Seat belt retractor

Abstract

A seatbelt retractor of the invention intends to stabilize the stopping position of a seatbelt, and to stabilize the resistance thereof. In order to absorb the energy acting on the seatbelt in case of a vehicle emergency, the seatbelt retractor includes a torsion bar 4 (first energy-absorbing means) being the rotational shaft of a take-up drum, a second energy-absorbing means utilizing the pulling of a wire, and a clutch mechanism which immediately switches a state where the first and second energy-absorbing means absorb the energy acting on the seatbelt in case of a vehicle emergency into a state where only the first energy-absorbing means absorbs the energy.

1 . A seatbelt retractor comprises: 
 a take-up drum on which webbing is wound;    a take-up shaft, one end of which is coupled with one end of the take-up drum in a manner that a relative rotation with the take-up drum is impossible, which is biased in the direction of the webbing taken up;    an emergency lock mechanism which restrains a rotation in the direction of the webbing pulled out;    a clutch mechanism located near the other end of the take-up shaft;    a plate body provided close to a side on the other end of the take-up drum, which is provided on the other end of the take-up shaft through the clutch mechanism; and    an energy-absorbing means located between the side of the take-up drum and the plate body, which provides a resistive load by mutually performing a relative rotation;    wherein the clutch mechanism switches a first state where the plate body is provided on the other end of the take-up shaft in a manner that a relative rotation with the take-up shaft is impossible into a second state where the plate body is provided on the other end of the take-up shaft in a manner that a relative rotation with the take-up shaft is possible, and the clutch mechanism includes a clutch release mechanism which actuates a switching at an arbitrary timing.    
   
   
       2 . A seatbelt retractor comprising: 
 a take-up drum on which webbing is wound;    a torsion bar inserted through the take-up drum, one end of which is coupled with one end of the take-up drum in a manner that a relative rotation with the take-up drum is impossible, which is biased in the direction of the webbing taken up;    an emergency lock mechanism located on the other end of the torsion bar, which restrains a rotation in the direction of the webbing pulled out;    a lock actuating device which actuates the emergency lock mechanism in case of a vehicle emergency;    a clutch mechanism located near the other end of the torsion bar;    a plate body provided close to a side on the other end of the take-up drum, which is provided on the other end of the torsion bar through the clutch mechanism; and    a second energy-absorbing means located between the side of the take-up drum and the plate body, which provides a resistive load by mutually performing a relative rotation;    wherein the clutch mechanism switches a first state where the plate body is provided on the other end of the torsion bar in a manner that a relative rotation with the torsion bar is impossible into a second state where the plate body is provided on the other end of the torsion bar in a manner that a relative rotation with the torsion bar is possible, and the clutch mechanism includes a clutch release mechanism which actuates a switching at an arbitrary timing.    
   
   
       3 . A seatbelt retractor according to  claim 2 , wherein the clutch mechanism includes: 
 a joint plate coupled with the emergency lock mechanism in a manner that a relative rotation with the emergency lock mechanism is impossible;    at least one joint pawl pivoted to be turnable to a side of the plate body on the opposite side to the take-up drum, which comes in contact with the joint plate to turn outwardly;    a release ring retained by a casing fixed on a side plate of a housing on the other end of the torsion bar to be movable in the axial direction while rotating, which is located on a periphery of the joint pawl; and    a clutch release mechanism which actuates the release ring attached to the casing.    
   
   
       4 . A seatbelt retractor according to  claim 3 , wherein the clutch release mechanism includes a gas generator which generates gas in a cylinder attached to the casing at an arbitrary timing, and a piston pressed and driven by a gas pressure in the cylinder, which presses the circumference of the release ring to rotate the release ring.  
   
   
       5 . A seatbelt retractor according to  claim 4 , wherein the release ring is provided with a contact on the circumference thereof, which comes in contact with the piston, and plural tapered parts located with a uniform spacing on the circumference thereof, and the casing which holds the release ring is provided with projections corresponding to the tapered parts of the release ring.  
   
   
       6 . A seatbelt retractor according to  claim 1 , wherein the clutch mechanism is provided with a pawl holder which positions and supports the joint pawls, and the pawl holder is provided with ribs integrally formed thereon, which biases the joint pawls in the axial direction and will not return the joint pawls to the initial positions after operating the joint pawls.  
   
   
       7 . A seatbelt retractor according to  claim 2 , wherein the second energy-absorbing means includes a curved path provided on a side of the take-up drum on the other end of the torsion bar, and a wire, one end of which is fixed to a take-up part of the plate body, a substantially medium part of which is located in the curved groove.