Seat belt retractor and seat belt apparatus having the same

Abstract

A seat belt retractor for a seat belt includes a spool for winding the seatbelt, a first seat belt load limiting mechanism for limiting load applied on the seat belt in an emergency, a second seat belt load limiting mechanism for limiting the load applied to the seat belt when a predetermined condition based on an emergency situation is satisfied in the emergency, a driving member for actuating the second seat belt load limiting mechanism, and a controller for controlling the driving member. When the predetermined condition is satisfied, the controller sets the second seat belt load limiting mechanism in an operative state by not actuating the driving member. When the predetermined condition is not satisfied, the controller sets the second seat belt load limiting mechanism in an inoperative state by actuating the driving member.

What is claimed is: 
     
       1. A seat belt retractor for a seat belt, comprising:
 a spool for winding the seatbelt, having a groove thereon; 
 a first seat belt load limiting mechanism for limiting load applied on the seat belt in an emergency; 
 a second seat belt load limiting mechanism for limiting the load applied to said seat belt when a predetermined condition according to an emergency situation in the emergency is satisfied, the second seat belt load limiting mechanism having an energy absorbing member for absorbing energy applied to the seat belt, and a supporting member supporting the energy absorbing member and being disposed coaxially with said spool and rotatable relative to said spool and having another groove thereon; 
 a driving member for actuating said second seat belt load limiting mechanism; 
 a controller for controlling said driving member, electrically connected with the driving member; 
 a locking mechanism having a locking member rotating together with said spool by transmission of rotation of said spool via the first seat belt load limiting mechanism during a non emergency situation, and being prevented from rotating in a seatbelt withdrawing direction in the emergency, wherein the energy absorbing member is disposed between said locking member and said supporting member and is deformed by the rotation of said spool in the seat belt withdrawing direction to absorb the energy applied to the seat belt when the locking member is actuated in the emergency to prevent rotation of the locking member in the seatbelt withdrawing direction; 
 a stopper slidably fitted in the groove of the spool and the another groove of the supporting member; and 
 a stopper operating member operating the stopper, 
 wherein when said predetermined condition is satisfied, the controller does not actuate the driving member so that said second seat belt load limiting mechanism is actuated, 
 wherein when said predetermined condition is not satisfied, the controller actuates the driving member so that said second seat belt load limiting mechanism by actuating said driving member is not actuated, and 
 wherein when said locking member is prevented from rotating in the seat belt withdrawing direction so that said spool rotates in the seat belt withdrawing direction relative to said locking member, the load applied on said seat belt is limited by at least said first seat belt load limiting mechanism. 
 
     
     
       2. A seat belt retractor according to  claim 1  wherein said energy absorbing member comprises a long energy absorbing plate. 
     
     
       3. A seat belt retractor according to  claim 1 , wherein said first seat belt load limiting mechanism comprises a torsion bar disposed between said spool and said locking member. 
     
     
       4. A seat belt apparatus, comprising:
 the seat belt for restraining an occupant; 
 the seat belt retractor according to  claim 1  for winding the seat belt, said seat belt retractor preventing the seat belt from being withdrawn so as to restrain the occupant in the emergency; 
 a tongue slidably supported on the seat belt withdrawn from the seat belt retractor; and 
 a buckle detachably latched with the tongue. 
 
     
     
       5. A seat belt apparatus according to  claim 4 , further comprising a pretensioner for directly rotating said spool in a seat belt winding direction in the emergency. 
     
     
       6. A seat belt retractor according to  claim 1 , wherein the stopper operating member moves in an axial direction of the spool and presses the stopper such that the stopper moves out of engagement with the groove of the supporting member. 
     
     
       7. A seat belt retractor according to  claim 6 , further comprising an operation controlling member having an annular portion and an operating lever extending radially outwardly from the annular portion. 
     
     
       8. A seat belt retractor according to  claim 7 , wherein
 the driving member has a driving piston and a guide hole therein, 
 the operating lever has a tip end orthogonally extending from an end of the operating lever, and 
 the tip end engages in the guide hole and moves from one end of the guide hole to another end of the guide hole to make the operation controlling member operable or inoperable. 
 
     
     
       9. A seat belt retractor according to  claim 8 , wherein the spool and the supporting member rotate relative to each other when the operation controlling member is operable. 
     
     
       10. A seat belt retractor according to  claim 9 , further comprising a pretensioner,
 wherein the pretensioner directly rotates said spool in a seat belt winding direction when the operation controlling member is operable. 
 
     
     
       11. A seat belt retractor according to  claim 1 , wherein while the second seat belt load limiting mechanisms is being actuated when said controller determines that an entire operation of said second seat belt loading limiting mechanism is not required, said controller stops an operation of said second seat belt load limiting mechanism.