Abstract:
A device and method for tensioning a vehicle seatbelt are disclosed. The device has a motor, a pulley, a first cable, and a seatbelt buckle. The motor has a motor output for transferring rotational energy developed in the motor. The pulley is in communication with the motor output for receiving the rotational energy developed in the motor. The first cable has first and second ends. The first end is coupled to the pulley. The seatbelt buckle is coupled to the second end of the cable. The rotation of the pulley causes movement of the seatbelt buckle.

Description:
TECHNICAL FIELD 
   The present invention relates to systems and methods for adjusting seatbelt tension prior to a vehicle impact as well as in non-impact conditions. 
   BACKGROUND 
   Devices for pre-tensioning a seatbelt prior to a vehicle collision have been in existence for many years and under constant development. The tensioning of the seatbelt prior to the sensing of vehicle impact and prior to the pre-tensioning that occurs just before vehicle impact is a more recent development in seatbelt tensioning and is known in the art as “pre-pretensioning”. These systems employ a motorized pre-pretensioning retractor that is activated during pre-impact situations and/or in non-impact situations when the sensing system initiates a vehicle pre-impact signal. 
   Early tensioning of the seatbelt can improve occupant kinematics during a vehicle collision and help reduce or prevent injury to an occupant. Another advantage of pre-crash/impact tensioning of the seatbelt is the tactile feedback that a driver receives from the seatbelt that warns the driver to take action. Pre-pretensioning devices are reversible allowing for early activation prior to impact and in cases where impact does not occur, the system returns to a normal tensioning level. 
   U.S. Pat. No. 6,616,186 issued to NSK Autoliv discloses systems and methods for undertaking pre-pretensioning and is hereby incorporated by reference. Further, U.S. Pat. No. 6,616,186 discloses systems having multiple belt tensioning devices and a motor driven retractor and is hereby incorporated by reference. 
   While current pre-pretensioning devices and methods for pre-pretensioning a vehicle seatbelt achieve their intended purpose, many enhancements and additional features are needed. Therefore, a new and improved pre-pretensioning system and method would be desirable. 
   SUMMARY 
   In an aspect of the present invention a device for tensioning a vehicle seatbelt is provided. The device has a motor, a pulley, a first cable, and a seatbelt buckle. The motor has a motor output for transferring rotational energy developed in the motor. The pulley is in communication with the motor output for receiving the rotational energy developed in the motor. The first cable has first and second ends. The first end is coupled to the pulley. The seatbelt buckle is coupled to the second end of the cable. The rotation of the pulley causes movement of the seatbelt buckle. 
   In another aspect of the present invention, the device further includes a second cable, wherein the second cable has a second cable first end and a second cable second end. 
   In still another aspect of the present invention, the second cable first end is coupled to the motor output. 
   In still another aspect of the present invention, the second cable second end is coupled to the pulley. 
   In still another aspect of the present invention, the second cable second end further includes a spline that engages a ring gear in the pulley. 
   In still another aspect of the present invention, the device further includes a spindle disposed through a bore in the pulley for slidably engaging and supporting the pulley. 
   In still another aspect of the present invention, the device further includes an attachment bracket for securing the pulley to a vehicle structure. 
   In still another aspect of the present invention, the device further includes a torsion member having a first end disposed within a bore in the spindle and a second end disposed within an aperture in the attachment bracket. 
   In still another aspect of the present invention, the device further includes a pyrotechnic pretensioner coupled to the pulley. 
   In still another aspect of the present invention, the pulley further includes a ball track for receiving a plurality of balls injected by the pyrotechnic pretensioner thereby causing the pulley to rotate. 
   In yet another aspect of the present invention, a method for tensioning a vehicle seatbelt is provided. The method includes detecting a pre-impact condition, activating a first device connected to the vehicle seatbelt to tension the vehicle seatbelt if the pre-impact condition has been detected, determining whether a second device for tensioning the vehicle seatbelt has been activated within a predefined period of time, determining whether the predefined period of time has elapsed, and releasing the tension on the seatbelt if the second device has not been activated within the predefined period of time and the pre-impact condition has not been detected after the predefined period of time has elapsed. 
   In yet another aspect of the present invention, the method further includes determining whether the vehicle ignition has been activated. 
   In yet another aspect of the present invention, the method further includes determining whether the vehicle seatbelt is buckled. 
   In yet another aspect of the present invention, the method further includes determining whether the vehicle is stable. 
   In yet another aspect of the present invention, the method further includes activating a warning if the vehicle is determined to be unstable. 
   In yet another aspect of the present invention, the method further includes determining a state of a vehicle transmission. 
