, FRANK
  • ROSENHEINRICH, BERT
  • PAUSCH, MICHAEL
  • ROBERT, Jan
  • SEGEDI-DROBNJIK, Marijana
  • SCHMIDT-AMELUNXEN, MARTIN

Assignees

  • Schaeffler Technologies AG & Co. KG
  • Klüber Lubrication GmbH & Co. KG

Dates

Publication Date
20260513
Application Date
20240703

Claims (20)

  1. 1 . The use of a grease composition, comprising a) a base oil mixture, comprising a1) at least one polyalphaolefin, and a2) at least one poly(alkylene)glycol, b) at least one lithium complex soap, and c) at least one ionic liquid, for grease lubrication of rail wheel bearings and traction motor bearings of rail vehicles.
  2. 2. The use of a grease composition, comprising a) a base oil mixture, comprising a1) at least one polyalphaolefin, and a2) at least one poly(alkylene)glycol, wherein components a1) and a2) are immiscible or only partly miscible, b) at least one lithium complex soap, and c) at least one ionic liquid, for grease lubrication of rail wheel bearings and traction motor bearings of rail vehicles.
  3. 3. The use according to claim 1 or 2, wherein components a1) and a2) are immiscible at 20°C.
  4. 4. The use according to any of the preceding claims, wherein the poly(alkylene)glycol a2) is selected from ethylene oxide/propylene oxide copolymers, propylene oxide homopolymers and mixtures thereof, preferably the poly(alkylene)glycol a2) is selected from propylene oxide homopolymers.
  5. 5. The use according to any of the preceding claims , wherein the polyalphaolefin a1) (PAO) and the poly(alkylene)glycol a2) (PAG) have a distance Ra between the Hansen Solubility Parameters, calculated by the formula Ra = {4(5d(PAG) - 6d(PAO)) 2 +(6p(PAG) - 6p(PAO)) 2 +(6h(PAG) - 6h(PAO)) 2 } 0 ' 5 of at least 9.5 (J/cm 3 ) 05 , more preferably of at least 10.0 (J/cm 3 ) 05 .
  6. 6. The use according to any of the preceding claims, wherein the grease composition additionally comprises at least one additive (component d), especially selected from thickeners different from component b), corrosion inhibitors, antioxidants, metal deactivators, organic or inorganic solid lubricants, viscosity index improvers, anti-wear additives, radical scavengers, UV stabilisers, pour point depressing additives, friction modifiers, dispersing active compounds, and mixtures thereof.
  7. 7. The use according to any of the preceding claims, wherein the grease composition additionally comprises at least one base oil (component a3) different from a1 ) and a2), preferably selected from: ester oils, preferably selected from aromatic ester oils, like trimellitates, hemimellitates, pyromellitates; polyol ester oils, preferably pentaerythritol esters, dipentaerythritol esters, trimethylolpropane esters and neopentylglycol esters; estolides; dimer fatty acid esters; further dimeric and trimeric acid esters; carbonate ester oils; ether oils, preferably selected from diaryl ethers, triaryl ethers, alkyldiphenyl ether, polyphenyl ethers, linear or branched perfluoro polyether oils (PFPE oils); mineral oils; synthetic hydrocarbons different from a1 ), preferably polybutenes, polyisobutenes and copolymers of alphaolefins with at least one comonomer; alkylnaphthalene oils; alkylbenzene oils; natural fats and oils; phosphate ester oils; silicon oils; fluorinated oils; and mixtures thereof.
  8. 8. The use according to any of the preceding claims, wherein the grease composition comprises from 40.0 to 95.0 % by weight, preferably from 50.0 to 90.0 % by weight, in particular from 60.0 to 85.0 % by weight, based on the total weight of the composition, of at least one base oil mixture a).
  9. 9. The use according to any of the preceding claims, wherein the grease composition comprises at least 20.0 % by weight, preferably at least 25.0 % by weight, based on the total weight of the composition, of at least one polyalphaolefin a1 ).
  10. 10. The use according to any of the preceding claims, wherein the grease composition comprises at least 20.0 % by weight, preferably at least 25.0 % by weight, based on the total weight of the composition, of at least one poly(alkylene)glycol a2).
  11. 1 1 . The use according to any of the preceding claims, wherein the weight ratio of component a1 ) to component a2) is in a range of 99.0 : 1 .0 to 1 .0 : 99.0, preferably 10 : 90 to 90 : 10, in particular 70 : 30 to 30 : 70 .
