Patent ID: 7992669

Claim:
A vehicle seat belt apparatus including an electric pretensioner that includes a belt reel and a motor for rotationally driving the belt reel to take up a belt, said vehicle seat belt apparatus comprising: a take-up position detector for detecting a take-up position of the belt reel; a traveling condition detector for detecting a traveling condition of the vehicle; a traveling condition determination apparatus for determining, on the basis of a detection signal output by said traveling condition detector, whether the traveling condition of the vehicle has exceeded a predetermined threshold amount; and a control apparatus for controlling power supply to the motor, on the basis of a determination signal output by said traveling condition determination apparatus, to thereby control a driving amount of the motor while also controlling the belt reel, in accordance with the detection signal output by said take-up position detector, so that the belt reel is kept at a predetermined take-up position, to thereby hold a vehicle occupant with the belt; wherein said control apparatus is operable to variably select and set a gain level for controlling a rate of power supplied to the motor, depending on sensed operating conditions, in order to adjust the responsiveness of the motor; said sensed operating conditions including a rate of change in the traveling condition and a difference between a current take-up position and a target take-up position; wherein when an amount of variation in the traveling condition exceeds the predetermined threshold amount, the gain level is increased so as to make an actual current take-up position of the belt reel approach the target take-up position thereof; wherein the control apparatus is operable to determine an upper limit of the power supplied to the motor, based on a difference between the target take-up position of the belt reel and the actual current take-up position thereof; and wherein, when an amount of variation in the traveling condition exceeds the predetermined threshold amount, the gain level is increased by an amount corresponding to the sensed difference between the current take-up position and the target take-up position.