Abstract:
A vehicle-sensitive sensor for a belt retractor for vehicle safety belt systems, comprises an inertia body displaceable in case of decelerations and accelerations of the sensor, and a two-armed lever. A first arm of the two-armed lever forms a coupling pawl, and a second arm of the two-armed lever is able to be engaged by the inertia body such that, in case of a displacement of the inertia body, the lever is pivoted so that the coupling pawl is directed into a clutch toothing.

Description:
TECHNICAL FIELD 
     The invention relates to a vehicle-sensitive sensor for a belt retractor for vehicle safety belt systems. 
     BACKGROUND OF THE INVENTION 
     Belt retractors are widely known components of vehicle safety belt systems. The retractors have a belt spool rotatably mounted in a frame and a blocking mechanism in order to block the belt spool against an unwinding of belt webbing in the case of an impact of the vehicle. The blocking mechanism is controlled by means of the vehicle-sensitive sensor responding to accelerations of the vehicle. Known vehicle-sensitive sensors have a coupling pawl in the form of a one-sided lever, under which a steel ball is arranged. The coupling pawl lies on the steel ball with a depression in the form of a spherical segment. If an intense acceleration occurs in the case of a vehicle impact, then the steel ball moves so that the depression in the form of a spherical segment and hence the coupling pawl are raised. The vehicle-sensitive sensor is arranged here beneath the clutch disc, so that on raising the coupling pawl, the end of the latter is guided into the clutch toothing and hence the blocking mechanism is activated. Conventional vehicle-sensitive sensors are only adaptable in a limited manner to various arrangements in the belt retractor. A further disadvantage of conventional vehicle-sensitive sensors lies in that an installation of the belt retractor which is inclined with respect to the structurally given installation position is not possible, because the gravity then engaging obliquely on the steel ball causes a permanent displacement of the steel ball Connected with a permanent blocking of the belt spool. 
     BRIEF SUMMARY OF THE INVENTION 
     Through the invention, a greater flexibility is to be achieved with the arrangement and construction of the vehicle-sensitive sensor for a belt retractor. This is achieved in a sensor which comprises an inertia body displaceable in case of decelerations and accelerations of the sensor, and a two-armed lever. A first arm of the two-armed lever forms a coupling pawl, and a second arm of the two-armed lever is able to be engaged by the inertia body such that, in case of a displacement of the inertia body, the lever is pivoted so that the coupling pawl is directed into a clutch toothing. The provision of a two-armed lever makes possible a substantially more flexible construction of the vehicle-sensitive sensor compared with the prior art. Thus, for example, the distance covered by the end of the coupling pawl, the size and weight of the inertia body and the spatial arrangement of the inertia body in the belt retractor can be easily varied, without having to accept restrictions in the operating reliability. 
     As a further step, provision is made that the sensor has a housing on which the lever and the inertia sensor are mounted and which is arranged in relation to a reference so as to be pivotal about an adjustment axis, with a nose of the coupling pawl, able to be guided into the clutch toothing, lying on the adjustment axis. Such a construction of the vehicle-sensitive sensor provides the precondition for an adjustment of the vehicle-sensitive sensor on differently inclined installation positions of the belt retractor. The sensor can be pivoted as a unit in the belt retractor, without its release values, i.e. the values which are necessary for a displacement of the inertia body, or the distance covered on displacement of the inertia body from the nose of the coupling pawl changing. Furthermore, the installation angle of inclination may now be adjusted in a simple manner. 
     In further development of the invention, provision is made that the nose of the coupling pawl, able to be directed into the clutch toothing, a point on the rotation axis of the lever, and the center of gravity of the inertia body lie on the adjustment axis in the state of rest of the sensor. Thereby, a compact sensor unit results, which only has a small space requirement on a rotation about the adjustment axis. 
     Advantageously the housing is provided with an adjustment cylinder, which is rotatably arranged. The sensor can be arranged for example in a bore of a covering hood before its being fastened to a frame of a belt retractor. An adjustment cylinder also makes possible a rotatable arrangement of the sensor which is simple to produce and in so doing reliable in operation. 
