Abstract:
A belt-buckle tightener for a seat belt system in a vehicle, having: a rotatable spindle which is connected to a belt buckle via a draw-in cable; and a drive for rotation of the spindle, as a result of which the draw-in cable is rolled up on the spindle and the belt buckle is moved in the tightening direction, and the drive being integrated in the spindle. Integration of the drive in the spindle reduces the structural space required. In addition, the number of individual parts which are required is reduced since, inter alia, a separate driving spindle is not required. Rather, the spindle for winding up the draw-in cable at the same time forms the driving spindle.

Description:
BACKGROUND 
   The invention relates to a belt-buckle tightener for a seat belt system in a vehicle. 
   A belt-buckle tightener is disclosed, for example, in EP-A1-0662408 (incorporated by reference herein). The function of a belt-buckle tightener of this type is based on the fact that a piston which is connected to a belt buckle via a draw-in cable is displaced by means of a pyrotechnic charge in order thereby to tighten the belt in the event of an accident. 
   A particular disadvantage of a belt-buckle tightener of this type is the structural space which is required for the pyrotechnically driven pistons. 
   DE-A1-4319955 (incorporated by reference herein) discloses a belt-buckle tightener in which a rotary actuator is used instead of a pyrotechnically driven piston. The rotary actuator is actuated by a pyrotechnic driving unit. In addition, an arresting device in the form of a rack is provided and is intended to prevent the belt buckle from shifting counter to the tightening direction. At any rate, the rotary actuator of this belt-buckle tightener requires less structural space than a pyrotechnically driven piston. Nevertheless, even here the rotary actuator, the pyrotechnic driving unit and the arresting device require a large amount of structural space. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a space-saving belt tightener. 
   According to the invention, a belt-buckle tightener for a seat belt system in a vehicle is provided, having: a rotatable spindle which is connected to a belt buckle via a draw-in cable; and a drive for rotation of the spindle, as a result of which the draw-in cable is rolled up on the spindle and the belt buckle is moved in the tightening direction, and the drive being integrated in the spindle. 
   Integration of the drive in the spindle reduces the structural space which is required. In addition, the number of individual parts which are required is reduced since, inter alia, a separate driving spindle is not required. Rather, the spindle for winding up the draw-in cable at the same time forms the driving spindle. 
   A displacement of the belt buckle is achieved by rotary instead of translatory movement. One advantage of this approach is, in particular, that the structural space required for the belt-buckle tightener is virtually independent of the degree of belt-buckle tightening which is to be produced, but in any case is smaller than with conventional piston devices. 
   A further advantage is that, in order to form the belt-buckle tightener, components can be used which are also used in belt retractors. The outlay and the costs of developing and producing the belt-buckle tightener are therefore reduced. 
   In one refinement of the invention, the belt-buckle tightener comprises a coupling sleeve which is connected in a rotationally fixed manner to a frame of the vehicle chassis, the spindle being mounted rotatably on the coupling sleeve, and the drive comprising a gas generator which is fastened to the spindle, and a driving belt, which is fastened at both of its ends to the coupling sleeve and, in the inoperative state of the belt-buckle tightener, is partially wound up on the coupling sleeve and runs around the gas generator, the driving belt thus bounding a space, and gas which is produced by the gas generator flowing into the space, acting upon the driving belt and thereby enlarging the space, as a result of which the driving belt is unwound from the coupling sleeve, produces a driving force and causes the spindle to rotate. 
   This refinement has the advantage that an integrated spindle drive having a small number of additional components can be produced. In particular, this refinement is also distinguished by a good efficiency ratio with regard to the volume of structural space which is required. 
   The driving belt, in the inoperative state of the belt tightener, can additionally run around one or more guide elements. The space bounded by the driving belt can be defined as desired by means of the guide elements, in particular in order to optimally convert the energy produced by the gas generator into rotation of the spindle. 
   In one advantageous refinement, the spindle is coupled to a blocking device which blocks rotation of the spindle counter to the rolling-up direction of the draw-in cable and prevents the draw-in cable from unrolling. The blocking device can be formed by a toothing on the circumference of the spindle and a latch on the vehicle chassis, it being possible for the latch to be brought into engagement with the toothing, and the toothing being designed in such a manner that engagement takes place only when the spindle is rotated counter to the rolling-up direction of the draw-in cable. 
   Integration of the blocking device on the spindle enables the demand for structural space to be additionally reduced. 
   In summary, the belt-buckle tightener is therefore distinguished by its compact manner of construction and the possibility of being able to use standard components. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below. 
