Grease composition and rolling bearing

Abstract

A grease composition containing base oil, a thickener, and an additive, wherein said additive contains at least one kind selected from among a phosphite ester shown by a chemical formula (1) or a phosphite ester shown by a chemical formula (2); a content of said phosphite ester is 0.5 to 4 parts by weight for 100 parts by weight which is a total of an amount of said base oil and that of said thickener; and said additive contains neither phosphite esters other than said phosphite ester shown by said formula (1) or by said formula (2) nor phosphate esters having organic groups whose carbon number is not less than three:

1 - 14 . (canceled) 
     
     
         15 . A rolling bearing, which supports a rotor of a motor, said rolling bearing comprising an inner ring; an outer ring; a plurality of rolling elements disposed between said inner ring and said outer ring; a sealing member provided at openings disposed at both axial ends of said inner ring and said outer ring; and
 a grease composition being in circumferences of said rolling elements,   wherein said grease composition is a grease composition containing base oil, a thickener, and an additive,   wherein said base oil has a kinematic viscosity at 40° C. of 20 to 50 mm 2 /s,   wherein said additive contains at least one kind selected from the group consisting of a phosphite ester of chemical formula (1) and a phosphite ester of chemical formula (2); wherein a content of said phosphite ester is 0.5 to 4 parts by weight for 100 parts by weight which is a total of an amount of said base oil and that of said thickener;   said phosphite ester is dimethyl phosphite, diethyl phosphite, trimethyl phosphite or triethyl phosphite; and   said additive contains neither phosphite esters other than said phosphite ester shown by said formula (1) or by said formula (2) nor phosphate esters having organic groups whose carbon number is not less than three:   
       
         
           
           
               
               
           
         
         in chemical formulas (1) and (2), R 1 , R 2 , R 3 , R 4 , and R 5  denote a methyl group or an ethyl group; R 1  and R 2  are the same group or different groups; R 3 , R 4 , and R 5  are the same group or different groups. 
       
     
     
         16 . A rolling bearing according to  claim 15 , wherein said base oil is at least one selected from among ester oil and poly-α-olefin oil. 
     
     
         17 . A rolling bearing according to  claim 16 , wherein said base oil is said ester oil or a mixed oil of said ester oil and said poly-α-olefin oil. 
     
     
         18 . A rolling bearing according to  claim 15 , wherein a content of said thickener which occupies in 100 parts by weight of a total amount of said base oil and said thickener is 5 to 30 parts by weight. 
     
     
         19 . A rolling bearing according to  claim 15 , wherein said thickener is at least one selected from among lithium soap and a urea compound. 
     
     
         20 . A rolling bearing according to  claim 15 , which is a deep groove ball bearing. 
     
     
         21 . A rolling bearing according to  claim 15 , which supports rotors of motors for industrial machines and electric equipments and rotors of motors for driving electric cars. 
     
     
         22 . A rolling bearing, comprising an inner ring; an outer ring; a plurality of rolling elements interposed between said inner ring and said outer ring; and
 a grease composition being packed in circumferences of said rolling elements,   wherein said grease composition is a grease composition containing base oil, a thickener, and an additive,   wherein said additive contains at least one kind selected from the group consisting of a phosphite ester of chemical formula (1) and a phosphite ester of chemical formula (2); wherein a content of said phosphite ester is 0.5 to 4 parts by weight for 100 parts by weight which is a total of an amount of said base oil and that of said thickener;   said phosphite ester is dimethyl phosphite, diethyl phosphite, trimethyl phosphite or triethyl phosphite; and   said additive contains neither phosphite esters other than said phosphite ester shown by said formula (1) or by said formula (2) nor phosphate esters having organic groups whose carbon number is not less than three:   
       
         
           
           
               
               
           
         
         In chemical formulas (1) and (2), R 1 , R 2 , R 3 , R 4 , and R 5  denote a methyl group or an ethyl group; R 1  and R 2  are the same group or different groups; R 3 , R 4 , and R 5  are the same group or different groups. 
       
     
     
         23 . A rolling bearing according to  claim 22 , wherein said rolling bearing is used as a hub bearing. 
     
     
         24 . A rolling bearing according to  claim 23 , wherein
 carbon steel for machine structural use is used as a material in said hub bearing.   
     
     
         25 . A rolling bearing according to  claim 23 , wherein said thickener is a urea compound shown by a chemical formula (3): 
       
         
           
           
               
               
           
         
         in chemical formula (3), R 7  denotes a divalent hydrocarbon group whose carbon number is 6 to 15, each of R 6  and R 8  denotes a monovalent aromatic hydrocarbon group and R 6  and R 8  are the same or different. 
       
     
     
         26 . A rolling bearing according to  claim 23 , wherein said base oil is a mineral oil, and a kinematic viscosity of said base oil at 40° C. is 20 to 150 mm 2 /s. 
     
     
         27 . A rolling bearing according to  claim 23 , wherein a content of said thickener which occupies in 100 parts by weight of a total amount of said base oil and said thickener is 5 to 30 parts by weight. 
     
     
         28 . A rolling bearing according to  claim 23 , wherein a worked penetration of said grease composition is 200 to 350.