Bi-directional tapered roller bearing assembly with improved wear resistance

Abstract

The wear resistance of a bi-directional tapered roller bearing is improved by applying a tribological coating to both the small and large end faces of the roller and to at least one of the rib faces of the bearing assembly.

1 . A bi-directional tapered roller bearing comprising a tapered inner raceway, a tapered outer raceway facing the tapered inner raceway, and a plurality of tapered rollers positioned between the tapered inner and outer raceways; the tapered rollers having a side surface, a large end face at a large diameter end of the tapered roller and a small end face at a small diameter end of the tapered roller; the bearing including a first rib at one of an axial inner or outer edge of said inner raceway and a second rib at the other of the axial inner and outer edges of said outer raceway, said first and second ribs each defining a rib face; one of said rib faces being adjacent the large end of said tapered roller and the other rib being adjacent the small end of the tapered roller; the bearing further including a tribological coating applied to both the large end and the small end of the tapered roller and to at least one of the first and second rib faces; the coating being an amorphous carbon-based or hydrocarbon-based thin film coating. 
     
     
         2 . The bearing of  claim 1  wherein the tribological coating is on both said first rib face and said second rib face. 
     
     
         3 . The bearing of  claim 1  wherein said coating has a thickness of less than 10 μm. 
     
     
         4 . The bearing of  claim 1  wherein said coating has a hardness equal to or greater than the hardness of the substrate to which it is applied. 
     
     
         5 . The bearing of  claim 4  wherein the coating has a hardness of at least about 9 GPa as measured by nanoindentation with a Berkovich diamond indenter. 
     
     
         6 . The bearing of  claim 1  wherein the coating comprises an adhesion layer applied to the surface to be coated and a top functional layer about the adhesion layer; the functional layer being a hard carbonaceous layer. 
     
     
         7 . The bearing of  claim 6  wherein the adhesion layer is chosen from the group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), nickel (Ni), molybdenum (Mo), iron (Fe) or silicon (Si); the adhesion layer as pure as possible in the dominant element. 
     
     
         8 . The bearing of  claim 6  wherein one or more additives are present in the carbonaceous top layer; the additives being chosen from the group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), nickel (Ni), molybdenum (Mo), iron (Fe), silicon (Si), tungsten (W), vanadium (V), niobium (Nb), zirconium (Zr), oxygen (O), nitrogen (N), boron (B), fluoride (F), carbidic inclusions and combinations thereof; the additives comprising 50 atomic % or less of the total top layer composition, the balance of top layer composition being carbon and hydrogen. 
     
     
         9 . The bearing of  claim 6  wherein the carbonaceous functional top layer has no additives and consists of only amorphous carbon (C) or hydrocarbon (C and H). 
     
     
         10 . A bi-directional tapered roller bearing comprising:
 a tapered inner raceway;   a tapered outer raceway facing the tapered inner raceway;   a plurality of tapered rollers positioned between the tapered inner raceway and the tapered outer raceway, the tapered rollers having a side surface, a large end face at a large diameter end of the tapered roller and a small end face at a small diameter end of the tapered roller;   a first rib at an axial outer edge of the inner raceway;   a second rib at an axial inner edge of the inner raceway;   a third rib at an axial outer edge of the outer raceway, the first rib, the second rib and the third rib respectively define a first rib face, a second rib face and a third rib face, the first and third rib faces being adjacent the large end of the tapered roller and the second rib face being adjacent the small end of the tapered roller; and   a tribological coating applied to both the large end and the small end of the tapered roller and to one or more of the first rib face, the second rib face and the third rib face, the coating being an amorphous carbon-based or hydrocarbon-based thin film coating that is non-adhesive to metallic debris particles within the bearing such that the coating prevents wear of the roller ends and the respective one or more of the first rib face, the second rib face and the third rib face caused by the metallic debris particles.   
     
     
         11 . The bearing of  claim 10  wherein the tribological coating is on both said first rib face and said second rib face. 
     
     
         12 . The bearing of  claim 10  wherein said coating has a thickness of less than 10 μm. 
     
     
         13 . The bearing of  claim 10  wherein said coating has a hardness equal to or greater than the hardness of a substrate to which it is applied. 
     
     
         14 . The bearing of  claim 13  wherein the coating has a hardness of at least about 9 GPa as measured by nanoindentation with a Berkovich diamond indenter. 
     
     
         15 . The bearing of  claim 10  wherein the coating comprises an adhesion layer applied to the surface to be coated and a top functional layer over the adhesion layer; the functional layer being a carbonaceous layer. 
     
     
         16 . The bearing of  claim 15  wherein the adhesion layer is chosen from the group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), nickel (Ni), molybdenum (Mo), iron (Fe) or silicon (Si). 
     
     
         17 . The bearing of  claim 15  wherein the adhesion layer includes low levels carbon (C), hydrogen (H), oxygen (O) and combinations thereof, the amount of C, H and/or O in the adhesion layer not exceeding about  75  atomic % of the adhesion layer. 
     
     
         18 . The bearing of  claim 15  wherein one or more additives are present in the carbonaceous top layer; the additives being chosen from the group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), nickel (Ni), molybdenum (Mo), iron (Fe), silicon (Si), tungsten (W), vanadium (V), niobium (Nb), zirconium (Zr), oxygen (O), nitrogen (N), boron (B), fluoride (F), carbidic inclusions and combinations thereof; the additives comprising 50 atomic % or less of the total top layer composition, the balance of top layer composition being carbon and hydrogen. 
     
     
         19 . The bearing of  claim 15  wherein the carbonaceous functional top layer has no additives and consists of only amorphous carbon (C) or hydrocarbon (C and H). 
     
     
         20 . The bearing of  claim 15  wherein the coating includes a gradient layer between the adhesion layer and the top functional layer, the gradient layer transforming from the composition of the adhesion layer to the composition of the final layer.