       FIG. 1  schematically shows a belt device with a belt-buckle tightener according to a first refinement of the invention; 
       FIG. 2  schematically shows a belt device with a belt-buckle tightener according to an alternative refinement of the invention; 
       FIG. 3  schematically shows an attachment of the draw-in cable on the spindle according to one refinement of the invention; 
       FIG. 4  schematically shows a first view of a belt-buckle tightener according to one refinement of the invention; 
       FIG. 5  schematically shows a second view of the belt-buckle tightener from  FIG. 4 ; 
       FIG. 6  schematically shows the spindle drive of the belt-buckle tightener from  FIGS. 4 and 5 ; and 
       FIG. 7  schematically shows the coupling sleeve of the belt-buckle tightener of  FIGS. 4 to 6 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  schematically shows a belt device with a belt-buckle tightener according to one refinement of the invention. The belt device comprises a belt buckle  1  for securing a belt  2  with respect to the vehicle chassis  30 . The belt-buckle tightener comprises a winding-up device  10  which is secured on the vehicle chassis and has a spindle  11  for the rolling up of a (steel) draw-in cable  12  which is secured at one end on the spindle  11  and at the other end on the vehicle chassis  30  or on a frame of the belt-buckle tightener. In between, the draw-in cable  12  runs around a deflection pulley  13  on the belt buckle  1 . The deflection pulley  13  is contained in the housing of the belt buckle  1 . 
     FIG. 1  shows the belt-buckle tightener in the non-activated state. In an accident, the spindle  11  is caused to rotate, so that the draw-in cable  12  is rolled up and the belt buckle  1  is displaced towards the securing of the draw-in cable  12  on the vehicle chassis  30 . Depending on the design, in particular as a function of the thickness and length of the draw-in cable  12 , a guide is provided along which the belt buckle  1  is displaced. The rotation of the spindle  11  is indicated by the arrow  14  and the displacement of the belt buckle  1  is indicated by the arrow  15 . 
   The rotation of the spindle  11  can be triggered, for example, by means of a pyrotechnic charge. The rotation of a spindle by means of a pyrotechnic charge is known as such and therefore does not need to be described more specifically. However, instead of a pyrotechnic charge, other torque-generating devices may also be used. 
   If, instead of a pyrotechnic charge, an electric torque-generating device is used, the spindle  11  can also be rotated counter to the arrow direction of the arrow  14 , which causes the belt buckle  1  to move counter to the arrow direction  15 . The tightening process of the belt buckle  1  is then reversible. 
   In addition, the spindle  11  is provided with a blocking device which prevents it from rotating back (counter to the direction of the arrow  14 ). Blocking devices of this type are also known as such and therefore are not explained further. 
     FIG. 2  schematically shows a belt device with a belt-buckle tightener according to an alternative refinement of the invention. The belt buckle  1  is connected here to a fastening fitting  3  whose end which faces away from the belt buckle  1  is mounted displaceably by means of a guide pin  4  in a slot  5  of a securing plate  6 . That end of the securing plate  6  which faces away from the belt buckle  1  is fastened to the vehicle chassis. 
   In this case too, the belt-buckle tightener comprises a winding-up device  10  which is secured on the vehicle chassis and has a spindle  11  for the rolling up of a draw-in cable  12  which is fastened at one end to the spindle  11  and at the other end to the fastening fitting  3 . Between the fastening fitting  3  and the spindle  11  the draw-in cable  12  runs around a deflection pulley  13  at that end of the securing plate  6  which is opposite the belt buckle  1 . 
   The function corresponds to that of the belt-buckle tightener from  FIG. 1 : in an accident, the spindle  11  is caused to rotate, so that the draw-in cable  12  is rolled up and the belt buckle  1  is displaced towards the securing of the securing plate  6  on the vehicle chassis. The rotation of the spindle  11  is also indicated here by the arrow  14  and the displacement of the belt buckle  1  is indicated by the arrow  15 . 
     FIG. 3  schematically shows a cable attachment according to one refinement of the invention. According to this, the spindle  11  has a radial hole with two sections of different diameter, so that a shoulder  20  is formed in the transition region of the two sections. 
   At its end provided for fastening to the spindle  11 , the draw-in cable  12  has an end piece  21  with a larger cross-sectional surface than the draw-in cable  12 . The transition region from the end piece  21  to the cable  12  therefore likewise forms a shoulder  22  which sits on the complementary shoulder  20  in the spindle  11  and, if a tensile force is in action (arrow  23 ) on the draw-in cable  12 , prevents the draw-in cable  12  from being detached from the spindle  11 . 
     FIGS. 4 and 5  show a belt-buckle tightener according to one refinement of the invention. The belt-buckle tightener contains a pyrotechnic drive which is integrated in the spindle  11 . For this purpose, the interior of the spindle  11  contains a combustion chamber  40  in which a gas generator  41  is arranged. One refinement of the pyrotechnic drive is described in greater detail further below with reference to  FIG. 6 . 
