Preload inspection method for bearing device for vehicle wheel

A preload inspection method for a bearing device for a vehicle wheel including:

• an outer member having a plurality of rows of outer raceway surfaces on an inner periphery;
• an inner member including a hub ring that has a small-diameter step portion extending in an axial direction on an outer periphery and an inner ring that is press-fitted into the small-diameter step portion of the hub ring, the inner member having a plurality of rows of inner raceway surfaces facing the plurality of rows of outer raceway surfaces;
• and
• a plurality of rows of rolling bodies rollably accommodated between both raceway surfaces of the outer member and the inner member, the preload inspection method comprising:
• a press-fitting step of press-fitting the inner ring into the small-diameter step portion of the hub ring to a position where the inner ring abuts on the hub ring in the axial direction;
• a first inner ring height measurement step of measuring a first inner ring height from an outer-side end portion of the hub ring to an inner-side end portion of the inner ring after the press-fitting step;
• a first bearing preload value calculation step of measuring an axial negative gap between the both raceway surfaces and the rolling body after the press-fitting step and calculating a bearing preload value of the bearing device for a vehicle wheel based on the axial negative gap;
• a post-press-fitting rotational torque measurement step of measuring post-press-fitting rotational torque of the bearing device for a vehicle wheel when the inner member and the outer member are relatively rotated after the press-fitting step;
• a crimping step of crimping an inner-side end portion of the small-diameter step portion to the inner ring after the first inner ring height measurement step and the post-press-fitting rotational torque measurement step;
• a post-crimping temperature measurement step of measuring temperature of a crimped portion between the small-diameter step portion and the inner ring after the crimping step;
• a second inner ring height measurement step of measuring a second inner ring height from an outer-side end portion of the hub ring to an inner-side end portion of the inner ring after the crimping step;
• an inner ring pressing amount estimation step of calculating a pressing amount of the inner ring from a difference between the first inner ring height and the second inner ring height, correcting a pressing amount of the inner ring based on temperature of the crimped portion, and estimating a corrected pressing amount of the inner ring with respect to the hub ring;
• a final gap calculation step of calculating a gap decrease amount between the both raceway surfaces and the rolling body based on the estimated corrected pressing amount of the inner ring, and calculating a final gap between the inner ring and the hub ring based on the gap decrease amount and the axial negative gap;
• a second bearing preload value calculation step of calculating a second bearing preload value of the bearing device for a vehicle wheel based on the calculated final gap;
• a post-crimping rotational torque measurement step of measuring post-crimping rotational torque of the bearing device for a vehicle wheel when the inner member and the outer member are relatively rotated after the crimping step;
• a post-crimping rotational torque correction step of estimating a torque increase amount caused by a temperature change in the post-crimping rotational torque based on temperature of the crimped portion after the crimping step and correcting the post-crimping rotational torque by subtracting the torque increase amount from the post-crimping rotational torque;
• a preload change amount estimation step of calculating differential torque between the post-press-fitting rotational torque and the post-crimping rotational torque after correction and estimating a preload change amount caused by the crimping processing based on the differential torque;
• a third bearing preload value calculation step of calculating a third bearing preload value by adding the preload change amount to the first bearing preload value;
• and
• a determination step of determining appropriateness or inappropriateness of a preload applied to the bearing device for a vehicle wheel based on whether or not each of the second bearing preload value and the third bearing preload value is within a predetermined threshold and whether or not a relative difference between the second bearing preload value and the third bearing preload value is within a predetermined threshold.