   In yet another aspect of the present invention, the method further includes determining a position of a seatbelt buckle. 
   In yet another aspect of the present invention, the method further includes activating a motor to change the position of the seatbelt buckle based on the determined position. 
   In yet another aspect of the present invention, the method further includes monitoring a current supplied to the motor. 
   In yet another aspect of the present invention, the method further includes comparing the monitored current to a current limit threshold. 
   In yet another aspect of the present invention, the method further includes deactivating the motor when the current has reached the current limit threshold. 
   These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a seatbelt buckle pre-pretensioner with an integrated roto-pretensioning device, in accordance with an embodiment of the present invention; 
       FIG. 2  is an exploded perspective view of the device shown in  FIG. 1 , in accordance with an embodiment of the present invention; 
       FIG. 3  is a flow diagram illustrating the method of operation of a system utilizing the pre-pretensioning device shown in  FIG. 1 , in accordance with an embodiment of the present invention; 
       FIG. 4  is a flow diagram illustrating an alternate control strategy for providing pre-pretensioning as well as standard pretensioning of a vehicle seatbelt, in accordance with an embodiment of the present invention; 
       FIG. 5  is a flow diagram illustrating an alternate control strategy for providing pre-pretensioning of a vehicle seatbelt, in accordance with an embodiment of the present invention; and 
       FIG. 6  is a flow diagram illustrating a method of operation of a system utilizing the pre-tensioning device shown in  FIG. 1 , in accordance with an embodiment of the present invention. 
   

   DESCRIPTION 
   Referring now to  FIG. 1 , a device  10  for tensioning a vehicle seatbelt is illustrated, in accordance with an embodiment of the present invention. Device  10  may include an integrated roto-pretensioner  12 . Generally, device  10  has an attachment plate  14 , a seatbelt buckle  16  and a motor  20 . Attachment plate  14  secures device  10  to a vehicle structure (not shown), i.e. a vehicle seat. The seatbelt buckle  16  functions as a traditional seatbelt buckle in that it receives and locks a seatbelt latch plate therein. Seatbelt buckle  16  is securely attached to a flexible cable  18  that secures buckle  16  to attachment plate  14  as will be described below. Motor  20  is provided to drive a flexible cable  22  that in turn causes cable  18  to retract or protract from attachment plate  14 . 
   Referring now to  FIG. 2 , an exploded view of device  10  is provided to illustrate the internal components of device  10 , in accordance with an embodiment of the present invention. Device  10 , generally, includes two mechanisms for adjusting the length of buckle cable  18 . The first mechanism is roto-pretensioner  12  for pretensioning the seatbelt webbing by rapidly retracting buckle cable  18  when a vehicle collision is detected and the second mechanism is a pre-pretensioning mechanism  59 . Roto-pretensioner  12  is preferably a pyrotechnic pretensioner that includes a ball tubs  30 , balls  31  and ball catch  32 . Ball tube  30  and ball catch  32  are sandwiched between and held in place by an end plate  34  and an intermediate plate  36  forming a roto-pretensioner assembly  12 . Assembly  12  is secured to attachment plate  14  using a plurality of screws, bolts or the like  40 . Spacers  42  and  44  are used to provide the proper spacing between intermediate plate  36  and attachment plate  14 , i.e. to accommodate a pulley  38  therebetween. 
   Pulley  38  receives buckle cable  18 . Buckle cable  18  is wound around pulley  38  and disposed within a pulley channel  50 . At an end  52  of buckle cable  18 , a barrel member  54  is attached. Barrel member  54  engages a slot  56  disposed in pulley  38 . The engagement of barrel member  54  with slot  56  in pulley  38  securely fixes end  52  of cable  18  to pulley  38 . Integrally connected to pulley  38  is a rotary ball track  58 . Rotary ball track  58  cooperates with ball tube  30  and balls  31  that are injected into ball tube  30  and along rotary ball track  58  causing pulley  38  to swiftly rotate. The swift rotation of pulley  38  causes cable  18  to rapidly wind around pulley  38  within channel  50 , thus reducing the length or height of buckle  16  relative to attachment plate  14 . The reduction in length of buckle cable  18  in turn tensions the seatbelt webbing attached to the locking plate (not shown) that is engaged with buckle  16 . 
