Bearing device for vehicle and method of manufacturing the same

Abstract

A bearing device for a wheel includes an inner ring member including an inner shaft and an inner ring constituent member; an outer ring member; a rolling element; and a wheel-mounting flange formed on a peripheral surface of the inner shaft at a position close to an outer end portion in a vehicle-width direction; a hobbed portion formed on the peripheral surface at a position close to an inner end portion in the vehicle-width direction; and a coupler ring fitted to a periphery of the hobbed portion. A heat-treated portion of the peripheral surface extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction, to a position which is offset from an outer edge of the hobbed portion in the vehicle-width direction toward an outer side in the vehicle-width direction by a predetermined distance, and at which heat treatment does not influence the hobbed portion.

1 . A bearing device for a wheel, comprising:
 an inner ring member that includes an inner shaft and an inner ring constituent member fitted to a periphery of the inner shaft;   an outer ring member that is disposed around a periphery of the inner ring member concentrically with the inner ring member;   a rolling element that is rollably provided between the inner ring member and the outer ring member;   a wheel-mounting flange that protrudes outward, and that is formed on a peripheral surface of the inner shaft at a position close to an outer end portion of the inner shaft in a vehicle-width direction;   a hobbed portion that is a spline portion, and that is formed on the peripheral surface of the inner shaft at a position close to an inner end portion of the inner shaft in the vehicle-width direction; and   a coupler ring which includes an inner peripheral spline portion that engages with the hobbed portion, and which is fitted to a periphery of the hobbed portion,   wherein   a heat-treated portion of the peripheral surface of the inner shaft extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction, to a position which is offset from an outer edge of the hobbed portion in the vehicle-width direction toward an outer side in the vehicle-width direction by a predetermined distance, and at which heat treatment does not influence the hobbed portion.   
   
   
       2 . The bearing device according to  claim 1 , wherein the predetermined distance is 3 to 10 mm. 
   
   
       3 . The bearing device according to  claim 1 , wherein the position is at an inner end of a range where the heat treatment does not influence the hobbed portion, in the vehicle-width direction. 
   
   
       4 . A bearing device for a wheel, comprising:
 an inner ring member that includes an inner shaft and an inner ring constituent member fitted to a periphery of the inner shaft;   an outer ring member that is disposed around a periphery of the inner ring member concentrically with the inner ring member;   a rolling element that is rollably provided between the inner ring member and the outer ring member; and   a wheel-mounting flange that protrudes outward, and that is formed on a peripheral surface of the inner shaft at a position close to an outer end portion of the inner shaft in a vehicle-width direction,   wherein:   a heat-treated portion of the peripheral surface of the inner shaft extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction toward an inner end portion of the inner shaft in the vehicle-width direction, and the heat-treated portion has a predetermined length in an axial direction; and   an outside diameter of the inner shaft at the heat-treated portion is smaller than the outside diameter of the inner shaft at a non-heat-treated portion.   
   
   
       5 . The bearing device according to  claim 4 , wherein a stress that exceeds a predetermined value is concentrated on the heat-treated portion with the predetermined length, when the bearing device is used. 
   
   
       6 . The bearing device according to  claim 5 , wherein:
 the material of the inner shaft is carbon steel for machine structural use; and   the predetermined value is 240 MPa.   
   
   
       7 . The bearing device according to  claim 4 , wherein a difference between the outside diameter of the inner shaft at the non-heat-treated portion and the outside diameter of the inner shaft at the heat-treated portion is in a range of 0.2 to 0.4 mm. 
   
   
       8 . A bearing device for a wheel, comprising:
 an inner ring member that includes an inner shaft and an inner ring constituent member fitted to a periphery of the inner shaft;   an outer ring member that is disposed around a periphery of the inner ring member concentrically with the inner ring member;   a rolling element that is rollably provided between the inner ring member and the outer ring member; and   a wheel-mounting flange that protrudes outward, and that is formed on a peripheral surface of the inner shaft at a position close to an outer end portion of the inner shaft in a vehicle-width direction,   wherein:   a heat-treated portion of the peripheral surface of the inner shaft extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction toward an inner end portion of the inner shaft in the vehicle-width direction, and the heat-treated portion has a first predetermined length in an axial direction; and   an outside diameter of the inner shaft at the heat-treated portion and the outside diameter of the inner shaft at a boundary portion of a non-heat-treated portion, which is adjacent to the heat-treated portion, are smaller than the outside diameter of the inner shaft at the non-heat-treated portion excluding the boundary portion, and the boundary portion has a second predetermined length in the axial direction.   
   
