Abstract:
A seat restraint tension sensing assembly for a seat restraint system in a vehicle includes a latch plate for connection to belt webbing of the seat restraint system. The seat restraint tension sensing assembly also includes a buckle assembly for receiving the latch plate. The seat restraint tension sensing assembly includes at least one magnet mounted to the latch plate and at least one Hall effect sensor associated with either one of the latch plate and the buckle assembly and cooperable with the at least one magnet. The seat restraint tension sensing assembly further includes a movable actuator mounted to the latch plate and cooperable with the belt webbing to move the at least one magnet relative to the at least one Hall effect sensor to change an output of the at least one Hall effect sensor to indicate a tension level in the seat restraint system.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates generally to seat restraint systems for vehicles and, more particularly, to a seat restraint tension sensing assembly for a seat restraint system in a vehicle.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is known to provide a seat restraint system such as a seat belt in a vehicle to restrain an occupant in a seat of the vehicle. In some vehicles, the seat restraint system may be a lap belt, a shoulder belt, or both. Typically, the lap belt and shoulder belt are connected together at one end. The seat restraint system includes a latch plate at the connected end. The seat restraint system also includes a buckle connected at one end by webbing or the like to vehicle structure. The buckle receives the latch plate to be buckled together. When the buckle and latch plate are buckled together, the seat restraint system restrains movement of the occupant to help protect the occupant during a collision.  
           [0003]    Smart inflatable restraint systems need to know what is occupying a seat of the vehicle. Decisions on deployment of inflatable restraints depend on information supplied by sensors in the seat in determining weight of an object in the seat. When a child seat is placed in the seat and cinched down, the sensors may read a large mass instead of a child seat. With this condition, there will be high tension in the seat restraint system. Comfort studies have shown that no human occupant would wear their seat restraint that tight. With this information on seat restraint tension, the inflatable restraint system can decide on deployment of the inflatable restraint.  
           [0004]    Therefore, it is desirable to sense tension in a seat restraint of a seat restraint system of a vehicle. It is also desirable to provide seat restraint tension sensing for a seat restraint system in a vehicle that allows a control module to determine the difference between a child seat and a small occupant. It is further desirable to provide a tension sensing assembly for a seat restraint system in a vehicle that allows the sensing to occur on either the latch plate or buckle of the seat restraint system.  
         SUMMARY OF THE INVENTION  
         [0005]    It is, therefore, one object of the present invention to provide a seat restraint tension sensing assembly for sensing tension in a seat restraint system of a vehicle.  
           [0006]    It is another object of the present invention to provide a seat restraint tension sensing assembly on a latch plate for sensing tension in a seat restraint system of a vehicle.  
           [0007]    It is yet another object of the present invention to provide a seat restraint tension sensing assembly on a buckle for sensing tension in a seat restraint system of a vehicle.  
           [0008]    To achieve the foregoing objects, the present invention is a seat restraint tension sensing assembly for a seat restraint system in a vehicle including a latch plate for connection to belt webbing of the seat restraint system. The seat restraint tension sensing assembly also includes a buckle assembly for receiving the latch plate. The seat restraint tension sensing assembly includes at least one magnet mounted to the latch plate and at least one Hall effect sensor associated with either one of the latch plate and the buckle assembly and cooperable with the at least one magnet. The seat restraint tension sensing assembly further includes a movable actuator mounted to the latch plate and cooperable with the belt webbing to move the at least one magnet relative to the at least one Hall effect sensor to change an output of the at least one Hall effect sensor to indicate a tension level in the seat restraint system.  
           [0009]    One advantage of the present invention is that a seat restraint tension sensing assembly is provided for a seat restraint system in a vehicle. Another advantage of the present invention is that the seat restraint tension sensing assembly senses tension in the seat restraint system to help identify what is occupying the seat, either a child, child seat, or low mass adult. Yet another advantage of the present invention is that the seat restraint tension sensing assembly allows for optimal location of tension monitoring and communication of a resultant signal either through inductive coupling or direct measurement in the buckle or a magnet displacement in a tongue of the latch plate. Still another advantage of the present invention is that the seat restraint tension sensing assembly can perform a secondary function as seat latch indicators that are activated by coins placed in the buckle. A further advantage of the present invention is that the seat restraint tension sensing assembly has wire routing that follows industry practice and has improved electrical connection. Yet a further advantage of the present invention is that the seat restraint tension sensing assembly is mounted to a seat restraint buckle of the seat restraint system and provides seat belt latching verification and communication with seat belt tension sensing.  