   Pre-pretensioning mechanism  59  contained within device  10  will now be described with continuing reference to  FIG. 2 , in accordance with an embodiment of the present invention. Pre-pretensioning mechanism  59  includes motor  20 , motor cable  22  and pulley  38 . Pulley  38  includes an outer ring gear  60  having internal teeth that cooperates with a spline gear  62  on the end of motor cable  22 . More specifically, spline  62  extends through aperture  64  in attachment plate  14  and engages the internal teeth of outer ring gear  60 . In operation, motor  20  is activated and rotates motor cable  22  and spline gear  62  causing subsequent movement of pulley  38  through meshed interaction of spline  62  with outer ring gear  60 . As pulley  38  is rotated, the length of buckle cable  18  is either extended or reduced depending on the direction of rotation. Rotational movement of pulley  38  in the clockwise direction reduces the length of buckle cable  18  while rotational movement of pulley  38  in the counter-clockwise direction lengthens buckle cable  18  or increases the height of buckle  16  relative to attachment plate  14 . 
   Device  10  further includes a load limiting mechanism to allow buckle  16  to protract from attachment plate  14  after a prescribed loading on the seatbelt is reached during a vehicle collision. The load limiting mechanism includes a spindle  70  that is threaded through an aperture  72  disposed in pulley  38  to rotationally support pulley  38 . Spindle  70  includes a first spindle end  71  and a second spindle end  73 . The load limiting mechanism further includes a torsion bar  74  that has a first end  76  that mates with a cooperating at first spindle end  71  with bore  80  disposed in spindle  70  and a second end  78  that matingly cooperates with an aperture  82  disposed in attachment plate  14 . Thus, first end  76  of torsion bar  74  is rotationally fixed with spindle  70  and second end  78  of torsion bar  74  is rotationally fixed and support by attachment plate  14 . Second spindle end  73  of spindle  70  is matingly received and supported by an aperture  83  in end plate  34 . 
   A pair of lock pawls  84  and  86  are mounted within an inboard of outer ring gear  60  by a pair of mounting screws or bolts  88  and  90 . Locking pawls  84 ,  86  are inertial members that upon swift rotational acceleration rotate into a spline gear  92  dispose at first spindle end  71  on spindle  70 . Thus, in operation, when pulley  38  is swiftly accelerated, locking pawls  84  and  86  are rotated into spline gear  92  thereby locking and rotationally fixing pulley  38  with respect to spindle  70 . 
   Referring now to  FIG. 3 , a control strategy  100  for controlling a system having device  10  is illustrated in flowchart form, in accordance with an embodiment of the present invention. The control method  100  is initiated when a driver enters the vehicle, as represented by block  200 . The seatbelt buckle, at this point, will already be in the “presented” state, which means that it is raised and in a higher position than it would be when the seatbelt is buckled and in use. The driver buckles the seatbelt by inserting the seatbelt latch plate into the buckle. This is done more easily since the seatbelt buckle is at a higher position, relative to the seat. At block  202  the ignition of the vehicle engine is monitored. If the driver does not start the ignition, then the system returns to block  200  and the ignition (voltage) is checked again. However, if the driver starts the ignition then, at block  204 , the system determines whether the driver has moved the transmission of the vehicle out of the park position. If the driver has moved the transmission out of park, then motor  20  of device  10  is activated and pulls the buckle downward to a normal seatbelt buckled position or “home” position. Movement of the seatbelt buckle is accomplished by first monitoring the position of the buckle, at block  206 . If the buckle is in the home position then the system returns to block  204 . However, if the buckle is not in the “home” position then the system activates motor  20  to retract the buckle at block  208  and monitors the current draw of the motor, as represented by block  210 . Once a predefined motor current limit has been reached the system determines that the buckle is in the “home” position and stops buckle retraction, as represented by blocks  206  and  210 . If the passenger side is equipped with the same tensioning device  10 , the passenger buckle will be pulled down in unison with the driver side buckle. If the driver returns the transmission to the park position, the buckle will move back up to an extracted position to allow for easy unbuckling of the latch plate from the buckle. 
   After the transmission has been placed back into the park position, the buckle position is monitored to determine the next action to take, as represented by block  212 . If the buckle is extracted or not in the “home” position, then the system returns to block  204 . However, if the buckle is not extracted or in the “home” position then the system extracts the buckle and monitors the motor current, as represented by blocks  214  and  216 . At block  216 , the system determines whether the motor current has exceeded a predefined motor current limit. Once the predefined motor current limit has been reached the system determines that the buckle is in the not “home” position and stops buckle extraction, as represented by blocks  212  and  216 . 
