Seat belt retractor

Abstract

A seat belt retractor includes a seat belt, a spool, and an emergency locking mechanism for preventing the spool from rotating in a belt withdrawal direction. The emergency locking mechanism allows rotation of the spool not in operation and prevents the rotation of the spool in the belt withdrawal direction when in operation. A lock gear includes ratchet teeth on an outer periphery of the emergency locking mechanism arranged in an annular shape. The lock gear rotates with the spool when the emergency locking mechanism is not in operation and actuates the locking mechanism when the emergency locking mechanism is in operation. A vehicle sensor includes an engaging claw and detects a vehicle deceleration larger than a predetermined deceleration. The engaging claw engages with one of the ratchet teeth to prevent rotation of the lock gear in the belt withdrawal direction.

1 . A seat belt retractor, comprising:
 a spool that is rotatably supported by a frame to wind up a seat belt;   an emergency locking mechanism for detecting a vehicle deceleration larger than a predetermined threshold, preventing the spool from rotating in a belt withdrawal direction, the emergency locking mechanism comprising:
 at least one locking mechanism allowing rotation of the spool when the emergency locking mechanism is not in operation and preventing the rotation of the spool in the belt withdrawal direction when the emergency locking mechanism is in operation; 
 a lock gear comprising ratchet teeth on an outer periphery of the emergency locking mechanism and arranged in an annular shape, the lock gear rotating together with the spool when the emergency locking mechanism is not in operation and actuating the locking mechanism when the emergency locking mechanism is in operation creating a relative rotation between the lock gear and spool; and 
 a vehicle sensor comprising an engaging claw and detecting a vehicle deceleration larger than the predetermined deceleration in the event of an emergency, the vehicle sensor actuated to engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear; and 
   a first end lock preventive mechanism for preventing the engaging claw of the vehicle sensor from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound by the spool, the first end lock preventive mechanism comprising:
 an end lock preventive member disposed on the frame and set at a locking position where the end lock preventive member does not allow the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound and is set at a non-locking position where the end lock preventive member allows the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear other than when the seat belt is fully or nearly fully wound; and 
 a control element that sets the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and sets the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound. 
   
   
   
       2 . The seat belt retractor as claimed in  claim 1 , further comprising an automatic locking mechanism that is actuated when the seat belt is fully withdrawn and prevents the withdrawal of the seat belt by winding the seat belt after the seat belt is fully withdrawn until a certain amount of the seat belt is wound, and a lock switching mechanism for switching an emergency locking function mode in which an emergency locking function by the emergency locking mechanism is exercised and an automatic locking function mode such that an automatic locking function by the automatic locking mechanism is exercised, wherein the control element is disposed on a control member of the lock switching mechanism. 
   
   
       3 . The seat belt retractor as claimed in  claim 2 , wherein the lock switching mechanism comprises 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 and at a speed lower than the rotation speed of the spool and that has switching lever control cam member for switching the setting position of the switching lever, wherein the control member of the lock switching mechanism is composed of the eccentric gear and the end lock preventive member is composed of an end lock preventive lever that is selectively set at either of the locking position or the un-locking position, and wherein the control element is an end lock preventive member control cam for switching the setting position of the end lock preventive lever. 
   
   
       4 . A seat belt retractor as claimed in  claim 3 , further comprising a webbing sensor that is pivotally disposed on the lock gear and that detects a withdrawal acceleration larger than normal withdrawal acceleration for wearing the belt when the seat belt is rapidly withdrawn and is thus actuated to prevent the rotation of the lock gear in the belt withdrawing direction so as to create a relative rotation between the spool and the lock gear, and a second end lock preventive mechanism for preventing the actuation of the webbing sensor when the seat belt is fully or nearly fully wound. 
   
   
       5 . A seat belt retractor as claimed in  claim 4 , wherein the second end lock preventive mechanism has an actuation preventive member that is controlled its actuation by the eccentric gear and prevents the actuation of the webbing sensor when the belt is fully or nearly fully wound. 
   
   
       6 . A seat belt retractor as claimed in  claim 5 , wherein the second end lock preventive mechanism further includes a ring member disposed on the webbing sensor, and wherein said actuation preventive member is a stopper that presses the ring member to prevent the actuation of the webbing sensor when the seat belt is fully or nearly fully wound. 
   
   
       7 . A seat belt retractor as claimed in  claim 6 , wherein the stopper is provided with a stopper biasing means for biasing the stopper in such a direction that the stopper presses the ring member. 
   
   
       8 . A seat belt apparatus comprising:
 a seat belt for restraining an occupant;   a seat belt retractor for winding up the seat belt while allowing the withdrawal of the seat belt, the seat belt retractor actuated in the event of an emergency to prevent the withdrawal of the seat belt; wherein the retractor includes a spool that is rotatably supported by a frame to wind up the seat belt and an emergency locking mechanism for detecting a vehicle deceleration larger than a predetermined threshold, preventing the spool from rotating in a belt withdrawal direction, the emergency locking mechanism comprising:
 at least one locking mechanism allowing rotation of the spool when the emergency locking mechanism is not in operation and preventing the rotation of the spool in the belt withdrawal direction when the emergency locking mechanism is in operation; and 
 a lock gear comprising ratchet teeth on an outer periphery of the emergency locking mechanism and arranged in an annular shape, the lock gear rotating together with the spool when the emergency locking mechanism is not in operation and actuating the locking mechanism when the emergency locking mechanism is in operation creating a relative rotation between the lock gear and spool; and 
 a vehicle sensor including an engaging claw and detecting a vehicle deceleration larger than the predetermined deceleration in the event of an emergency, the vehicle sensor actuated to engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear; and 
   a first end lock preventive mechanism for preventing the engaging claw of the vehicle sensor from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound by the spool, the first end lock preventive mechanism comprising:
 an end lock preventive member disposed on the frame and set at a locking position where the end lock preventive member does not allow the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound and is set at a non-locking position where the end lock preventive member allows the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear other than when the seat belt is fully or nearly fully wound; and 
 a control element that sets the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and sets the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound. 
   a tongue slidably supported by the seat belt; and   a buckle that is fixed to a vehicle floor or a vehicle seat and to which the tongue can be detachably latched.