Bearing unit for wheel

Abstract

The wheel rim of a vehicle wheel is fitted onto a cylindrical positioning portion 19 a, and in this condition, fixed to the hub 8 a using bolts which are threaded into the screw holes 11 a in the rotating flange 10 a, and tightened. As the hub 8 a rotates, the runout in the radial direction of the outer peripheral surface 20 a of the cylindrical positioning portion 19 a is controlled up to 15 μm, to suppress the runout of the vehicle wheel. With this construction, running performance such as riding comfort and diving stability is improved.

1 . A manufacturing method of a bearing unit for a vehicle wheel which comprises a non-rotating outer race, and a rotating hub having an outer end formed with a cylindrical positioning portion which has an outer peripheral surface, comprising: 
 assembling the bearing unit for a vehicle wheel, and then finishing the outer peripheral surface of the cylindrical positioning portion, such that the runout in the radial direction at least in the part of the outer peripheral surface of the cylindrical positioning portion onto which a wheel rim of the vehicle wheel is fitted, is controlled.    
   
   
       2 . A manufacturing method of a bearing unit for rotatably supporting a vehicle wheel on a suspension, which comprises an outer race not rotatable during use, a hub rotating on an inner diameter side of the outer race, and a plurality of rolling elements; the outer race having an inner peripheral surface surface with a double row of outer-race tracks and supported by the suspension; the hub comprising a hub body and an inner race; the hub body provided with a rotating flange formed around an outer peripheral surface of an outer end thereof, such that an outer surface of the rotating flange functions as an installation surface for supporting the vehicle wheel and that the rotating flange has screw holes for fastening the vehicle wheel, a first inner-race track formed directly around the outer peripheral surface in a middle section of the hub body to face the first outer-race track on an outer side of the outer-race tracks, and a cylindrical positioning portion formed on an outer end surface of the hub body, and around which an inner peripheral edge of the vehicle wheel is fitted; the inner race provided with a second inner-race track formed on an outer peripheral surface thereof to face a second outer-race track on an inner side of the outer-race tracks, and being fitted around an inner end section of the hub body; and the rolling elements rotatably located between the respective outer-race tracks and the respective inner-race tracks, comprising: 
 assembling the bearing unit for a vehicle wheel, and then finishing the outer peripheral surface of the cylindrical positioning portion, such that the runout in the radial direction at least in the part of the outer peripheral surface of the cylindrical positioning portion onto which a wheel rim of the vehicle wheel is fitted, is controlled.    
   
   
       3 . The manufacturing method described in  claim 1 , wherein the finishing process is selected from either of turning, grinding and micro-finishing.  
   
   
       4 . The manufacturing method described in  claim 2 , wherein the finishing process is selected from either of turning, grinding and micro-finishing.