     Furthermore, provision is made that a display- and adjustment device is provided for the pivot position of the housing in relation to the clutch disc. Owing to these steps, a single type of belt retractor can be adjusted to various installation inclinations, for example for various vehicle types. The display- and adjustment device can be arranged here such that the adjustment can be carried out and detected from the exterior. 
     Provision is made that the second arm of the lever lies against the inertia body in the state of rest of the sensor. Each displacement of the inertia body is thereby converted directly into a movement of the coupling pawl, whereby a rapid response of the sensor is achieved. As the second arm of the lever lies against the inertia body, in driving operation also no rattling of the lever can occur. 
     Alternatively, provision is made that the second arm of the lever in the state of rest of the sensor is arranged at a predetermined distance from the inertia body. Here, it is advantageous that the initial displacement of the inertia body is not influenced by friction between the second arm of the lever and the inertia body. The exact adherence to the structurally given acceleration threshold, after which a displacement of the inertia body takes place, is thereby ensured. 
     As a further step, provision is made that the sensor has a housing with a stop in which an arm of the lever abuts in the state of rest. In this way, a constant predetermined distance can be ensured between the arm of the lever and the inertia body. 
     It is advantageous if the inertia body is formed by a ball and the second arm has a ring which surrounds a segment of the ball. The provision of a ring which surrounds a segment of the ball makes it possible that the second arm of the lever engages in the lower region of the ball, in which region the ball also sits on a support. Thereby, further design possibilities are opened up for the vehicle-sensitive sensor. 
     It is advantageous here that the ring has a contact surface facing the ball, which contact surface has substantially the form of a circular conic frustum surface, the generatrix of which is inclined to the central axis of the ring about an angle of approximately 40°. Such a construction of the ring makes possible a low-friction running of the ball onto the ring, so that the acceleration values necessary for guiding the coupling pawl are only negligibly influenced by friction between ball and ring. 
     It is advantageous if the sensor has a housing with a bearing support to support the lever and a ball support to receive the ball. The ball support is formed here advantageously by a circular cylinder with a conical depression in an end face, so that an annular support surface is produced for the ball. Through an annular support surface, the ball remains at rest as long as an acceleration value given by the structural design is not exceeded. As only an annular surface is in contact with the ball, the ball support is not liable to contamination. 
     In further development of the invention, the lever can have at least one bearing edge or two bearing points along its rotation axis. These constructions both make possible a low-friction bearing of the lever and, in so doing one that is simple to produce for example by injection molding. Bearing edges can be mounted in a V-shaped depression, whereas bearing points can be constructed in a conical shape and arranged in likewise conical depressions with a greater taper angle than the bearing points. 
     In an embodiment of the invention, provision is made that the ring arranged on the second arm of the lever is arranged beneath the central point of the ball. A displacement of the ball thereby leads to a downward movement of the second arm and an upward movement of the coupling pawl, so that the sensor can be arranged beneath the clutch disc of the belt retractor. It is advantageous here if the center of gravity of the lever in relation to the rotation axis of the lever lies on the side of the first arm. The ring is thereby urged by gravity in the direction of the ball, so that in the state of rest of the sensor, the abutment of the ring against the ball or, in connection with a stop, a constant distance of the ring from the ball is ensured. 
