Double-row tapered roller bearing unit and method for manufacturing same

A double-row tapered-roller bearing unit, comprising:

• an outer-diameter-side raceway member having a first outer-ring raceway and a second outer-ring raceway formed on the inner-circumferential surface thereof, the first outer-ring raceway and the second outer-ring raceway having partial conical surfaces inclined in directions so that the diameters become larger going in directions away from each other in the axial direction;
• an inner-diameter-side raceway member having a first inner-ring raceway and a second inner-ring raceway formed on the outer-circumferential surface thereof, the first inner-ring raceway and the second inner-ring raceway having partial conical surfaces inclined in directions so that the diameters become larger going in directions away from each other in the axial direction;
• and
• plural tapered rollers rotatably provided respectively between the first outer-ring raceway and the first inner-ring raceway, and between the second outer-ring raceway and the second inner-ring raceway;
• and
• the inner-diameter-side raceway member comprising a first inner ring with the first inner-ring raceway formed on the outer-circumferential surface thereof, a second inner ring with the second inner-ring raceway formed on the outer-circumferential surface thereof, and a shaft member;
• the first inner ring and the second inner ring press-fitted onto the shaft member;
• and the first inner ring and the second inner ring connected and fastened to the shaft member by securing the large-diameter-side end surface of the first inner ring by a crimped section formed by elastically deforming one end section in the axial direction of the shaft member, and
• the relationship of
• the inclination angle θ1 of the first inner-ring raceway in the state before the first inner ring is press-fitted onto the shaft member;
• the inclination angle θ2 of the second inner-ring raceway in the state before the second inner ring is press-fitted onto the shaft member;
• the amount of decrease δθa in the inclination angle of the first inner-ring raceway occurring when the first inner ring is press-fitted onto the shaft member;
• the amount of decrease δθb in the inclination angle of the second inner-ring raceway occurring when the second inner ring is press-fitted onto the shaft member;
• the amount of increase δθk in the inclination angle of the first inner-ring raceway occurring when the crimped section is formed;
• the press-fit interference ΔX1 of the first inner ring with respect to the shaft member;
• and
• the press-fit interference ΔX2 of the second inner ring with respect to the shaft member;
• satisfying the equation
• −θ1+δθa(ΔX1)+θ2−δθb(ΔX2)=δθk
• and
• the inclination angle φ1 of the first inner-ring raceway and the inclination angle Θ2 of the second inner-ring raceway in the state after the crimped section has been formed being both within respective proper ranges.