   
       9 . The bearing device according to  claim 8 , wherein a stress that exceeds a predetermined value is concentrated on the heat-treated portion with the first predetermined length, when the bearing device is used. 
   
   
       10 . The bearing device according to  claim 9 , wherein:
 the material of the inner shaft is carbon steel for machine structural use; and   the predetermined value is 240 MPa.   
   
   
       11 . The bearing device according  8 , wherein a difference between the outside diameter of the inner shaft at the non-heat-treated portion excluding the boundary portion and the outside diameter of the inner shaft at the heat-treated portion is in a range of 0.2 to 0.4 mm. 
   
   
       12 . A method of manufacturing a bearing device for a wheel, wherein the bearing device includes an inner ring member that includes an inner shaft and an inner ring constituent member fitted to a periphery of the inner shaft; an outer ring member that is disposed around a periphery of the inner ring member concentrically with the inner ring member; a rolling element that is rollably provided between the inner ring member and the outer ring member; and a wheel-mounting flange that protrudes outward, and that is formed on a peripheral surface of the inner shaft at a position close to an outer end portion of the inner shaft in a vehicle-width direction, the method comprising:
 forming the inner shaft so that an outside diameter of the inner shaft at a first portion is smaller than the outside diameter of the inner shaft at a second portion, wherein the peripheral surface of the inner shaft at the first portion is to be heat-treated, and the peripheral surface of the inner shaft at the second portion is not to be heat-treated; and the first portion extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction toward an inner end portion of the inner shaft in the vehicle-width direction, and the first portion has a predetermined length in an axial direction; and   heat-treating the peripheral surface of the inner shaft at the first portion; and   finishing a peripheral surface of the inner shaft by lathe turning.   
   
   
       13 . The method according to  claim 12 , wherein a stress that exceeds a predetermined value is concentrated on the first portion with the predetermined length, when the bearing device is used. 
   
   
       14 . The method according to  claim 13 , wherein:
 the material of the inner shaft is carbon steel for machine structural use; and   the predetermined value is 240 MPa.   
   
   
       15 . The method according to  claim 12 , wherein a difference between the outside diameter of the inner shaft at the first portion and the outside diameter of the inner shaft at the second portion is in a range of 0.2 to 0.4 mm. 
   
   
       16 . A method of manufacturing a bearing device for a wheel, wherein the bearing device includes an inner ring member that includes an inner shaft and an inner ring constituent member fitted to a periphery of the inner shaft; an outer ring member that is disposed around a periphery of the inner ring member concentrically with the inner ring member; a rolling element that is rollably provided between the inner ring member and the outer ring member; and a wheel-mounting flange that protrudes outward, and that is formed on a peripheral surface of the inner shaft at a position close to an outer end portion of the inner shaft in a vehicle-width direction, the method comprising:
 forming the inner shaft so that an outside diameter of the inner shaft at a first portion and the outside diameter of the inner shaft at a boundary portion of a second portion, which is adjacent to the first portion, are smaller than the outside diameter of the inner shaft at the second portion excluding the boundary portion, wherein the peripheral surface of the inner shaft at the first portion is to be heat-treated, and the peripheral surface of the inner shaft at the second portion is not to be heat-treated; the first portion extends from an inner portion of a base of the wheel-mounting flange in the vehicle-width direction toward an inner end portion of the inner shaft in the vehicle-width direction, and the first portion has a first predetermined length in an axial direction; and the boundary portion has a second predetermined length in the axial direction; and   heat-treating the peripheral surface of the inner shaft at the first portion; and   finishing a peripheral surface of the inner shaft by lathe turning.   
   
   
       17 . The method according to  claim 16 , wherein a stress that exceeds a predetermined value is concentrated on the first portion with the first predetermined length, when the bearing device is used. 
   
   
       18 . The bearing device according to  claim 17 , wherein:
 the material of the inner shaft is carbon steel for machine structural use; and   the predetermined value is 240 MPa.   
   
   
       19 . The bearing device according  16 , wherein a difference between the outside diameter of the inner shaft at the first portion and the outside diameter of the inner shaft at the second portion excluding the boundary portion is in a range of 0.2 to 0.4 mm.