     Alternatively, provision is made that the ring arranged on the second arm of the lever is arranged above the central point of the ball. Here, a displacement of the ball leads to an upwards movement of the second arm and a downward movement of the coupling pawl, so that a sensor with these features can be arranged above the clutch disc. In order to ensure also here a constant distance from the ring to the ball or an abutment of the ring against the ball, the center of gravity of the lever in relation to the rotation axis of the lever advantageously lies on the side of the second arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective partial view of a sensor according to the invention in accordance with a first embodiment; 
     FIG. 2 shows a partial view, partially in section, of the sensor of FIG. 1; 
     FIG. 3 shows a view similar to FIG. 2 on the occurrence of an intense vehicle acceleration; 
     FIG. 4 shows a view similar to FIG. 2 with an intense vehicle deceleration; 
     FIG. 5 shows a perspective partial view of the sensor of FIG. 1 from a different angle of view; 
     FIG. 6 shows a partial view of a vehicle-sensitive sensor of a second embodiment; and 
     FIG. 7 shows a side view, partially in section, of the sensor illustrated in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective partial view of a belt retractor  10  comprising a sensor according to a first embodiment. The belt retractor  10  has a frame  12  and a conventional belt spool (not shown) rotatably mounted in the frame  12 . Of a conventional blocking mechanism for the selective, non-rotatable blocking of the belt spool to the frame  12 , merely a clutch disc  14  with clutch toothing  16  is illustrated. A covering hood  18  is fastened to the frame  12 , which hood  18  is illustrated partially in section. The vehicle-sensitive sensor  20  is provided to activate the blocking mechanism in the case of intense accelerations or decelerations of the vehicle. The sensor  20  has a metal ball  22  acting as inert mass and has a coupling pawl  24 , which can be directed by a displacement of the ball  22  into the clutch toothing  16  of the clutch disc  14 . The coupling pawl  24  forms here a first arm of a two-armed lever  26 , on the second arm of which the ball  22  engages in the case of a displacement. The two-armed lever  26  is mounted on a sensor housing  28  which in turn is fastened to the covering hood  18 . In order to achieve a low-friction mounting of the lever  26 , the latter has two bearing edges  30  which rest each on the sensor housing  28  in a V-shaped depression. In the housing  28  in addition a ball support  32  is formed, on which the ball  22  lies. The second arm of the lever  26  has at its end facing the ball  22  a ring  34  which surrounds a segment of the ball  22  and is arranged concentrically to the ball support  32 . The coupling pawl  24  is provided with a nose  36  which on a displacement of the ball  22  engages into the clutch toothing  16 . Furthermore, the coupling pawl  24  has a weight  37 , which ensures that the ring  34  lies against the ball  22 . 
     In the side view of FIG. 2, the sensor housing  28 , the two-armed lever  26  and the covering hood  18  are illustrated in section. The sensor housing  28  has at its end facing away from the coupling pawl  24  an adjusting cylinder  38 , which is arranged in a bore in the covering hood  18 . The sensor housing  28  is thereby arranged on the covering hood  18  so as to be rotatable about an adjustment axis  40 . As can be readily seen in FIG. 2, which shows the state of rest of the vehicle-sensitive sensor  20 , the foremost point of the nose  36  of the coupling pawl  24 , the edge of the bearing edges  30  indicated in dashed lines, i.e. the rotation axis of the lever  26 , the center of gravity S of the ball  22  and the longitudinal axis of the adjusting cylinder  38  lie on the adjustment axis  40 . The sensor  20  can thereby be rotated about the adjustment axis  40  and hence can be aligned to the direction of the acceleration due to gravity, without its release characteristics changing. As can be further seen from FIG. 2, a rotation of the sensor  20  about the adjustment axis  40  also does not alter the distance of the nose  36  from the clutch toothing  16  on the clutch disc  14 , because the point of the nose  36  lies on the adjustment axis  40  and, as can be seen in FIG. 1, the point  36  is rounded in a circular shape. Also with the sensor  20  rotated about the adjustment axis  40 , the point of the nose  36  has substantially always the same distance from the toothing  16  of the clutch disc  14 . 
     In FIG. 2 also the second arm  42  of the lever  26  can be seen, which has at its end facing the ball  22  the ring  34 . The ring  34  surrounds a ball segment of the ball  22  and lies with its contact face  46  against the ball  22 . The contact face  46  has the form of a circular frustum surface. A generatrix of this circular frustum surface is inclined here by approximately 40° to the central axis  48  of the ring  34 , which also runs through the center of gravity S of the ball  22 . 
     The ball  22  rests on the ball support  32 , which is formed by a circular cylinder integral with the housing  28 , which cylinder has a conical depression  50  in its end face facing the ball  22 . The ball  22  thereby lies on an annular support surface. 
