초록 ▼

A seat belt device is provided where a pretensioner moves a ball train to the distal end side of a ball guide pipe by means of gas discharged from a gas generating device, and the movement rotates the spool for winding the seat belt in a belt winding direction so as to eliminate slack of the seat be

A seat belt device is provided where a pretensioner moves a ball train to the distal end side of a ball guide pipe by means of gas discharged from a gas generating device, and the movement rotates the spool for winding the seat belt in a belt winding direction so as to eliminate slack of the seat belt, while imparting necessary tension to the seat belt by loading rotational resistance on the spool in a belt withdrawing direction with gas pressure exerted on the ball train. The ball stopper stops movement of the ball train before all the balls in the ball train are ejected from the ball guide pipe in a state where the ball train functions to rotate the spool in the belt winding direction.

대표청구항 ▼

What is claimed is: 1. A seat belt retractor, comprising: a spool for winding and holding a seat belt thereon; and a pretensioner including: a ball guide pipe that aligns a plurality of balls to form a ball train; a gas generator for generating gas discharged to move the ball train toward a distal

What is claimed is: 1. A seat belt retractor, comprising: a spool for winding and holding a seat belt thereon; and a pretensioner including: a ball guide pipe that aligns a plurality of balls to form a ball train; a gas generator for generating gas discharged to move the ball train toward a distal end of the ball guide pipe, wherein the spool is rotated in a belt winding direction due to the movement of the ball train to impart tension to the seat belt; and a ball train movement stopper, for stopping the movement of the ball train in the ball guide pipe, wherein the ball train movement stopper is arranged in the ball train at a position where one or more balls are on a distal side of the ball train movement stopper and one or more residual balls remain on a proximal side of the ball train movement stopper. 2. The seat belt retractor according to claim 1, wherein the ball train movement stopper stops the movement of the ball train before all the balls of the ball train are ejected from the ball guide pipe. 3. The seat belt retractor according to claim 2, wherein the pretensioner includes a motion converting device that converts the movement of the ball train into rotational movement, and wherein the ball train movement stopper includes a ball stopper that is arranged in the ball train so as to be movable in the ball guide pipe and that stops the ball train by contacting a motion converting device. 4. The seat belt retractor according to claim 3, wherein the motion converting device includes a ring gear having on its outer periphery external teeth with which the balls engage in a state where the balls are moving, and wherein the ball stopper is formed to have a shape and size so as to block the movement of the ball train by contacting the outer periphery of the ring gear. 5. The seat belt retractor according to claim 1, wherein the ball train includes at least one residual ball that is configured to maintain gas pressure in the ball guide pipe. 6. The seat belt retractor according to claim 5, wherein the ball train movement stopper is arranged in the ball train at a position where one or more residual balls remain on a proximal side of the ball train. 7. The seat belt retractor according to claim 1, wherein the ball train includes a piston ball arranged to be in contact with a proximal end of the ball train and wherein the piston ball is made of an elastic heat-resistant material in order to seal gas discharged by the gas generator. 8. The seat belt retractor according to claim 1, wherein the ball train movement stopper is shaped like a cylinder with round edges, having a longitudinal length of at least one and half times the diameter of one of the plurality of balls and a width at least equal to the diameter of one of the plurality of balls. 9. The seat belt retractor according to claim 1, further comprising a spiral spring, for continuously exerting a rotational urging force on the spool. 10. The seat belt retractor according to claim 1, further comprising a spool pawl for locking the rotation of the spool to prevent withdrawal of the seat belt. 11. The seat belt retractor according to claim 1, wherein a locking activation mechanism causes a spool pawl to lock the rotation of the spool when an acceleration equal to or larger than a predetermined value occurs. 12. The seat belt retractor according to claim 1, further comprising a torsion bar rotatably connected to the spool and connected to a locking base, wherein the torsion bar is configured to absorb energy generated by the torque on the spool due to withdrawing of the seat belt. 13. The seat belt retractor according to claim 1, wherein the plurality of balls are metal spheres. 