Process for manufacturing a hollow roller, hollow roller obtainable via such a process and roller bearing including such a roller

Abstract

A process for manufacturing a hollow roller of a roller bearing including steps of: machining an outer radial cylindrical surface, with a circular cross section centered on a first axis, and machining an inner radial cylindrical surface with a circular cross section centered on a second axis. These two steps are realized on the same lathe. The hollow roller is provided with the outer radial cylindrical surface, with a diameter of at least 5 mm, and the inner radial cylindrical surface. An offset between the first axis and the second axis, measured in the hollow roller between two axial surfaces of the hollow roller, is less than 2 μm, and an inclination angle between the first axis and the second axis is less than one minute of angle. The roller bearing comprises amongst others, at least one such hollow roller.

1 . A process for manufacturing a hollow roller of a roller bearing, the process including steps of:
 a) machining an outer radial cylindrical surface with a circular cross section centered on a first axis;   b) machining an inner radial cylindrical surface with a circular cross section centered on a second axis,   wherein steps a) and b) are realized on the same lathe.   
     
     
         2 . The process according to  claim 1  further comprising a step of using a first mandrel for holding a part in the lathe during steps a) and b) and wherein the first mandrel remains locked on the part between steps a) and b). 
     
     
         3 . The process according to  claim 2  wherein the first mandrel has a central opening through which a single part goes for manufacturing successive hollow rollers. 
     
     
         4 . The process according to  claim 1  wherein steps a) and b) are each performed by a movement of at least one tool along a longitudinal axis of the lathe. 
     
     
         5 . The process according to  claim 4  wherein:
 the tool used for step a) is a cutting insert, and 
 the tool used for step b) is at least one of a drill and a reamer. 
 
     
     
         6 . The process according to  claim 1 , wherein steps a) and b) are performed one after the other. 
     
     
         7 . The process according to  claim 1  wherein steps a) and b) are performed simultaneously. 
     
     
         8 . The process according to  claim 1  further comprising at least a step following steps a) and b) and consisting in:
 c) separating a preform of the hollow roller form a part. 
 
     
     
         9 . The process according to  claim 8  wherein step c) is performed in the lathe. 
     
     
         10 . The process according to  claim 2 , wherein step c) is performed in the lathe, and wherein a second mandrel, different from the first mandrel, is used for holding the machined preform during step c). 
     
     
         11 . The process according to  claim 8 , the process further including at least one of the following steps, performed after step c), the steps consisting in:
 d) grinding the outer cylindrical surface on a centerless machining equipment,   e) grinding axial surfaces of the roller,   f) grinding connecting or corner radii between axial and radial surfaces of the hollow roller,   g) grinding a draught zone or crown between the outer radial cylindrical surface and a zone including a connecting radius.   
     
     
         12 . A hollow roller of a roller bearing, the hollow roller comprising:
 an outer radial cylindrical surface, having a circular cross section centered on a first axis and a diameter of at least 5 mm; and   an inner radial cylindrical surface with a circular cross section centered on a second axis,   wherein an offset between the first axis and the second axis, measured in the hollow roller between two axial surfaces of the hollow roller, is less than 2 μm,   wherein an inclination angle between the first axis and the second axis is less than one minute of angle.   
     
     
         13 . The hollow roller according to  claim 12 , wherein the hollow roller has a hollowness rate above 75%, preferably about 78%. 
     
     
         14 . The hollow roller according to  claim 12 , wherein the hollow roller has a hollowness rate above 78%. 
     
     
         15 . The hollow roller according to  claim 12 , further comprising at least one draught zone between the outer radial cylindrical surface and a zone including a connecting radius with an axial surface of the roller,
 wherein the draught zone converges towards the axial surface.   
     
     
         16 . A roller bearing comprising:
 an inner ring;   an outer ring; and   at least one row of rollers installed in a rolling chamber between the inner ring and the outer ring,   wherein at least one of the rollers, is a hollow roller comprising:
 an outer radial cylindrical surface, having a circular cross section centered on a first axis and a diameter of at least 5 mm; and 
 an inner radial cylindrical surface with a circular cross section centered on a second axis, 
 wherein an offset between the first axis and the second axis, measured in the hollow roller between two axial surfaces of the hollow roller, is less than 2 μm, 
 wherein an inclination angle between the first axis and the second axis is less than one minute of angle. 
   
     
     
         17 . The roller bearing according to  claim 16 , wherein any one of the roller is a hollow roller comprising:
 an outer radial cylindrical surface, having a circular cross section centered on a first axis and a diameter of at least 5 mm; and   an inner radial cylindrical surface with a circular cross section centered on a second axis,   wherein an offset between the first axis and the second axis, measured in the hollow roller between two axial surfaces of the hollow roller, is less than 2 μm,   wherein an inclination angle between the first axis and the second axis is less than one minute of angle.