           [0010]    Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of seat restraint tension sensing assembly, according to the present invention, illustrated in operational relationship with a seat restraint system of a vehicle.  
         [0012]    [0012]FIG. 2 is a fragmentary elevational view of the seat restraint tension sensing assembly of FIG. 1 illustrating a pre-latched condition.  
         [0013]    [0013]FIG. 3 is a view similar to FIG. 2 illustrating the seat restraint tension sensing assembly in a latched condition having a low-tension condition and a high-tension condition.  
         [0014]    [0014]FIG. 4 is a fragmentary elevational view of another embodiment, according to the present invention, of the seat restraint tension sensing assembly of FIG. 1 illustrating a pre-latched condition.  
         [0015]    [0015]FIG. 5 is a view similar to FIG. 4 illustrating the seat restraint tension sensing assembly in a latched condition having a low-tension condition and a high-tension condition.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring to the drawings and in particular FIG. 1, one embodiment of a seat restraint tension sensing assembly  10 , according to the present invention, is shown for a seat restraint system, generally indicated at  12 , in a vehicle (partially shown), generally indicated at  14 . The vehicle  14  includes a vehicle body  16  and a seat  18  mounted by suitable means to vehicle structure (not shown) such as a floorpan in an occupant compartment  20  of the vehicle body  16 . In this embodiment, the seat  18  is a front seat of the vehicle  14 . It should be appreciated that the seat  18  could be a rear, second row, or third row seat for the vehicle  14 .  
         [0017]    Referring to FIGS. 1 through 3, the vehicle  14  includes the seat restraint system  12  for restraining an occupant (not shown) in the seat  18 . The seat restraint system  12  includes a latch tongue or plate  22  connected to an end of either one of a lap belt, shoulder belt, or both  23  which have another end connected to a retractor (not shown). The seat restraint system  12  also includes a buckle assembly  24  connected by suitable means such as belt webbing  26  to vehicle structure. It should be appreciated that the latch plate  22  is engageable and disengageable with the buckle assembly  24 . It should also be appreciated that, except for the seat restraint tension sensing assembly  10 , the seat restraint system  12  and vehicle  14  are conventional and known in the art.  
         [0018]    Referring to FIGS. 1 through 3, the seat restraint tension sensing assembly  10 , according to the present invention, includes the latch plate  22  and buckle assembly  24 . The latch plate  22  has a housing portion  28  and a tongue portion  30  extending longitudinally from the housing portion  28 . The housing portion  28  has a cavity  32  therein and an aperture  34  extending therethrough and communicating with the cavity  32  to allow belt webbing of the seat belt  23  to extend therethrough. The tongue portion  30  is generally rectangular in shape and has an aperture  36  extending therethrough and is engageable and disengageable with the buckle assembly  24 . The housing portion  28  and tongue portion  30  are made of a rigid material such as metal. It should be appreciated that the housing portion and tongue portion  30  are a monolithic structure being integral, unitary, and one-piece.  
         [0019]    The buckle assembly  24  has a housing  38  with an open forward end  40  and an opposite rearward end  42  attached to the belt webbing  26 . The buckle assembly  24  also includes a release or push button (not shown) slidably mounted to the housing  38  for movement with respect thereto. The release button is spaced so as to define a rectangular slot-like passage  43  therebetween at the open forward end  40  of the housing  38 , to allow access of the latch plate  22  into the buckle assembly  24 . The buckle assembly  24  includes a movable latching pawl or locking member  44  connected to the housing  38 . The locking member  44  moves between a latched or buckled position of FIG. 3 in which an integral dependent lock bar  46  engages or is disposed in the aperture  36  of the latch plate  22  and an unlatched or unbuckled position of FIG. 2 in which the lock bar  46  is disposed out of or disengages the aperture  36  in the latch plate  22 . The buckle assembly  24  also includes a spring  48  such as a helical coil spring which is located between the locking member  44  and the housing  38  to urge the lock bar  46  into the passage  43  provided for the latch plate  22 . It should be appreciated that the buckle assembly  24  may be similar to that disclosed in U.S. Pat. No. 5,271,129 to Clarke et al.  