  12. 12. The use according to any of the preceding claims, wherein the grease composition comprises 0 to 50.0 % by weight, especially 3.0 to 25.0 % by weight, more especially 10.0 to 20.0 % by weight, based on the total weight of the composition, of at least one base oil a3).
  13. 13. The use according to any of the preceding claims, wherein the grease composition comprises 4.0 to 25.0 % by weight, especially 6.0 to 23.0 % by weight, more especially 10.0 to 20.0 % by weight, based on the total weight of the composition, of at least one lithium complex soap b).
  14. 14. The use according to any of the preceding claims, wherein the ionic liquid c) comprises at least one anion, selected from bis(perfluoroalkylsulfonyl)imides, bis(fluorosulfonyl)imide, tris(perfluoroalkylsulfonyl)methides, tris(perfluoroalkyl)trifluorophosphates and mixtures thereof, preferably selected from bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide and mixtures thereof.
  15. 15. The use according to any of the preceding claims, wherein the ionic liquid c) comprises at least one cation, selected from symmetrical and asymmetrical ammonium ions, NR1R2R3RT and phosphonium ions PRI R2RS 4 + , wherein the radicals R1 to R4 are each independently of one another branched or unbranched, unsubstituted or substituted Ci to C24 alkyl groups or unsubstituted or substituted C& to C30 aryl groups.
  16. 16. The use according to any of the preceding claims, wherein the ionic liquid c) is selected from (trihexyl(tetradecyl)phosphonium) bis(trifluoromethylsulfonyl)imide, (tributyl(tetradecyl)phosphonium) bis(trifluoromethylsulfonyl)imide, (tetraoctylphosphonium) bis(trifluoromethylsulfonyl)imide, (methyltrioctylammonium) bis(trifluoromethylsulfonyl)imide, trihexyl(tetradecyl)phosphonium) bis(fluorosulfonyl)imide, (tributyl(tetradecyl)phosphonium) bis(fluorosulfonyl)imide, (tetraoctylphosphonium) bis(fluorosulfonyl)imide, (methyltrioctylammonium) bis(fluorosulfonyl)imide and mixtures thereof.
  17. 17. The use according to any of the preceding claims, wherein the grease composition comprises 0.1 to 10.0 % by weight, preferably 0.2 to 5.0 % by weight, in particular 0.5 to 2.0 % by weight, based on the total weight of the composition, of at least one ionic liquid c).
  18. 18. The use according to any of the preceding claims, wherein the grease composition comprises: a1 ) 20 to 77.9 % by weight, based on the total weight of the composition, of at least one polyalphaolefin, a2) 20 to 77.9 % by weight, based on the total weight of the composition, of at least one poly(alkylene)glycol, a3) 0 to 50.0 % by weight, based on the total weight of the composition, of at least one base oil different from a1) and a2), b) 2.0 to 25.0 % by weight, based on the total weight of the composition, of at least one lithium complex soap, c) 0.1 % to 10.0 % by weight, based on the total weight of the composition, of at least one ionic liquid, d) 0 % to 20.0 % by weight, based on the total weight of the composition, of at least one additive, especially selected from thickeners different from component b), corrosion inhibitors, antioxidants, metal deactivators, organic or inorganic solid lubricants, viscosity index improvers, anti-wear additives, radical scavengers, UV stabilisers, pour point depressing additives, friction modifiers, extreme pressure additives, dispersing active compounds, and mixtures thereof.
  19. 19. The use according to any of the preceding claims for improving at least one property selected from increasing the service life of rail wheel bearings and traction motor bearings, increasing the range of possible operating temperatures in the rail wheel bearings, in particular increasing the upper operating temperature, increasing the speed parameter range of the rail wheel bearings, in particular increasing the upper speed limit of the bearings, reducing the noise emission of rail wheel bearings, increasing the electrical conductivity.
  20. 20. A rail wheel bearing, contained in a wheel arrangement for a rail vehicle, comprising a grease composition as defined in any of claims 1 to 18.