   Referring now to  FIG. 4 , an alternate control strategy  300  is provided for a system that has a pre-pretensioner and a standard pretensioner device (i.e. device  10 ), in accordance with an embodiment of the present invention. The control strategy is initiated, at block  302 , when the driver enters the vehicle. At block  304 , the ignition is checked to determine whether it has been activated. If the ignition has not been activated, the system returns to block  302 . However, if the ignition has been activated, the system checks whether the seatbelt buckle has been fastened, as represented by block  306 . If the seatbelt has been buckled, then at block  308 , the system determines whether the vehicle is unstable. If the system determines that the vehicle is stable, then at block  310   a, b  and  c  the system determines whether an emergency braking, a low vehicle deceleration (low “g”), or a pre-impact condition exists. If none of these conditions exist then the system returns to block  302 . However, if any of they conditions exist, then the system activates pre-pretensioning at block  312 . At block  314 , a counter is activated and at block  316 , the system determines whether the counter has exceeded a predefined threshold X. If the counter has exceeded the predefined threshold X, then the counter is reset at block  318  and the system checks whether the any of the three conditions mentioned above still exist, as represented by blocks  320   a, b  and  c . If the three conditions mentioned above do not exist, then the system releases the buckle and monitors motor current until a motor current limit has been reached, as represented by blocks  322  and  324 . Once the motor current threshold has been reached the system returns to block  302 . 
   If, however, at block  316 , the timer has not reached the predefined threshold X, the system determines whether pyrotechnic pretensioning has been activated, as represented by block  326 . If the system determines that the pyrotechnic pretensioner has not been activated, then the system returns to block  312 . If the system determines that the pyrotechnic pretensioner has been activated, then the system stops, at block  328 . 
   If however at block  308 , the vehicle is determined to be unstable, then the system checks whether the emergency braking, the low deceleration, or pre-impact conditions exist at blocks  340   a, b , and  c . If any of these conditions exist, then the pre-pretensioner is activated at block  342 . A timer is started at block  344  and at block  346  the system determines whether the timer has exceeded a predefined threshold X. If the timer has not exceeded a predefined threshold X′ then the system determines at block  348  whether the pyrotechnic pretensioner has been fired. If the pyrotechnic pretensioner has not been fired, then the system returns to block  342 . However, if the pyrotechnic pretensioner has been fired at block  348 , the system stops as represented by block  328 . 
   If, however, the timer has exceeded the predefined threshold X′, at block  346 , then the timer is reset at block  350  and the system checks whether the any of the three conditions mentioned above still exist, as represented by blocks  320   a, b  and  c . If the three conditions mentioned above do not exist, then the system releases the buckle and monitors motor current until a motor current limit has been reached, as represented by blocks  322  and  324 . Once the motor current threshold has been reached the system returns to block  302 . 
   However, if at blocks  340   a, b  and  c , none of the three conditions exist, then the system activates a support/warning, at block  360 . At block  362 , a timer is activated. At block  364  the system determines whether the timer has exceeded a predefined threshold Y. If the timer has not exceeded a predefined threshold Y, then the system returns to block  308 . However, if the system has determined at block  364  that the timer has exceeded the predefined threshold Y, the timer is reset at block  366  and the system determines whether any of the three conditions exist, as represented by blocks  320   a, b , and  c . If the three conditions mentioned above do not exist, then the system releases the buckle and monitors motor current until a motor current limit has been reached, as represented by blocks  322  and  324 . Once the motor current threshold has been reached the system returns to block  302 . 
   Referring now to  FIG. 5 , an alternate control strategy  400  for a system having a pre-pretensioner for pre-pretensioning a vehicle seatbelt is illustrated in flowchart form, in accordance with an embodiment of the present invention. Control strategy  400  is initiated at block  402  when a driver or passenger enters the vehicle. At block  404 , the system determines whether the ignition has been activated. If the ignition has not been activated, then the system returns to block  402 . However, if the ignition has been activated, then the system monitors the transmission to determine whether it has been moved out of park, as represented by block  406 . If the transmission has been moved out of park, then at block  408  the system determines the current buckle position. If at block  408  the system determines that the buckle is in an extracted position, then the system returns to block  402 . If however, at block  408  the system determines that the buckle position is in an unextracted position then, at block  410 , the system extracts the buckle. At block  412 , the system determines whether a low vehicle deceleration (low “g”), emergency braking, or pre-impact condition exists. If the system determines that none of these conditions exist then the motor current is monitored to determine whether it has reached a motor current limit threshold, as represented at block  414 . If the motor current limit threshold has not been reached then the system returns to block  408 . However, if the system determines that the motor current limit threshold has been exceeded, then the system checks the buckle position, as represented by block  440 . 