         [0020]    The seat restraint tension sensing assembly  10  includes at least one, preferably a plurality of springs  50  disposed in the cavity  32  of the housing portion  28  of the latch plate  22 . The springs  50  are of a coil type. The springs  50  cooperate with an actuator  52  to be described and are arranged to provide balance to the actuator  52 . The springs  50  are made of a spring material. The springs  50  are tuned to a predetermined force such as for comfort or low tension in the seat restraint system  12 . The springs  50  may also be of a leaf type. It should be appreciated that the springs  50  are arranged to prevent internal tipping of the actuator  52 .  
         [0021]    The seat restraint tension sensing assembly  10  includes a movable actuator  52  disposed in the cavity  32  of the housing portion  28  adjacent the springs  50  for cooperating with the springs  50 . The actuator  52  is generally cylindrical in shape and extends laterally. The actuator  52  has an outer surface  54  having a generally arcuate shape to contact the belt webbing  23 . The actuator  52  is made of a rigid material such as plastic. It should be appreciated that, as the tension is increased in the belt webbing  23 , the contact force of the actuator  52  increases. It should also be appreciated that actuator  52  moves as the springs  50  are compressed.  
         [0022]    The seat restraint tension sensing assembly  10  includes at least one, preferably a plurality of magnets  56  disposed in the cavity  32  of the housing portion  28 . The magnets  56  are connected to a carrier  58  extending longitudinally from the actuator  52 . The seat restraint tension sensing assembly  10  includes at least one, preferably a plurality of Hall effect sensors  60  disposed in the cavity  32  of the housing portion  28  and spaced longitudinally from the magnets  56 . The seat restraint tension sensing assembly  10  includes at least one, preferably a plurality of transmission or inductive coils  62  disposed at the open forward end  40  of the housing  38  of the buckle assembly  24  for a function to be described. It should be appreciated that the actuator  52  compresses the springs  50  and this motion moves the magnets  56  farther away from the Hall effect sensors  60  in a push-push arrangement. It should also be appreciated that the position of the magnets  56  relative to the Hall effect sensors  60  changes the output current of the Hall effect sensors  60 . It should further be appreciated that the Hall effect sensors  60  are mounted on a circuit board (not shown) connected to the housing portion  28  and are potted and connected by electrical leads or wires to a source of power such as a modulator circuit for power coupling the Hall effect sensors  60 .  
         [0023]    In operation of the seat restraint tension sensing assembly  10 , when the latch plate  22  is not latched with the buckle assembly  24  as illustrated in FIG. 2, no signal is transmitted by the Hall effect sensors  60 . It should be appreciated that the actuator  52  of the seat restraint tension sensing assembly  10  is spring loaded to an initial position by the springs  50 .  
         [0024]    When the occupant buckles the seat restraint system  12 , the tension in the belt webbing  23  may be lower than a predetermined load required to deflect the springs  50  as illustrated by the solid lines in FIG. 3. In this state, the coils  62  in the buckle assembly  24  inductively transmit power to the electronics in the tongue portion  30  of the latch plate  22 , causing a controller (not shown) to determine that a normal or large mass adult is present in the seat  18 . It should be appreciated that the seat restraint system  12  is in a low-tension condition as illustrated by the solid lines in FIG. 3.  
