Wheel bearing apparatus and its pre-pressure managing method

A wheel bearing apparatus comprising:

• an outer member formed with double row outer raceway surfaces on its inner circumference;
• an inner member including a wheel hub and at least one inner ring, the wheel hub is integrally formed, on its one end, with a wheel mounting flange, a cylindrical portion axially extends from the wheel mounting flange, the at least one inner ring is press-fit onto the cylindrical portion of the wheel hub, via a predetermined interference, the inner member outer circumference includes inner raceway surfaces corresponding to the outer raceway surfaces of the outer member;
• double row rolling elements are rollably contained between the inner and outer raceway surfaces of the inner and outer members, via cages;
• a coupler ring, formed with an inner circumferential splined portion and an outer circumferential splined portion, is fit onto the end portion of the cylindrical portion of the wheel hub, the at least one inner ring is axially secured on the wheel hub, via the coupler ring by a caulked portion, the caulked portion is formed by plastically deforming the end of the cylindrical portion radially outward;
• the inner circumferential splined portion of the coupler ring comprises a plurality of spline recesses and a plurality of spline projections alternately formed with each other and adapted to mate with a hub splined portion including a plurality of spline recesses and a plurality of spline projections alternately formed on the inner-side outer circumference of the cylindrical portion of the wheel hub;
• an axial cross-section of the inner-side end of each spline projection of the hub splined portion is formed by a single circular arc with a predetermined radius of curvature “R”;
• the radius of curvature “R” is larger than a dimension “A”, measured from the inner-side end face of the coupler ring to the inner-side edge “B” of each spline projection (R>A), and is also larger than a height “h” of each spline projection (R>h);
• and
• a tapered surface is formed on the inner circumference of at least an inner-side end of the spline projection of the inner circumferential splined portion of the coupler ring, and wherein a starting point “T” of the tapered surface is positioned within a range between the edge “B” of the spline projection of the hub splined portion and the bottom “C” of the spline recess.

A wheel bearing apparatus comprising:

• an outer member formed with double row outer raceway surfaces on its inner circumference;
• an inner member including a wheel hub and at least one inner ring, the wheel hub is integrally formed, on its one end, with a wheel mounting flange, a cylindrical portion axially extends from the wheel mounting flange, the at least one inner ring is press-fit onto the cylindrical portion of the wheel hub, via a predetermined interference, the inner member outer circumference includes inner raceway surfaces corresponding to the outer raceway surfaces of the outer member;
• double row rolling elements are rollably contained between the inner and outer raceway surfaces of the inner and outer members, via cages;
• a coupler ring, formed with an inner circumferential splined portion and an outer circumferential splined portion, is fit onto the end portion of the cylindrical portion of the wheel hub, the at least one inner ring is axially secured on the wheel hub, via the coupler ring by a caulked portion, the caulked portion is formed by plastically deforming the end of the cylindrical portion radially outward and the coupler ring is formed from steel containing a carbon amount same or less than that of medium-high carbon steel, and a hardness of the outer circumferential splined portion is set same as that of the inner circumferential splined portion;
• the inner circumferential splined portion of the coupler ring comprises a plurality of spline recesses and a plurality of spline projections alternately formed with each other and adapted to mate with a hub splined portion including a plurality of spline recesses and a plurality of spline projections alternately formed on the inner-side outer circumference of the cylindrical portion of the wheel hub;
• an axial cross-section of the inner-side end of each spline projection of the hub splined portion is formed by a single circular arc with a predetermined radius of curvature “R”;
• and
• the radius of curvature “R” is larger than a dimension “A”, measured from the inner-side end face of the coupler ring to the inner-side edge “B” of each spline projection (R>A), and is also larger than a height “h” of each spline projection (R>h).

A wheel bearing apparatus comprising:

• an outer member formed with double row outer raceway surfaces on its inner circumference;
• an inner member including a wheel hub and at least one inner ring, the wheel hub is integrally formed, on its one end, with a wheel mounting flange, a cylindrical portion axially extends from the wheel mounting flange, the at least one inner ring is press-fit onto the cylindrical portion of the wheel hub, via a predetermined interference, the inner member outer circumference includes inner raceway surfaces corresponding to the outer raceway surfaces of the outer member;
• double row rolling elements are rollably contained between the inner and outer raceway surfaces of the inner and outer members, via cages;
• a coupler ring, formed with an inner circumferential splined portion and an outer circumferential splined portion, is fit onto the end portion of the cylindrical portion of the wheel hub, the at least one inner ring is axially secured on the wheel hub, via the coupler ring by a caulked portion, the caulked portion is formed by plastically deforming the end of the cylindrical portion radially outward and the coupler ring is formed of steel containing Cr of 0.9˜1.2% by weight and the surface hardness of the coupler ring is set within a range of 392˜600 HV;
• the inner circumferential splined portion of the coupler ring comprises a plurality of spline recesses and a plurality of spline projections alternately formed with each other and adapted to mate with a hub splined portion including a plurality of spline recesses and a plurality of spline projections alternately formed on the inner-side outer circumference of the cylindrical portion of the wheel hub;
• an axial cross-section of the inner-side end of each spline projection of the hub splined portion is formed by a single circular arc with a predetermined radius of curvature “R”;
• and
• the radius of curvature “R” is larger than a dimension “A”, measured from the inner-side end face of the coupler ring to the inner-side edge “B” of each spline projection (R>A), and is also larger than a height “h” of each spline projection (R>h).