Safety belt retractor having a pretensioning device

Abstract

A safety belt retractor, especially for use in motor vehicles, is provided, and has a blocking system and a tensioning device, which acts on a belt shaft, for carrying out a reversible pretensioning of an occupant. A spiral toothing meshes with an external toothing of the belt shaft, and is supported against a fixed counter-bearing such that upon an axial loading of the spiral toothing directed against the counter-bearing due to load acting on the belt shaft in a belt withdrawal direction, rotation of the spiral toothing, for receiving torque applied by the belt shaft, is prevented via a support force. An electric motor is coupled to the belt shaft via the spiral toothing.

1 - 16 . (canceled)  
   
   
       17 . A belt shaft retractor having a blocking system that is controlled in a vehicle sensitive and/or belt strap sensitive manner, and also having a tensioning device, which acts on the belt shaft ( 12 ), for carrying out a reversible pretensioning of a vehicle occupant, comprising: 
 a spiral toothing ( 19 ) that meshes with an external toothing ( 20 ) of the belt shaft ( 12 );    a fixed counter-bearing ( 23 ) wherein said spiral toothing ( 19 ) is supported against said counter-bearing such that upon an occurrence of an axial loading of said spiral toothing ( 19 ) directed against said counter-bearing ( 23 ) due to a load acting upon said belt shaft ( 12 ) in a belt withdrawal direction, a rotation of said spiral toothing, for receiving a torque applied by said belt shaft ( 12 ) is prevented via a support force; and    an electric motor ( 16 ) as a tensioner drive, wherein said electric motor is adapted to be coupled to said belt shaft ( 12 ) via said spiral toothing ( 19 ).    
   
   
       18 . A safety belt retractor according to  claim 17 , wherein said spiral toothing ( 19 ) is coupled to a drive shaft ( 34 ) of said electric motor ( 16 ) via a miter-wheel gearing ( 17 ).  
   
   
       19 . A safety belt retractor according to  claim 18 , wherein said miter-wheel gearing ( 17 ) is embodied as a crown wheel gear mechanism ( 17 ).  
   
   
       20 . A safety belt retractor according to  claim 18 , wherein said spiral toothing ( 19 ) is formed on a carrier shaft ( 18 ), and wherein said carrier shaft ( 18 ) is connected to the miter-wheel gearing ( 17 ).  
   
   
       21 . A safety belt retractor according to  claim 17 , wherein a friction-increasing component ( 25 ,  26 ,  28 ,  30 ) is disposed between said counter-bearing ( 23 ) and a first thread of said spiral toothing ( 19 ).  
   
   
       22 . A safety belt retractor according to  claim 21 , wherein a spacer disk ( 25 ) of a material having a non-linear coefficient of friction is provided.  
   
   
       23 . A safety belt retractor according to  claim 21 , a bearing disk ( 26 ) is provided that deforms axially and elastically as load increases.  
   
   
       24 . A safety belt retractor according to  claim 21 , wherein a surface of said counter-bearing ( 23 ) that faces said spiral toothing ( 19 ) is provided with a conical recess ( 27 ), and wherein disposed on said carrier shaft ( 18 ) is a conical friction body ( 28 ) that has a corresponding shape and is made of an elastic material.  
   
   
       25 . A safety belt retractor according to  claim 21 , wherein a compress spring ( 30 ) is disposed between said counter-bearing ( 23 ) and said spiral toothing ( 19 ), and wherein said carrier shaft ( 18 ) and said counter-bearing ( 23 ) are provided with latching structures ( 31 ) that interlock during an axial displacement of said carrier shaft ( 18 ).  
   
   
       26 . A safety belt retractor according to  claim 17 , wherein said spiral toothing ( 19 ) is formed on a carrier shaft ( 18 ), and wherein an end face of said carrier shaft is supported against a shank ( 33 ) of a drive shaft ( 34 ) of said electric motor ( 16 ).  
   
   
       27 . A safety belt retractor according to  claim 17 , wherein a crown wheel toothing of a crown wheel gear mechanism ( 17 ) that is effective between a drive shaft ( 34 ) of said electric motor ( 16 ) and a carrier shaft ( 18 ) on which is formed said spiral toothing ( 19 ) has a multi-stage configuration such that during an axial loading of said carrier shaft ( 18 ), a transmission of said crown wheel gear mechanism ( 17 ) changes.  
   
   
       28 . A safety belt retractor according to  claim 17 , wherein said electric motor ( 16 ) is designed with a further performance range for applying a holding moment to aids in prevention of rotation of said spiral toothing ( 19 ).  
   
   
       29 . A safety belt retractor according to  claim 28 , wherein said holding moment of said electric motor ( 16 ) is adjustable via a motor control as a function of load acting on said belt shaft ( 12 ) in a belt withdrawal direction.  
   
   
       30 . A safety belt retractor according  claim 20 , wherein said carrier shaft ( 18 ), which carries said spiral toothing ( 19 ), on an end thereof opposite said miter-wheel gearing is held in a first bearing ( 21 ), and wherein in a region between said spiral toothing ( 19 ) and said miter-wheel gearing ( 17 ) said carrier shaft ( 18 ) is mounted in an additional thrust bearing ( 22 ) that is surrounded by a bearing housing ( 23 ).  
   
   
       31 . A safety belt retractor according to  claim 30 , wherein said thrust bearing is embodied as a cup-shaped bearing ( 22 ).  
   
   
       32 . A safety belt retractor according to  claim 30 , wherein said bearing housing ( 23 ) forms said counter-bearing forms said spiral toothing ( 19 ).