Description

Grease composition for bearings of rail vehicles SUBJECT MATTER OF THE INVENTION The present invention relates to a grease composition for bearings of rail vehicles, in particular rail wheel bearings and traction motor bearings of rail vehicles. The invention further relates to rail wheel bearings and traction motor bearings comprising said grease composition and the use of the grease composition for grease lubrication of rail wheel bearings and traction motor bearings. BACKGROUND OF THE INVENTION In the field of rail mobility, wheel bearings are used millions of times and are one of the critical components, which require a strict maintenance schedule. Axle bearings (axlebox bearings) are an essential design element in the bogies and chassis on all railway vehicles that connect the wheelset to the non-rotating parts of the rail vehicle and must transmit the weight of the vehicle to the wheelsets while providing a smooth rolling movement for the wheelsets. Rolling stock axle bearings are subject to radial impact loads caused e.g., by rail joints and switches, as well as to the static and dynamic radial loads of vehicle weight. Axial loads can be caused by lateral movements e.g., when trains run on curved rails. The combination of significant relative movements and high forces creates the risk for wear. Recent rolling stock are therefore equipped with greased rail wheel bearings, which require monitoring and maintenance. Once a damage process is initiated, it tends to accelerate, as the pre-damaged bearing is source for local vibrations and heat, which both represent additional loads, and subsequently a source for damage increase. Also, the bearings used in the traction motors of e.g., electric locomotives are exposed to high mechanical stresses. Today's traction motor bearings must possess excellent highspeed and heavy-load capabilities. One important factor especially in the development of maintenance free traction motor bearings is to prevent electric pitting. An important instrument for reducing the operating costs of rail vehicles is the extension of maintenance intervals. A key influencing factor for increasing the service life of rail wheel bearings is the service life of the grease used for lubrication. The lubricant compositions used to lubricate railway wheel bearings are subjected to severe operating conditions, with the afore-mentioned high mechanical stress on the wheel bearings, as well as high maximum operating temperatures and large temperature differences, high running speeds, long operating times, dust, humidity, and discharges of electric current, etc. The need for regular replacement of lubricants is a major obstacle to maintenance-free operation. Axle bearings are in particular selected from cylindrical roller bearings, tapered roller bearings and spherical roller bearings. Actual axle bearings can be classified into the following six types based both on bearing type and sealing device: RCT Bearings (Sealed-Clean Rotating End Cap Tapered Roller Bearings), RCC Bearings (Sealed-Clean Rotating End Cap Cylindrical Roller Bearings), Spherical roller bearings, Cylindrical roller bearings combined with ball bearings, Cylindrical roller bearings with ribs, Tapered roller bearings. CN 109135886 A describes a lubricating grease composition for rolling bearings of highspeed trains reaching speeds of 250-350 km/h. The lubricating grease composition comprises a base oil, comprising 30 - 38 wt.% mineral oil, 60 - 65 wt.% synthetic oil and 2 - 5 wt.% ester oil with a viscosity of the base oil mixture in the range of 10 - 60 mm2/s at 40°C. The base oil is thickened with a mixture of lithium soaps, comprising lithium stearate soap, lithium 12-hydroxystearate soap and hydrogenated castor oil lithium soap. Further additives are antioxidants, anti-wearing agents, rust preventive agents and ZnO as structure improving agent. CN 106867633 A describes a high-speed railway shaft box double-row tapered roller bearing lubricating grease composition, comprising 50 - 83 wt.% of a base oil mixture, 8 - 25 wt.% thickener and 6 - 25 wt.% further additives. The base oil comprises an 1 : 1 mixture of an ester oil and a synthetic oil with a viscosity of the base oil mixture in the range of 40 - 80 mm2/s at 40°C and a pour point of -65°C. The thickening agent comprises lithium soaps of 12-hydroxystearic acid, heptanoic acid and myristic acid. Further additives are calcium sulfonate, extreme pressure agents, antirust agents, repairing agents and antioxidants. An example of a repairing agent is a mixture of nano copper oxide and nano zinc oxide. JP 2014108999 A (JP 5988376 B2) describes a grease composition for a main electric motor shaft bearing of a railway vehicle, which has excellent heat resistance and a long bearing lubrication life. The grease composition comprises a thickener including a hydroxy fatty acid with a carbon number of 12 to 24 having one or a plurality of hydroxyl groups and a lithium salt of a fatty ac