14. The seat belt retractor according to claim 1, further comprising a coil spring arranged in the ball guide pipe for applying force on the ball train when the gas generator is ignited. 15. A seat belt device, comprising: a seat belt; an anchor for connecting the seat belt to a vehicle body; a tongue attached to the seatbelt, configured to engage a buckle; and a seat belt retractor, attached to the seat belt, further comprising: a spool for winding and holding a seat belt thereon; and a pretensioner including: a ball guide pipe that aligns a plurality of balls to form a ball train; a gas generator for generating gas discharged to move the ball train toward a distal end of the ball guide pipe, wherein the spool is rotated in a belt winding direction due to the movement of the ball train to impart tension to the seat belt; and a ball train movement stopper, for stopping the movement of the ball train in the ball guide pipe, wherein the ball train movement stopper is arranged in the ball train at a position where one or more balls are on a distal side of the ball train movement stopper and one or more residual balls remain on a proximal side of the ball train movement stopper. 16. The seat belt device according to claim 15, wherein the ball train movement stopper stops the movement of the ball train before all the balls of the ball train are ejected from the ball guide pipe. 17. The seat belt device according to claim 16, wherein the pretensioner includes a motion converting device that converts the movement of the ball train into rotational movement, and wherein the ball train movement stopper includes a ball stopper that is arranged in the ball train so as to be movable in the ball guide pipe and that stops the ball train by contacting a motion converting device. 18. The seat belt device according to claim 17, wherein the motion converting device includes a ring gear having on its outer periphery external teeth with which the balls engage in a state where the balls are moving, and wherein the ball stopper is formed to have a shape and size so as to block the movement of the ball train by contacting the outer periphery of the ring gear. 19. The seat belt device according to claim 15, wherein the ball train includes a plurality of residual balls that are configured to maintain gas pressure in the ball guide pipe. 20. The seat belt device according to claim 19, wherein the ball train movement stopper is arranged in the ball train at a position where one or more residual balls remain on a proximal side of the ball train. 21. A seat belt retractor comprising: a spool for winding and holding a seat belt thereon; and a pretensioner including: a ball guide pipe that aligns a plurality of balls to form a ball train; a gas generator for generating gas discharged to move the ball train towards a distal end of the ball guide pipe, wherein the spool is rotated in a belt winding direction due to the movement of the ball train, whereby tension is imparted to the seat belt, a piston component being arranged in the ball guide pipe so as to be in contact with a proximal end of the ball train and to transmit pressure of the gas discharged from the gas generator to the ball train; a ring gear having on its outer periphery external teeth with which the balls engage in a state where the balls are moving; and a ball stopper that is arranged in the ball train so as to be movable in the ball guide pipe and that stops the movement of the ball train in the ball guide pipe by contacting the outer periphery of the ring gear, wherein at least one residual ball is arranged in the ball guide pipe between the ball stopper and the piston component. 22. The seat belt retractor according to claim 21, wherein the piston component functions as a seal to prevent the discharged gas from leaking beyond the piston component. 23. The seat belt retractor according to claim 22, wherein the ball stopper of the pretensioner stops the movement of the ball train before all the balls of the ball train are ejected from the ball guide pipe in a state where the ball train functions to drive the spool to rotate in the belt winding direction. 24. The seat belt retractor according to claim 23, wherein the at least one residual ball of the pretensioner is arranged to remain in the ball guide pipe between the ball stopper and the piston component in a state where the ball stopper stops the movement of the ball train. 25. The seat belt retractor according to claim 21, wherein the ball stopper is formed into a ball shape or a cylindrical shape, having a longitudinal length of approximately one and a half times to twice the diameter of one of the balls and a width approximately the same as the diameter of the ball. 26. A seat belt device comprising a seat belt retractor according to claim 21. 27. A vehicle comprising a seat belt device according to claim 26.