Rolling bearing

Abstract

The invention aims to provide a rolling bearing that secures a sufficient bearing life economically even when used under such conditions that water from the outside or water formed by moisture condensation may seep into the lubricant or the bearing is affected by the vibrations, and particularly a rolling bearing suited to the electric parts and accessaries of au automobile engine, such as an alternator. To accomplish the object, the hydrogen ion exponent pH of the grease sealed into the inside of the bearing is adjusted in a range of from 7 to 13. For the same purpose, the hydrogen ion exponent pH of the grease is adjusted in a range of from 5 to 13 where a prescribed amount of an organic metal salt or ADTC is added to the grease, where a prescribed amount of an inorganic compound having an average particle size of 2 □m or smaller is added to the grease, or where a diurea compound containing an aromatic amine or a mixture of the diurea compound is added to the grease as a thickener.

What is claimed is:  
     
         1 . A rolling bearing having outer and inner races and rolling elements which are rotatably put in between the outer and inner races, with a lubricant sealed into the annular space formed by the rolling elements and the races, which is characterized in that said lubricant comprises a base oil, a thickener, and a pH adjustor and has its hydrogen ion exponent pH adjusted in a range of from 7 to 13.  
     
     
         2 . A rolling bearing according to  claim 1 , characterized in that said base oil has a dynamic viscosity of 40 to 400 mm 2 /sec at 40° C. and comprises an oil selected from any one of mineral oils, synthetic oils, and natural oils.  
     
     
         3 . A rolling bearing according to  claim 1 , characterized in that said thickener is selected from at least one of a metal soap, a complex metal soap, and a urea compound.  
     
     
         4 . A rolling bearing according to  claim 3 , characterized in that said urea compound is a diurea compound comprised of an amine residue selected from at least one of a cyclohexyl group, a C n  (n=7 to 12) alkylcyclohexyl group, a C n  (n=8 to 20) straight-chain alkyl group and an isocyanate residue comprising a divalent C n  (n=6 to 15) aromatic ring-containing hydrocarbon group.  
     
     
         5 . A rolling bearing according to  claim 1 , characterized in that said pH adjustor is an alkaline substance selected from at least one of an amine compound, an organic metal salt, an organic acid metal salt, and an alkaline inorganic compound.  
     
     
         6 . A rolling bearing according to  claim 5 , characterized in that said amine compound is at least one of primary to tertiary amine compounds containing an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group, which each has carbon atoms C n  (n=1 to 24), or a derivative thereof.  
     
     
         7 . A rolling bearing according to  claim 5 , characterized in that said organic metal salt or organic acid metal salt as a pH adjustor has a C n  hydrocarbon chain (n=6 to 24) which constitutes the alkyl group and a metal element, which constitutes the metal salt, selected from at least one of an alkali metal, an alkaline earth metal, aluminum and zinc.  
     
     
         8 . A rolling bearing according to  claim 5 , characterized in that said alkaline inorganic compound is selected from at least one of a metal hydroxide, a metal carbonate, a metal borate, and a metal silicate.  
     
     
         9 . A rolling bearing having outer and inner races and rolling elements which are rotatably put in between the outer and inner races, with a lubricant sealed into the annular space formed by the rolling elements and the races, which is characterized in that said lubricant comprises a base oil, a thickener, a pH adjustor, and a reaction film forming agent capable of forming a reaction film on the raceway surface or the rolling surface which is selected from at least one of an organic metal salt and an ash-free dialkyldithiocarbamic acid and has its hydrogen ion exponent pH adjusted in a range of from 5 to 13.  
     
     
         10 . A rolling bearing according to  claim 9 , characterized in that said organic metal salt as a reaction film forming agent is selected from at least one of a dialkyldithiocarbamic acid compound, a dialkyldithiophosphoric acid compound, an organozinc compound, and a zinc alkylxanthogenate or a methylenebisdialkyl-dithiocarbamic acid.  
     
     
         11 . A rolling bearing having outer and inner races and rolling elements which are rotatably put in between the outer and inner races, with a lubricant sealed into the annular space formed by the rolling elements and the races, which is characterized in that said lubricant comprises a base oil, a thickener, a pH adjustor, and 0.001 to 3 wt % of particles comprising an inorganic compound having an average particle size of 2 μm or smaller and has its hydrogen ion exponent pH adjusted in a range of from 5 to 13.  
     
     
         12 . A rolling bearing according to  claim 11 , characterized in that said inorganic compound is selected from at least one of a metal oxide, a metal hydroxide, a metal carbonate, or a hydrate thereof; a metal nitride; a metal carbide; a clay mineral; diamond; and a solid lubricant.  
     
     
         13 . A rolling bearing having outer and inner races and rolling elements which are rotatably put in between the outer and inner races, with a lubricant sealed into the annular space formed by the rolling elements and the races, which is characterized in that said lubricant comprises a base oil, a pH adjustor, and a thickener selected from at least one of an aromatic diurea compound and a non-aromatic diurea compound and that said lubricant has its hydrogen ion exponent pH adjusted in a range of from 5 to 13.  
     
     
         14 . A rolling bearing according to  claim 13 , characterized in that the aromatic amine residue contained in said aromatic diurea compound is a C n  (n=7 to 12) aromatic ring-containing hydrocarbon group.  
     
     
         15 . A rolling bearing according to  claim 13 , characterized in that the non-aromatic amine residue contained in said aromatic diurea compound and said non-aromatic diurea compound comprises at least one of a cyclohexyl group, a C n  (n=7 to 12) alkylcyclohexyl group, and a C n  (n=-8 to 20) straight-chain alkyl group and that the diisocyanate residue is a divalent C n  (n=6 to 15) aromatic ring-containing hydrocarbon group.  
     
     
         16 . A rolling bearing according to  claim 13 , characterized in that the aromatic amine residue and the non-aromatic amine residue contained in said aromatic diurea compound and said non-aromatic diurea compound are in the following relationship:  
       Molar ratio of aromatic amine residue/(molar ratio of aromatic amine residue+molar ratio of the non-aromatic amine residue)=0.5 to 0.95  
     
     
         17 . A rolling bearing according to  claim 13 , characterized in that the content of said thickener in the lubricant is 8 to 35 wt %.