   The spindle  11  is mounted rotatably on a coupling sleeve  42 . The coupling sleeve  42  in turn is connected fixedly to a U-shaped frame  43  of the vehicle chassis  30 , for example by means of screws  44 . 
   A blocking toothing  45  is provided on the circumference of the spindle  11 . Arranged on the frame  43  is a spring-loaded latch  46  which can be brought into engagement with the blocking toothing  45 . The teeth of the blocking toothing  45  are angled counter to the direction of rotation  47  of the spindle  11  during the tightening process, so that the blocking latch  46  slides away over the teeth when the spindle  11  rotates in the direction of rotation  47  while, in the reverse direction of rotation, the said blocking latch engages in the blocking toothing  45  and blocks the spindle  11 . 
   The attachment of the draw-in cable  12  on the spindle  11  (reference number  48 ) is also illustrated and corresponds in principle to the attachment illustrated in  FIG. 3 . 
     FIG. 6  shows a more precise illustration of the pyrotechnic drive which is integrated in the spindle  11 . As already mentioned, the spindle  11  is mounted rotatably on the coupling sleeve  42 . To drive the spindle  11 , a metal belt  60 , which preferably consists of steel, is fastened (attached) at both ends to the coupling sleeve  42 . The metal belt  60  runs around the gas generator  41 ; in the inoperative state, a remaining part of the metal belt  60  is stored, i.e. wound up, on the coupling sleeve  42 . In addition, part of the metal belt  60  is guided around guide elements  63 , thereby forming a space  64  into which the gas produced by the gas generator  41  flows and acts upon the metal belt  60 . 
   If the gas generator  41  is ignited, the expanding combustion gas acts upon that part of the metal belt  60  which runs around the gas generator  41  and the guide elements  63 , and moves said part radially outwards, as indicated by arrows  61 . In this process, that part of the metal belt  60  which is stored on the coupling sleeve  42  is unwound from the latter. This produces a driving torque which causes the rotatably mounted spindle  11  to rotate. 
   The gas-permeable casing surface of the spindle  11  delimits, by means of its inner side, the maximum, theoretically possible expansion volume of the combustion chamber  40 , as shown by the reference number  62 . As  FIGS. 4 and 5  show, the draw-in cable  12  is fastened to the outer side of the gas-permeable casing surface of the spindle  11 . The ignition of the gas generator  41  and the resulting rotation of the spindle  11  causes the draw-in cable  12  to be wound onto the spindle  11 . Since the draw-in cable  12  is connected to the belt buckle  1 , the latter is tightened in a translatory manner towards the vehicle floor. 
   The locking of the spindle  11  against an oppositely directed rotation after the tightening process takes place by means of the latch  46  which engages in the toothing  45 , as illustrated in  FIGS. 4 and 5 . 
     FIG. 7  shows a more precise illustration of the coupling sleeve  42 . On its circumference, the coupling sleeve has a fastening region  70  for attachment of the metal belt  60 . Along its longitudinal axis, the coupling sleeve  42  comprises three sections: a cylindrical central section  71  runs between the base areas of the spindle  11  and is used for attachment of the metal belt  60 . This central section  71  runs between cylindrical sections  72  which serve for rotatable mounting (reference number  73 ) of the spindle  11  on the coupling sleeve  42 . The outside diameter of the sections  72  corresponds essentially to the diameter of corresponding, circular cutouts  74  in the spindle  11 . The outside diameter of the sections  72  is smaller than that of the central section  71 , as a result of which an axial displacement of the spindle  11  relative to the coupling sleeve  42  is prevented. 
   At the axially outer ends of the coupling sleeve, end sections  75  adjoin the cylindrical sections  72 . The end sections  75  have a square base area for accommodation in corresponding, square cutouts  76  in the frame  43 . As a result, the coupling sleeve  42  is mounted in a rotationally fixed manner in the frame  43 . The base area of the end sections  75  and the corresponding cutouts in the frame  43  may also have any other desired angular shape. It is essential for the shape to produce a rotationally fixed mounting. 
   Furthermore, the coupling sleeve  42  has holes  77  with a thread  78  in the end sections  75  and in the cylindrical sections  72 . These holes  77  with threads  78  are used for screwing the coupling sleeve  42  to the frame  43 , as illustrated in  FIG. 5 . 
   The priority application, German Patent Application Nos. 102 41 623.0 and 102 58 479.6 filed on Sep. 4, 2002 and Oct. 12, 2002, respectively, are hereby incorporated by reference herein in their entireties. 
   Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.