     FIG. 3 shows a view corresponding to FIG. 2, in which, however the ball  22  owing to an intense vehicle acceleration, for example by a rear impact of a further vehicle, is displaced to the right. In so doing, the ball  22  only then moves in the manner illustrated in FIG. 3, when it is raised partially from the annular support surface of the ball support  32  through the action of the acceleration. With such a movement, the center of gravity S of the ball  22  also shifts upwards. In order to achieve a displacement of the ball  22 , an acceleration is therefore necessary, which exceeds a particular threshold. This threshold can be set by the weight of the ball  22 , the diameter of the ball  22  and also by the diameter of the annular support surface of the ball support  32 . The displacement of the ball  22  illustrated in FIG. 3 leads to the ring  34  being pressed downwards Consequently also the second arm  42  of the lever  26  is pressed downwards, so that the first arm or the coupling pawl  24  moves upwards. Consequently, the nose  36  of the coupling pawl  24  arrives into the region of the clutch toothing  16  of the clutch disc  14 , and with a rotation of the belt spool and hence of the clutch disc  14 , the blocking mechanism for the belt spool is activated. 
     FIG. 4 shows the conditions in the case of an intensive deceleration acting on the vehicle, for example with a frontal impact. Under the action of the intensive acceleration then occurring, the ball  22  is displaced to the left, whereby the ring  34  is pressed downwards. Also, with an intensive deceleration of the vehicle, as shown in FIG. 4, the coupling pawl  24  is thereby deflected upwards and the nose  36  arrives into the region of the clutch toothing  16  on the clutch disc  14 , so that with a rotation of the belt spool the blocking mechanism is activated. 
     The perspective view of FIG. 5 shows, in part from obliquely to the rear, the belt retractor illustrated in FIGS. 1 to  4  and with the sensor according to the invention. It can be seen in FIG. 5 that the adjusting cylinder  38  is accessible from the exterior of the covering hood  18  and has a slit  52  via which, for example with the aid of a screw driver, the sensor  20  can be turned about the adjustment axis  40 . In order to indicate the pivot position of the sensor  20  and of the sensor housing  28 , respectively, in relation to the frame  12  which serves as a reference, and in relation to the clutch disc  14 , the covering hood  18  is provided on the periphery of the bore receiving the adjusting cylinder  38  with a scale  54 . The adjusting cylinder  38  in turn has an arrow  56  which points to the scale  54 . 
     A vehicle-sensitive sensor  60  of a second embodiment is illustrated in FIG.  6 . This sensor  60  is also provided with a ball  62  which lies on a ball support  64  of a sensor housing  66 , which housing is further provided with an adjusting cylinder  68  and a bearing support  70 . Resting on the bearing support  70  is a two-armed lever  72 , which as first arm has a coupling pawl  74  and has a second arm  76 . The lever  72  is mounted on the bearing support  70  by means of two bearing edges  78 , of which only one is to be seen in FIG.  6 . In order to hold the two-armed lever  72  reliably on the bearing support  70  and at the same time to ensure a low-friction mounting, the bearing support  70  is cut in a V-shape, the opening angle of the V-shaped cut of the bearing support  70  being greater than the angle of the bearing edges  78 . The sensor housing  66  has a stop  80  on which the coupling pawl  74  rests. In the state of rest of the sensor  60 , the coupling pawl  74  always lies here against the stop  80 , because the center of gravity SP of the two-armed lever  72  in relation to the rotation axis of the lever  72 , which is established by the contact line between bearing support  70  and bearing edges  78 , lies on the side of the coupling pawl  74 . Through the abutment of the coupling pawl  74  against the stop  80 , consequently in the state of rest of the sensor  60  also the position of a ring  82  is established, which is arranged on the second arm  76  and surrounds the ball  62  and the ball support  64  in parts. 
     The sensor  60  illustrated in FIG. 6 is illustrated partially in section in FIG.  7 . In this sectional view, it can be seen that the ring  82  in the state of rest of the sensor is arranged at a predetermined distance from the ball  62 . This is achieved in that, as explained with regard to FIG. 6, the coupling pawl  74  resting on the stop  80 . A displacement of the ball  62  taking place owing to an acceleration acting on the ball  62  thereby takes place unaffected by any possible friction between the contact surface of the ring  82  and the surface of the ball  62 . The structurally given acceleration threshold, as of which a displacement of the ball  62  takes place, is thereby insensitive to an increase in the friction between the ring  82  and the ball  62 , as can take place for example by the aging of the materials or contamination.