Seat belt retractor

Abstract

A seat belt retractor including a spool for winding up the seat belt, and a locking mechanism that prevents rotation of the spool. A belt withdrawal sensor actuates when the seat belt is withdrawn at a speed higher than a normal speed. The locking mechanism is actuated based on the actuation of the belt withdrawal sensor. A lock gear rotates with the spool when the locking mechanism is not in operation and rotates relative to the spool when the lock actuation mechanism is in operation. The lock gear actuates the locking mechanism by relative rotation between the lock gear and the spool. The belt withdrawal sensor is disposed on the lock gear allowing the belt withdrawal sensor to oscillate between an inoperative position and an operative position. An oscillation preventive member prevents the oscillation of the belt withdrawal sensor.

1 . A seat belt retractor for winding up a seat belt comprising:
 a spool for winding up the seat belt;   a locking mechanism that allows the rotation of the spool when the locking mechanism is not in operation and prevents rotation of the spool in a belt withdrawing direction when the locking mechanism is in operation;   a belt withdrawal sensor that is actuated when the seat belt is withdrawn at a speed higher than a normal speed at a start of the withdrawal of the seat belt, and;   a lock actuation mechanism that actuates the locking mechanism based on the actuation of the belt withdrawal sensor, wherein the lock actuation mechanism comprises at least a lock gear that rotates together with the spool when the lock actuation mechanism is not in operation and rotates relative to the spool when the lock actuation mechanism is in operation, the lock gear actuating the locking mechanism by the relative rotation between the lock gear and the spool when the lock actuation mechanism is in operation, and   wherein the belt withdrawal sensor is disposed on the lock gear allowing the belt withdrawal sensor to oscillate between an inoperative position where the belt withdrawal sensor allows the rotation of the lock gear both in the belt winding direction and the belt withdrawing direction and an operative position where the belt withdrawal sensor prevents the rotation of the lock gear at least in the belt withdrawing direction,   the seatbelt retractor further comprising:
 an oscillation preventive member for preventing the oscillation of the belt withdrawal sensor and 
 an oscillation preventive member control mechanism for controlling the movement of the oscillation preventive member, 
 wherein the oscillation preventive member is movable in a radial direction through a rotational center of the spool between an oscillation preventing position where the oscillation preventive member holds the belt withdrawal sensor at the inoperative position to prevent the belt withdrawal sensor from oscillating toward the operative position at least when the seat belt is fully or nearly fully wound, and an oscillation allowing position where the oscillation preventive member allows the oscillation of the belt withdrawal sensor when a certain amount of the seat belt is withdrawn from the fully wound state, and 
 wherein the oscillation preventive member control mechanism comprises a movement control member that rotates at a speed lower than the speed of the spool to control the movement of the oscillation preventive member when the spool rotates. 
   
   
   
       2 . A seat belt retractor as claimed in  claim 1 , further comprising:
 an emergency locking mechanism that detects a vehicle deceleration larger than a normal deceleration and actuates to prevent the spool from rotating in the belt withdrawing direction;   an automatic locking mechanism that is actuated when the seat belt is fully withdrawn and prevents the withdrawal of the seat belt during winding after the seat belt is fully withdrawn until a certain amount of the seat belt is wound; and   a lock switching mechanism for switching between an emergency locking function mode in which an emergency locking function is executed by the emergency locking mechanism and an automatic locking function mode in which an automatic locking function is executed by the automatic locking mechanism,   the lock switching mechanism comprising:
 a switching lever that is selectively set at either of an emergency locking position where the emergency locking function mode is set or an automatic locking position where the automatic locking function mode is set, and 
 an eccentric gear that rotates when the spool rotates, the eccentric gear rotating at a speed lower than the rotational speed of the spool and comprising a switching lever control cam member for switching the setting position of the switching lever, 
 wherein the movement control member comprises the eccentric gear and the oscillation preventive member is a member of which movement is controlled by the rotation of the eccentric gear to prevent the actuation of the belt withdrawal sensor when the seat belt is fully or nearly fully wound. 
   
   
   
       3 . A seat belt retractor as claimed in  claim 2 , wherein the belt withdrawal sensor comprises a ring member and the oscillation preventive member comprises a plurality of stoppers that press an inner periphery of the ring member to prevent actuation of the belt withdrawal sensor when the seat belt is fully or nearly fully wound. 
   
   
       4 . A seat belt retractor as claimed in  claim 3 , wherein the stoppers comprise a stopper biasing member for biasing the stopper in a direction pressing against the ring member. 
   
   
       5 . A seat belt apparatus comprising:
 a seat belt for restraining an occupant;   a seat belt retractor for winding up the seat belt while allowing withdrawal of the seat belt, the seat belt retractor being actuated in the event of an emergency to prevent the withdrawal of the seat belt; wherein the retractor comprises
 a spool for winding up the seat belt; 
 a locking mechanism that allows the rotation of the spool when the locking mechanism is not in operation and prevents rotation of the spool in a belt withdrawing direction when the locking mechanism is in operation; 
 a belt withdrawal sensor that is actuated when the seat belt is withdrawn at a speed higher than a normal speed at a start of the withdrawal of the seat belt, and; 
 a lock actuation mechanism that actuates the locking mechanism based on the actuation of the belt withdrawal sensor, wherein the lock actuation mechanism comprises at least a lock gear that rotates together with the spool when the lock actuation mechanism is not in operation and rotates relative to the spool when the lock actuation mechanism is in operation, the lock gear actuating the locking mechanism by the relative rotation between the lock gear and the spool when the lock actuation mechanism is in operation, and wherein the belt withdrawal sensor is disposed on the lock gear allowing the belt withdrawal sensor to oscillate between an inoperative position where the belt withdrawal sensor allows the rotation of the lock gear both in the belt winding direction and the belt withdrawing direction and an operative position where the belt withdrawal sensor prevents the rotation of the lock gear at least in the belt withdrawing direction, 
 an oscillation preventive member for preventing the oscillation of the belt withdrawal sensor and an oscillation preventive member control mechanism for controlling the movement of the oscillation preventive member, wherein the oscillation preventive member is movable in a radial direction through a rotational center of the spool between an oscillation preventing position where the oscillation preventive member holds the belt withdrawal sensor at the inoperative position to prevent the belt withdrawal sensor from oscillating toward the operative position at least when the seat belt is fully or nearly fully wound, and an oscillation allowing position where the oscillation preventive member allows the oscillation of the belt withdrawal sensor when a certain amount of the seat belt is withdrawn from the fully wound state, and wherein the oscillation preventive member control mechanism comprises a movement control member that rotates at a speed lower than the speed of the spool to control the movement of the oscillation preventive member when the spool rotates. 
   a tongue slidably supported by the seat belt, and   a buckle fixed to a vehicle floor or a vehicle seat and to which the tongue is detachably latched.