         [0025]    When a child seat (not shown) is placed in the seat  18  and the seat restraint system  12  is buckled, the seat belt webbing  23  is cinched to pull the child seat tightly into the seat  18 . As the tension is increased in the seat belt webbing  23 , the contact force on the actuator  52  increases. The resistive force of the springs  50  reacts against the increased tension. When the tension in the belt webbing  23  is higher than the predetermined load, the actuator  52  moves as the springs  50  are compressed, thereby moving the magnets  56  farther away from the Hall effect sensors  60  in a push-push-arrangement for a high tension condition as illustrated by the phantom lines in FIG. 3. This changes the output of the Hall effect sensors  60 , causing the controller to determine that a child seat is present in the seat  18 . Depending upon the force applied to the belt webbing  23 , the tongue portion  30  will modulate the signal from the supply side. The coils  62  in the buckle assembly  24  read the modulated signal to infer seat belt tension. It should be appreciated that the seat restraint tension sensing assembly  10  inductively couples to supply voltage and returns the signal from the buckle assembly  24  to the tongue portion  30  of the latch plate  22 . It should also be appreciated that an audible tone or visual indication may be provided when the tension in the belt webbing  23  is increased above a predetermined level. It should further be appreciated that, in another embodiment, the movement of the carrier  58  can be used to create an eccentric rotation of the magnets  56  that modulates the strength of the induced field from the coils  62  located in the buckle assembly  24 .  
         [0026]    Referring to FIGS. 4 and 5, another embodiment, according to the present invention, of the seat restraint tension sensing assembly  10  is illustrated. Like parts of the seat restraint tension sensing assembly  10  have like reference numerals increased by one hundred ( 100 ). In this embodiment, the seat restraint tension sensing assembly  110  eliminates the inductive coils and includes the Hall effect sensors  160  in the open forward end  140  of the housing  138  of the buckle assembly  124 . The seat restraint tension sensing assembly  110  also includes the magnets  156  connected to a slider  158 , which is connected to the actuator  152 . It should be appreciated that the Hall effect sensors  160  are mounted on a circuit board (not shown) connected to the housing  138  and are potted and connected by electrical leads or wires to a source of power such as a modulator circuit for power coupling the Hall effect sensors  160 . It should also be appreciated that the magnets  156  are arranged in a slide by configuration, which will result in adequate output.  
         [0027]    In operation of the seat restraint tension sensing assembly  110 , when the latch plate  122  is not latched with the buckle assembly  124  as illustrated in FIG. 4, no signal is transmitted by the Hall effect sensors  160 . It should be appreciated that the actuator  152  of the seat restraint tension sensing assembly  110  is spring loaded to an initial position by the springs  150 .  
         [0028]    When the occupant buckles the seat restraint system  12 , the tension in the belt webbing  23  may be lower than a predetermined load required to deflect the springs  150  as illustrated by the solid lines in FIG. 5. In this state, the Hall effect sensors  160  and the magnets  156  are disposed next to one another, causing the controller to determine that a normal or large mass adult is present in the seat  18 . It should be appreciated that the seat restraint system  12  is in a low-tension condition.  
         [0029]    When a child seat (not shown) is placed in the seat  18  and the seat restraint system  12  is buckled, the seat belt webbing  23  is cinched to pull the child seat tightly into the seat  18 . As the tension is increased in the seat belt webbing  23 , the contact force on the actuator  152  increases. The resistive force of the springs  150  reacts against the increased tension. When the tension in the belt webbing  23  is higher than the predetermined load, the actuator  152  and slider  154  move as the springs  150  are compressed, thereby moving the magnets  156  farther away from the Hall effect sensors  160  in a push-push arrangement for a high tension condition as illustrated by the phantom lines in FIG. 5. The relative distance between the magnets  156  and the Hall effect sensors  160  changes the output of the Hall effect sensors  160 . Changes in the output of the Hall effect sensors  160  result in corresponding changes of voltage that is transferred to the controller, causing the controller to determine that a child seat is present in the seat  18 . It should be appreciated that the seat restraint tension sensing assembly  110  places magnets  156  in the latch plate  122  and the magnets  156  are displaced in response to the tension in the seat belt webbing  23 . It should also be appreciated that an audible tone or visual indication may be provided when the tension in the belt webbing  23  is increased above a predetermined level.  
         [0030]    Accordingly, in the seat restraint tension sensing assembly  110 , resistance to increased seat belt tension results in the movement of the slider  158  containing the magnets  156  of the latch plate  122 . This movement results in changes in the output of the Hall effect sensors  160  located in the buckle assembly  124 . It should be appreciated that, in another embodiment, a triangular shaped ferrous piece is moved in and out in response to tension of the seat belt webbing  23 .  
         [0031]    The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.  
         [0032]    Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.