Patent Publication Number: US-2005133652-A1

Title: Belt retractor for a vehicle safety belt

Description:
The invention relates to a belt retractor for a vehicle safety belt, with a frame, a belt spool which can receive a safety belt and is arranged rotatably in the frame, and with a blocking mechanism by means of which the belt spool can be blocked against a rotation in the safety belt unwinding direction relative to the frame, the blocking mechanism containing a coupling disc which is rotatable relative to the belt spool.  
     BACKGROUND OF THE INVENTION  
      The blocking mechanism serves in a known manner to block the belt spool in a vehicle-sensitive or belt band-sensitive manner. A vehicle-sensitive blocking is triggered when the accelerations acting on the vehicle and therefore also on the belt retractor, which is mounted therein, exceed a specified value. A belt band-sensitive blocking is triggered when the rotary acceleration of the belt spool, brought about by a rapid withdrawal of the safety belt from the belt spool, exceeds a specified value. In both cases, the blocking is triggered in that a relative rotation occurs between the coupling disc and the belt spool, which is then used to guide a blocking catch into blocking teeth.  
      With the vehicle-sensitive blocking, a sensor is used which, on exceeding the specified acceleration, blocks the coupling disc. If, in this state, safety belt is withdrawn from the belt spool, the coupling disc—because it is secured by the sensor—lags behind the rotation of the belt spool, so that the necessary relative rotation is obtained for guiding the blocking catch. With the belt band-sensitive blocking, the mass moment of inertia of the coupling disc is used to bring about the relative rotation; with a sufficiently high rotary acceleration of the belt spool, the coupling disc lags behind the rotation of the belt spool, whereby the blocking catch can be guided in.  
      The blocking mechanism, however, also possibly responds in situations in which this is not desired. In particular with the rapid winding of the belt band, for example when a vehicle occupant has taken off the safety belt and the safety belt is rolled up under the action of a winding spring, it can occur that the blocking mechanism responds. This is the case in particular when the safety belt is braked abruptly, for example when an insert tongue, situated on the safety belt, butts against another component or the safety belt is fully wound, whereby the belt spool is braked abruptly. Through the abrupt braking, a relative rotation can occur between the coupling disc and the belt spool, so that the blocking mechanism responds. In addition, the risk exists that through vibrations, the sensor on the belt retractor responds, whereby a vehicle-sensitive blocking can be triggered.  
      If belt band is then to be withdrawn from the belt spool, the belt spool is blocked by the blocking mechanism. A vehicle occupant could therefore gain the impression that the belt retractor is defective. The blocking of the belt spool can then only be released by pulling firmly on the safety belt, so that through the film spool effect a small length of safety belt can be withdrawn. In the subsequent freeing of the safety belt, the belt spool is turned back slightly, whereby the blocking mechanism is unlocked.  
      Various precautions are known from the prior art, in order to prevent the undesired blocking of the belt spool at the end of the winding movement. These precautions, however, do not always work satisfactorily; this applies both to their function and also to the effort.  
      The object of the invention consists in further developing a belt retractor of the type initially mentioned to the effect that an undesired blocking of the belt spool at the end of the winding of the safety belt is reliably prevented.  
     BRIEF DESCRIPTION OF THE INVENTION  
      To solve this problem, in a belt retractor of the type initially mentioned in accordance with the invention a locking mechanism is provided which locks a response of the blocking mechanism in a function range in which almost the entire safety belt is wound on the belt spool. The locking mechanism here can neutralize the vehicle-sensitive blocking and/or the belt band-sensitive blocking of the belt spool in line with specific objectives.  
      According to a preferred embodiment of the invention, provision is made that the blocking mechanism has a vehicle-sensitive sensor with a sensor lever, which can engage on the coupling disc, and that the locking mechanism, when it is activated, locks the sensor lever so that the latter can not engage on the coupling disc. In this way, it is reliably prevented that the vehicle-sensitive sensor responds and thereby blocks the coupling disc, which could lead to a vehicle-sensitive blocking of the belt spool.  
      According to a preferred embodiment of the invention, provision is made that the locking mechanism, when it is activated, locks the coupling disc so as to be secure with regard to rotation with respect to the belt spool. This prevents a relative rotation between the coupling disc and the belt spool, so that any response of the blocking mechanism is reliably prevented. In particular, a belt band-sensitive response is not possible, because also with an abrupt acceleration or deceleration of the belt spool, the coupling disc is directly entrained, so that no relative rotation is possible between the coupling disc and the belt spool and accordingly also no response of the blocking mechanism is possible.  
