Wheel bearing unit

Abstract

Attachment holes 15 are formed in a plurality of locations in the circumferential direction of the attachment flange 13. The amount “h” of projection, from an attachment surface 14 in the axial direction, of the opening edge peripheral portion of the respective attachment holes 15 is limited to no larger than 10 m under the condition that studs 9 are press-fitted and fixed into the respective attachment holes 15. By this configuration, it is possible to inhibit the runout of the rotor 2 fixed to the attachment surface 14 of the attachment flange 13 and thereby inhibit the judder generated during braking operation.

1 . A wheel bearing unit comprising: a stationary member which is provided with a stationary raceway and does not rotate even in use; a rotary member which is provided with a rotary raceway and rotates in use; an attachment flange provided on the outer peripheral surface of the rotary member; a plurality of attachment holes formed through the attachment flange in the axial direction; a plurality of studs fixed to the attachment flange by press-fit inserting the base end portions thereof into the respective attachment holes; and a plurality of rolling members provided between the stationary raceway and the rotary raceway, 
 wherein in use, a rotatable member for braking is overlappingly connected and fixed to an attachment surface provided in one side surface of the attachment flange by the respective studs and nuts into which the respective studs are threaded,    wherein the amount of projection, from the attachment surface in the axial direction, of the opening edge peripheral portion of the respective attachment holes which is a portion of the attachment surface is limited up to 10 μm under the condition that the respective studs are press-fitted and fixed into the respective attachment holes.    
   
   
       2 . A wheel bearing unit comprising: a stationary member which is provided with a plurality of stationary raceways and does not rotate even in use; a rotary member which is provided with a plurality of rotary raceways and rotates in use; an attachment flange provided on the outer peripheral surface of the rotary member; a plurality of attachment holes formed through the attachment flange in the axial direction; a plurality of studs fixed to the attachment flange by press-fit-inserting the base end portions thereof into the respective attachment holes; and a plurality of rolling members provided between the respective stationary raceways and the respective rotary raceways, 
 wherein one member of the stationary member and the rotary member inwardly located in the radial direction is provided with a first inner raceway which is the stationary raceway or the rotary raceway directly formed in an axially intermediate portion of the outer peripheral surface, a small diameter stepped portion formed at one end portion in the axial direction of the outer peripheral surface, and an inner race securely fitted onto this small diameter stepped portion, and this inner race is formed with a second inner raceway which is the stationary raceway or the rotary raceway formed in the outer peripheral surface thereof and held at one end surface thereof by a crimped section which is formed by outwardly plastically deforming the one member in the radial direction,    and wherein in use, a rotatable member for braking is overlappingly connected and fixed to an attachment surface provided in one side surface of the attachment flange by the respective studs and nuts into which the respective studs are threaded,    wherein the amount of projection, from the attachment surface in the axial direction, of the opening edge peripheral portion of the respective attachment holes which is a portion of the attachment surface is limited up to 10 μm under the condition that the respective studs are press-fitted and fixed into the respective attachment holes.    
   
   
       3 . The wheel bearing unit as claimed in  claim 1  wherein the opening edge peripheral portion of the respective attachment holes is a portion from the opening edge of the respective attachment holes to a thickness of 2.5 mm outwardly in the radial direction.  
   
   
       4 . The wheel bearing unit as claimed in  claim 2  wherein the opening edge peripheral portion of the respective attachment holes is a portion from the opening edge of the respective attachment holes to a thickness of 2.5 mm outwardly in the radial direction.