   If however, at block  406 , the system determines that the transmission has not been moved out of park, then the buckle position is monitored at block  450 . If the buckle position is determined to be above the “home” position then the system retracts the buckle at block  416 . At block  418 , the system determines whether a low deceleration (low “g”), emergency braking or pre-impact condition exists. If none of these conditions exist, then the system monitors the motor current at block  420 . If the system determines that the motor current has not exceeded a motor current limit, then the system returns to block  416  where the buckle continues to be retracted. However, if at block  420  the system determines that the motor current limit has been exceeded, then the system returns to block  410  where the buckle is extracted. However, if at block  418  the system determines that one of the above-mentioned conditions do not exist, then the system determines whether the buckle has been buckled, as represented by block  422 . If the system determines that the buckle has not been buckled then the system returns to block  402 . However, if the system determines that the buckle is buckled then the pre-pretensioner device is activated, as represented by block  424 . A timer is activated at block  426  and at block  428  the system determines whether the timer has exceeded a predefined threshold X. If the timer has not exceeded a predefined threshold X, then the system determines whether a pyrotechnic pretensioner has been fired, as represented by block  430 . If the pyrotechnic pretensioner has been fired, then the system stops at block  432 . However, if the pyrotechnic pretensioner has not been fired, then the system returns to block  424 . However, if at block  450  the buckle position is determined to be not above home, then the system determines whether a low deceleration, emergency braking, or pre-impact condition exists, as represented by block  452 . If any of the conditions exist then the system returns to block  422 . If however, the system determines that none of these conditions exist then at block  454  the system determines whether the vehicle is stable. If the system determines that the vehicle is stable, then the system returns to block  402 . However, if the system determines that the vehicle is unstable then the system determines whether, at block  456 , the seatbelt is buckled. If the system determines that the seatbelt is not buckled, then the system returns to block  402 . If however, the system determines that the buckle is buckled, then the system activates the support/warning device at block  458 . At block  460  a timer is initiated and at block  462  the timer is checked to determine whether it has exceeded a predefined threshold Y. If the timer has not exceeded the predefined threshold Y, then the system returns to block  452 . If however the system determines that the timer has exceeded the predefined threshold Y, the timer is reset at block  464 . At block  436 , the system determines whether the low G, emergency braking or pre-impact conditions still exist. If these conditions still exist, the system returns to block  424 . If the system determines that these conditions do not exist, then the system releases the buckle, as represented by block  438 . At block  440 , the system determines the buckle position. If system determines that the buckle is in the above home position, then the system returns to block  416 . If the system determines that the buckle is in the home position, then the system returns to block  402 . Finally, if the system determines that the buckle is in the below home position, then the system returns to block  436 . 
   Referring now to  FIG. 6 , an alternate control strategy  500  for controlling a system having a device  10  is illustrated in flow chart form, in accordance with an embodiment of the present invention. The alternate control method  500  is initiated when a driver enters the vehicle, as represented by block  501 . The seatbelt buckle, at this point, will already be in the “presented” state, which means that it is raised and in a higher position than it would be when the seatbelt is buckled and in use. The driver buckles the seatbelt by inserting the seat belt latch plate into the buckle. This is done more easily since the seatbelt buckle is at a higher position, relative to the seat. At block  502  the ignition of the vehicle engine is monitored. If the driver does not start the ignition, then the system returns to the block  501  and the ignition (voltage) is checked again. However, if the driver starts the ignition then, at block  504 , the system determines whether the driver has moved the transmission of the vehicle out of the park position. If the driver has moved the transmission out of park, the system determines whether the buckle is latched, as represented in block  505 . 
   If the buckle is not latched, the buckle position is monitored to determine the next action to take, as represented by block  502 . If the buckle is extracted or not in the “home” position, then the system returns to block  504 . However, if the buckle is not extracted or in the “home” position then the system extracts the buckle and monitors the motor current as represented by blocks  504  and  516 . At block  516 , the system determines whether the motor current has exceeded a predefined motor current limit. Once the predefined motor current limit has been reached, the system determines that the buckle is not in the “home” position and stops buckle extraction, as represented by blocks  512  and  516 . 
   However, if the buckle is latched, movement of the seat belt buckle is accomplished by first monitoring the position of the buckle, at block  506 . If the buckle is in the home position, then the system returns to block  504 . However, if the buckle is not in the “home” position, then the system activates motor  20  to retract the buckle at block  508  and monitors the current draw of the motor, as represented by block  510 . Once a predefined motor current limit has been reached, the system determines that the buckle is in the “home” position and stops buckle retraction, as represented by blocks  506  and  510 . If the passenger side is equipped with the same tensioning device  20 , the passenger buckle will be pulled down in unison with the driver-side buckle. If the driver returns the transmission to the park position, the buckle will move back up to an extracted position to allow for easy unbuckling of the latch plate from the buckle. 
   As any person skilled in the art of systems and methods for adjusting seatbelt tension will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.