      Advantageous developments of the invention will be apparent from the sub-claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention is described below with the aid of a preferred embodiment which is illustrated in the enclosed drawings. In these:  
       FIG. 1  shows a diagrammatic side view of a belt retractor;  
       FIG. 2  shows in a perspective side view the blocking mechanism of the belt retractor of  FIG. 1 ;  
       FIG. 3  shows in a further perspective side view the blocking mechanism, the coupling disc having been omitted, for better clarity;  
       FIG. 4  shows in a further perspective side view the blocking mechanism, the coupling disc likewise having been omitted;  
       FIG. 5  shows in a perspective side view the components which are necessary for blocking the sensor lever;  
       FIG. 6  shows a perspective view of the locking lever shown in  FIG. 5 ;  
       FIG. 7  shows another side view of the locking lever;  
       FIG. 8  shows in a perspective view one end of the belt spool;  
       FIG. 9  shows in a diagrammatic side view the blocking mechanism, the locking disc having been omitted for better clarity,  
       FIG. 10  shows in a perspective side view the coupling disc arranged on the belt spool;  
      Figure  11  shows a detail of the locking mechanism, the locking lever being situated in the initial position; and  
       FIG. 12  shows the locking mechanism in a diagrammatic view, the locking lever being in the locking position. 
    
    
     DETAILED DESCIPTION OF THE INVENTION  
      In  FIG. 1 a  belt retractor  10  is shown, which has a frame  12  in which a belt spool  14  is rotatably mounted. Only an end face of this can be seen in the figures. This end face can be constructed in one piece with the belt spool, or else as a separate component.  
      A blocking mechanism is provided, which serves to block the belt spool so as to be secure with regard to rotation relative to the frame  12  in case of necessity. The details of the structure and mode of operation of the blocking mechanism are described below only in so far as they are necessary for an understanding of the invention. An essential component of the blocking mechanism is a coupling disc  16 , which is arranged coaxially with the belt spool and is rotatable relative thereto to a limited extent. Through a relative rotation between the coupling disc  16  and the belt spool  14 , a blocking catch (not illustrated), which is arranged in a recess  18  on the end face of the belt spool  14 , is guided into blocking teeth on the frame  12  of the belt retractor  10 . Such a relative rotation can be brought about in a belt band-sensitive manner or in a vehicle-sensitive manner. For a vehicle-sensitive controlling of the blocking mechanism, a sensor  20  is arranged on the frame of the belt retractor, which has a sensor ball  22  and a sensor lever  24 . The sensor lever  24  can be guided into teeth  26  of the coupling disc  16 , so that the coupling disc  16  is blocked against a rotation in the unwinding direction of the safety belt. When the safety belt is withdrawn from the belt spool, the coupling disc  16  remains at a standstill. The relative rotation resulting therefrom between the belt spool and the coupling disc is used to control the blocking catch.  
      A locking disc  28  is provided, which is likewise arranged concentrically with the belt spool. The locking disc  28  is mounted rotatably on a housing part (not illustrated), which is arranged on the frame  12  of the belt retractor  10 . The locking disc  12  is connected with the belt spool  14  by a reduction, which consists of a pinion  29  constructed on the belt spool  14 , a two-stage reduction gear wheel  30 , which is mounted so as to be stationary with respect to the frame  12  of the belt retractor, and of inner teeth  32  which are constructed on the locking disc  28  and extend over approximately 270 degrees. The reduction reduces the rotation of the belt spool  14  to such a great extent that the locking disc  28  carries out a rotation of a maximum of 270 degrees between a state of the belt retractor with fully wound safety belt on the one hand and with fully unwound safety belt on the other hand.  
      A child safety lever  34  is provided, by means of which a child safety function can be achieved. When the child safety function is activated, no belt band can be unwound from the belt retractor; it is merely possible to wind the belt band. Such a function is desirable, for example, in order to fix a child&#39;s seat securely to the vehicle seat. The child safety function is realized in a manner known per se by two trip cams  36 ,  37  on the locking disc  28 , which as a function of the position of the locking disc  28  can adjust the child safety lever between an initial position in which it does not engage on the teeth  26  of the coupling disc  16 , and an activated position in which it blocks the coupling disc  16 , so that on withdrawal of the safety belt a belt band-sensitive blocking is triggered immediately. The two trip cams  36 ,  37  are arranged here so that the child safety function is activated by almost complete withdrawal of the safety belt from the belt spool and is deactivated again by almost complete winding of the safety belt.  
