Patent ID: 7824107

Claim:
A hub unit comprising: a double-row outer ring comprising: a first inner peripheral raceway at a vehicle outer end-side portion; and a second inner peripheral raceway at a vehicle center-side portion; a hub comprising: a wheel-mounting flange provided at the vehicle outer end-side portion, the wheel-mounting flange being provided with a reference surface for mounting a wheel formed on a vehicle outer end-side thereof; a first outer peripheral raceway formed integrally with or separately from the hub at a vehicle center-side of the flange, the first outer peripheral raceway being opposed to the first inner peripheral raceway of the outer ring; a shaft body comprising a distal end fitting portion at the vehicle center-side thereof; and an inner ring element which is fitted on and fixed to the distal end fitting portion, and comprises a second outer peripheral raceway opposed to the second inner peripheral raceway of the outer ring; rolling members interposed between the double-row inner peripheral raceway of the outer ring and the double-row outer peripheral raceway of the hub so as to allow a relative rotation between the outer ring and the hub; and cages holding the rolling members, wherein a plane of the wheel-mounting reference surface of the flange only extends substantially perpendicular to a rotational center of the hub, wherein first and second rust-preventive layers are provided only on an axially-outward side surface of the plane, in this order, wherein the first and second rust-preventive layers are monolithic with the wheel-mounting reference surface of the flange and at least one of a grinding and turning is performed on the second rust preventive layers, wherein the first and second rust-preventive layers are electroplating layers, wherein the hardness of the first rust preventive layer is higher than the hardness of the second rust preventive layer, wherein the thickness of the first layer is between 5 μm and 15 μm, and wherein the first layer is a chrome plating layer or a nickel plating layer.