Buckle apparatus for seat belt system

A buckle device holding a tongue plate mounted to an elongated, strip-shaped webbing belt which is taken-up and accommodated from a proximal end side toward an accommodating direction side which is opposite to a pull-out direction, by an accommodating urging force which increases and decreases in accordance with an amount by which the webbing belt is pulled out toward a pull-out direction side, said buckle device comprising:

• a device main body into which the tongue plate is inserted from a distal end side;
• a latch which is provided at the device main body so as to be movable so as to approach and move away from the tongue plate inserted in the device main body, and which, by moving to approach the tongue plate, mechanically engages with the tongue plate, and limits movement of the tongue plate in a separating direction which is opposite to an insertion direction into the device main body;
• an anchor member which is mounted to a predetermined position of a vehicle, and which supports the device main body such that the device main body is relatively movable in a predetermined range in the insertion direction and the separating direction;
• urging means for urging the device main body in the insertion direction with respect to the anchor member, by urging force which is greater than the accommodating urging force in a state in which the webbing belt is pulled out by a predetermined length;
• a force sensor which is mounted to one of the anchor member and the device main body, and which outputs a load detection signal which is based on pushing force applied from one of the insertion direction and the separating direction;
• and
• a pushing member applying pushing force to the force sensor in accordance with relative movement of the device main body in the separating direction with respect to the anchor member.