      A locking mechanism is provided, by means of which, as a function of the position of the locking disc  28 , the response of the blocking mechanism can be prevented. The locking mechanism contains, on the one hand, a locking lever  38 , which is arranged in fixed position relative to the frame  12  of the belt retractor and is able to be swivelled between two positions about a bearing  39 , namely an initial position (see  FIG. 11 ) and a locking position (see  FIG. 12 ). The locking lever  38  has a locking extension  40 , which can cooperate with the sensor lever  24 . When the locking lever  38  is situated in its initial position, the locking extension  40  lies at such a great distance from the sensor lever  24  (see  FIG. 11 ) that the sensor lever  24  can be guided into the teeth  26  of the coupling disc  16 . When the locking lever  38 , on the other hand, is situated in its locking position, the locking extension  40 , on the other hand, lies against the sensor lever  24  and presses it away from the coupling disc  16 , so that a guiding in is reliably prevented. An inadvertent response of the sensor  20 , for example by vibrations on winding of the safety belt, is reliably prevented in this way. An inadvertent blocking of the belt spool can not occur. By utilizing the inherent elasticity of the locking extension  40 , the entire sensor  20  can be pre-stressed elastically into its initial position, in which the sensor lever  24  and the sensor ball  22  are placed at rest. A rattling is reliably prevented.  
      On the side facing away from the locking extension, the locking lever  38  is provided with two guide pins  42 , which together with a guide rib  44  form a connecting link guide on the locking disc  28 . The guide rib  44  extends along the periphery of the locking disc  28  and consists of a section arranged radially further outwards and of a section arranged radially further inwards. Between these two sections, a transition section  46  is arranged (see in particular  FIGS. 11 and 12 ). The two sections of the guide rib  44  together with the transition section  46  are arranged on the locking disc  28  so that the locking lever  38  is held in the locking position by cooperation of the guide pins  42  with the section of the guide rib  44  lying further inwards, when almost the entire safety belt is wound on the belt spool  14 . As soon as a comparatively small length of safety belt is unwound, the locking lever  38  is swivelled from the transition section  46  into the position shown in  FIG. 11 , so that the sensor lever  24  is freed and a normal vehicle-sensitive blocking is possible. As soon as the safety belt is almost completely wound again, the locking lever  38  is transferred back into the locking position shown in  FIG. 12 , in which an inadvertent response of the blocking mechanism is prevented.  
      The locking mechanism on the other hand contains a bolt  48  (see in particular  FIG. 8 ), which is mounted so as to be swivellable between an initial position and a locking position on the belt spool  12 . The bolt  48  has a bistable detent mechanism, which is formed by a spring clip  50  having, in the broadest sense, a heart shape, which cooperates with a pin  52 , which is constructed securely on the belt spool  14 . In the centre, the spring clip  50  has an indentation which must slide over the pin  52  when the bolt  48  is transferred form the initial position into the locking position, and vice versa. This ensures that the bolt can not move inadvertently from one position into the other.  
      To move the bolt  48 , a control pin  54  is provided at its free end, which cooperates with a link which is formed by two control ribs  56 ,  57  lying opposite each other, which are constructed on the locking lever  38  opposite the two guide pins  42 , i.e. likewise at the end facing away from the locking extension  40 .  
      In the normal operation of the belt retractor, the bolt  48  is in the initial position shown in  FIG. 9 , in which it does not engage on the coupling disc  16 . The coupling disc  16  can therefore turn relative to the belt spool  14 , which is necessary for the guiding of the blocking catch. The control ribs  56 ,  57  are arranged so that the control pin  54  of the bolt  48 , when the latter is in the initial position, can move through freely between the two control ribs when the locking lever  38  is likewise in its initial position, i.e. the sensor lever  24  is freed. When, on the other hand, the locking lever  38  is in its locking position, the control ribs  56 ,  57  are situated radially further inwards than in the initial position. As soon as the bolt  48 , which turns together with the belt spool  14 , reaches the two control ribs  56 ,  57  the next time on winding of the belt band, the control pin  54  is pressed radially inwards, whereby the bolt  48  is transferred from the initial position into its locking position (see in particular  FIGS. 2 and 10 ). In this position, its free end engages into a window  58  of the coupling disc  16 , so that the latter is locked so as to be secure against rotation relative to the belt spool  14 . In this way it is prevented that the coupling disc, brought about for example by an abrupt braking of the belt spool  14 , rotates relative to the latter and thereby causes the blocking mechanism to respond.  
      As soon as a specified length of the safety belt is unwound from the belt spool, firstly, brought about by the guide rib  44 , the locking lever  38  is transferred from its locking position into the initial position. As soon as the bolt  48  together with its control pin  54  then passes the two control ribs  56 ,  57  of the locking lever  38  the next time, the control pin  54  is pressed radially outwards from the control ribs, whereby the bolt  48  is transferred into its initial position. Thereby, after the sensor  20  has firstly been freed again, the coupling disc  16  is also freed, so that the blocking mechanism can operate again as usual.  
      Through the positioning of the transition section  46  on the locking disc  28  with regard to angle, a setting can be made as to the length of the wound safety belt after which the usual finction of the blocking mechanism is prevented, i.e. firstly the sensor  20  and then the coupling disc  16  are inactivated.  
      According to a simplified embodiment of the invention, the bolt  48  is dispensed with.