Bearing grease

Abstract

A bearing grease contains a base oil and a thickener. The base oil is a base oil mixture containing a polyalphaolefin and an ester. The bearing grease is used in an atmosphere of a fluorine compound refrigerant containing no hydrogen. A bearing using the bearing grease does not cause elution of grease for a long time. Further, since there is no need for a collecting system unlike lubricating oil, the arrangement around the bearing can be made compact. Thus, the bearing can be easily applied in a form of an energy recovery equipment to a vehicle or various industrial machineries.

1 - 10 . (canceled) 
     
     
         11 . A method, comprising:
 lubricating a bearing using a grease, the grease comprising:   a base oil; and   a thickener, wherein   the base oil is a base oil mixture comprising a polyalphaolefin and an aromatic ester, a mass ratio of the polyalphaolefin to the aromatic ester is in a range from 50:50 to 93:7, and the thickener is a urea thickener represented by the following formula (1),
   R 1 NHCONHR 2 NHCONHR 3    (1)
 
   where R 1  and R 3  respectively independently represent: a monovalent linear hydrocarbon group having 6 to 22 carbon atoms; a monovalent alicyclic hydrocarbon group having 6 to 12 carbon atoms; or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and   R 2  represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, the bearing grease being used in an atmosphere of a fluorine compound refrigerant containing no hydrogen.   
     
     
         12 . The method according to  claim 11 , wherein 10 mass % or more of the hydrocarbon groups represented by R1 and R3 is occupied by a monovalent alicyclic hydrocarbon group having 6 to 12 carbon atoms. 
     
     
         13 . The method according to  claim 11 , wherein a worked penetration of the grease is in a range from 200 to 380. 
     
     
         14 . The method according to  claim 11 , wherein the fluorine compound refrigerant is at least
 one of CF 3 CF 2 C(O)CF(CF 3 ) 2  and CF 3 —(OC(CF 3 )FCF 2 )m-(OCF 2 )n-OCF 3 .   
     
     
         15 . The method according to  claim 14 , wherein the fluorine compound refrigerant is CF 3 CF 2 C(O)CF(CF 3 ) 2 . 
     
     
         16 . The method according to  claim 11 , wherein the bearing is used in a Rankine cycle. 
     
     
         17 . The method according to  claim 16 , wherein the bearing is used in a turbo Rankine cycle.